Hum on some MW and HF freq. with new active Loop RX antennas - Page 1
Forum section: electronics / rf-microwave

author: vinlove
author_rank: Frequent Contributor
timestamp: November 28, 2020, 08:57:55 pm
content: Hi AllJust got an active RX loop antenna for MW and HF RX/BCL/SWL purposes for my receivers.The active loops are powered by 5VDC wallwarts psu or rechargeable phone battery 5VDC ouput.Whatever power source it were fed, it gave very severe 60 cycle AC hum on some frequencies.The worst affected bands seem the whole part of MW and also HF 3 - 6Mhz.On some particular frequencies the hum was worse as the receivers were tuned around.On the other antennas such as an indoor dipole and about 20m longwire in the garden, the hum was not problem.So why these active loop antenna is making the radios hum on the reception?The active loop is installed in the attic, where the wire dipole antenna is also installed.They are very in close proximity but the elements are not touching at all.Any ideas? Thanks

author: geggi1
author_rank: Frequent Contributor
timestamp: November 28, 2020, 09:33:45 pm
content: You got two options.1. run the loop on battery power.2. add filter circuit to the DC input for the loop amp.Filter circuit 1. the simple way.The filter circuit can pretty simple. Start with a noise killing toriode scavanged from som kind of power supply or computer gear. Make a bifilar winding 10-15 turns on the toriode and run positive and negative through the bifilar windings. This will probably kill a lot of hum. If the hum is still a problem add some capacitors to the input and output of the bifilar winding. More capacitors can be added to reduce the hum level.Filrer circuit 2. the hard way.Find some equations and schematics and do a propper design.

author: cdev
author_rank: Super Contributor
timestamp: November 28, 2020, 09:56:15 pm
content: While using a battery, not a AC connected power supply to power the loop, make a 1:1 balun -for galvanic isolation. The best kind I have found for this are binocular cores. You should not need many turns, I would start with only three, simply two short wires twisted around one another for a bifilar winding, separating the antenna from the receiver as far as DC is concerned. If the bandwidth or signal isnt strong enough, try more or less turns.the winding goes around the two holes in the two sides of the core so it gets a lot of inductance in a short length, and are closely coupled together.If you don't have a binocular core, use a (ferrite, not iron core) toroid but make sure the two wires are wound around each other and are in this most basic 1:1 ratio. This is separate from any other impedance transformations you have, it shouldn't change anything, just block the noise that rides in on the power line, if you do it right.An alternative that works similarly is to power your receiver off of batteries too.See if that helps.

author: vinlove
author_rank: Frequent Contributor
timestamp: November 29, 2020, 03:12:53 pm
content: I have already tried powering the loop from 5V battery, but it didn't help.I found what the cause for the hum was. It is the Samsung LED TV in the livingroom.When it is off, the hum disappears.When the TV is on, the hum returns with 9+ signal on many frequencies.

author: HB9EVI
author_rank: Frequent Contributor
timestamp: November 29, 2020, 03:47:01 pm
content: it's a myth people still believe in, that a magnetic loop is not prone to receive local noise.it seems you're running the loop indoors, and as you can see, it receives all the garbage in the air, even if you feed it by battery.there are two possibilties:either you modify the active broadband loop to a selective narrow band loop with a capacitive tuning element. that doesn't really solve the problem, but allows you a better s/n ratioor you move the loop out of the domestic noise, best outdoors, as far away as possible from the buildingbaluns are not going to help you, a loop is always a symmetric antenna, so the active component of the antenna has to properly handle the conversion from the symmetric loop to the asymmetric coax feedline. If this is not the case, you can directly throw it out

author: vinlove
author_rank: Frequent Contributor
timestamp: November 30, 2020, 11:23:36 am
content: Yes, Active Loops pick up RFI. As you say, there are not many options to make it better - baluns wouldn't work.But in my case, the hum is coming from the TV downstairs. It seems it is not via power line, because as I told you that I have tried with battery to power the loop, and the hum is still present.Could it be the TV antenna coax also going through the attic, and it is very near to the loop element, and it goes through the roof to the outside of the house on the top of the roof, there is a large TV Yagi. Yes, we still watch the old UHF TV sometimes.

author: HB9EVI
author_rank: Frequent Contributor
timestamp: November 30, 2020, 12:49:38 pm
content: it not required, that the antenna is fed by a mains supply; RF on the main lines is enough, since they can work like antennas ending up in the same result.if the culprit is clear, I'd try a mains filter for the TV set; if the antenna feedline is the problem, you can build a common mode choke for it; simply by turning the antenna cable over a high mu toroid

author: cdev
author_rank: Super Contributor
timestamp: November 30, 2020, 02:14:03 pm
content: For me, I sometimes absolutely need to use a very simple 1:1 rf transformer to isolate my HF receiver from ground loops. This may be because of the way its constructed, see Leif, SM5BSZ's YouTube videos on the Softrock receiver.A balanced loop is fairly immune to ground loops but most loop antennas are not balanced.In my case its likely a common mode noise situation, but its not the same as the usual RF on the feedline issue many hams have when transmitting, for me its a receive only problem. .Quote from: HB9EVI on November 29, 2020, 03:47:01 pmI agree, and although using a loop was much quieter than a long wire antenna, even with a unun, (which also delivered an improvement) I still had/have a lot of noise.QuoteThats good enough for me! I agree we are struggling over semantics.QuoteThats why I am pointing you to this innovative antenna.It depends on the noise. If the noise is getting into your receive chain the only way to tell is to try different approaches to reducing it. This antenna uses a number of different approaches simultaneously.getting the antenna away from the noise is a big and important improvement right there. Using the loop to act as a tuned filter also helps a lot. Usig a balanced feedline to null out common mode noise also helps. Then you also have an antenna that can be rotated with a sharp null.Its worth a try since its so easy to build.The simplest kinds of loops aren't "balanced, usually, and so although they are quieter than many other antennas, they do still pick up CM junk and if that CM junk is referenced to ground and the receiver's job includes amplifying THAT difference, the result is noise.So in that set of circumstances, a balun may indeed help. A balanced loop is substantially better than an unbalanced loop.Check out Chris Trask's two designs for a tuned receiving loop with a preamp.I cant seem to find his original web site on the search engines. But you can find PDFs of these two papers.A Simple Varactor-Tuned Loop Antenna Matching NetworkandA Varactor-Tuned Indoor LoopBoth by C. Trask------

author: HB9EVI
author_rank: Frequent Contributor
timestamp: November 30, 2020, 04:55:18 pm
content: Quote from: cdev on November 30, 2020, 02:14:03 pmI think we are struggling over semantics heremaybe you should once tell us, how your galavanic isolating 1:1 balun looks; because neither the 1:1 voltage balun, nor the 1:1 current balun (common mode choke) are galvanic separations.what you describe is a 1:1 transformer, but such a transformer offers no common mode rejection. that has to be done separately with a 1:1 current balun. this technique is best common practice for RF push-pull power amps (just not with a 1:1 transformer due to the very low Z on the transistor side)

author: A.Z.
author_rank: Super Contributor
timestamp: November 30, 2020, 08:23:01 pm
content: Is that a so called MLA-30 active loop ?If so, then there are some hacks which may turn that antenna into a decent one

author: cdev
author_rank: Super Contributor
timestamp: November 30, 2020, 10:08:26 pm
content: The varactor tuned antenna benefits a great deal from having it's variable DC voltage fortuning come from a multiturn potentiometer with a vernier dial, because otherwise the peak - the small area where its tuned at that moment will just flash right by you. The tuning network is really something. I originally built this antenna and found it received so much signal that I just didnt build the preamp into it, but I was also using it indoors, I never put it in the quiet location it really deserves. But in my rush to get it going I ignored what the antennas main points is, getting the antenna far away from the noise in a modern house. But that noise actually is a big part of my problem. Trasks loop also uses something like Ethernet Cat 5 r 6 cabling as its feed, allowing a balanced feedline thats decoupled from the antenna by both the balanced nature of the transmission line and a ground at the antenna end, and the one way preamp. This prevents the noise leaving the shack and getting to the antenna.The LNA at the antenna end of the system also determines the noise figure exclusively. Even though lots of strong signals were so strong on this loop indoors that the signal had to be greatly attenuated to prevent receiver overload on some of my receiving setups, especially RTLSDR/plus up-converter, I still think in retrospect that the preamp might have been useful because it prevented noise from the shack from making it to the quiet zone around the antenna. Here with the loop hanging right next to me so I could rotate it by hand, I never got the opportunity, going to give it another shot and build an outdoor motor setup to also rotate it, when I can.

author: HB9EVI
author_rank: Frequent Contributor
timestamp: November 30, 2020, 11:46:04 pm
content: varactor tuned loop is an option, though the Q is not as high as with a real variable cap; remote operation of a classic var. cap could be achieved by a grill motor.the question for either solution is, if it's worth it.if it's not possible to place a loop outdoors, a mini whip is certainly a better stealth solution; it can be much easier hidden from nosy neighbors than a loop, but it brings different problems like the question of counterpoise

author: A.Z.
author_rank: Super Contributor
timestamp: December 01, 2020, 09:21:40 am
content: Quote from: vinlove on November 28, 2020, 08:57:55 pmAssuming it's one of those "MLA-30" active loop antennas (likethis one) then the "hum" or more in general the noise may come from the power unit or be picked up by the poor coax used to feed the antenna; if you look at the schematics of the reverse engineered MLA-30hereyou'll see that the power unit (Bias tee) uses a voltage multiplier to raise the 5V fed through the USB port up to 12V, and such a multiplier generates quite a lot of noise; plus the coax used to feed the antenna is of very poor quality and then there's an impedance mismatch between the loop and the preamp input; those issue could be corrected with a bit of soldering, and the result, while not "stellar" would be a decent antennaLet's start from the power feeder; look at the attached circuit, you'll need to cut the traces marked with the red dots, at that point, connect two wires to the traces going to pins #1 and #5 of the USB port and carry them out (or add a connector to the feeder box); done so, the feeder will be powered using a good, NON SWITCHING 12V filtered supply; this will in effect eliminatr the noise generated by the voltage multiplier and improve the antenna performanceWilling to go on, we should now work on the preamp (the one enclosed in the loop box); the preamp is potted and the coax is directly soldered on the board, and unpotting the board would be difficult and could result in a damaged unit, so let's skip it and do what we can; first of all, gently remove the silicon which blocks/seals the coax, done so, we'll cut about 2m of coax, slide it inside the box and use some sealant to close the hole; at this point we'll drill another hole of proper diameter and install a BNC connector, done that, we'll wind the coax around a toroid to form a 1:1 "Guanella" choke and connect the coax to the BNC connector we installed; with this mod we'll then be able to feed the antenna using a better cable (RG-58 or TV/SAT coax will fit)The only remaining issue will now be the impedance mismatch; if you look at the preamp schematic you'll see that the low-pass filter sitting between the preamp input and the loop has a bad impedance mismatch, since it sees pretty high impedance on the preamp side and pretty low on the loop one; now, being unable to act on the circuit (it's potted) the only thing we could do is placing a transformer between the loop and the preamp circuit input, we could wind such a transformer using a #73 binocular core; two turns to the loop, 6 to the preamp; to connect the transformer we will remove the winged nuts/bolts/screws used to lock the loop in place (refer to the image) and fold the two metal contacts down toward the preamp board, done so, we'll reinsert in place the screws/bolts/nuts and connect the transformer between them (the loop contacts) and the metal contacts we folded downWith the above mods, the loop performances will improve quite a bit and offer better reception; willing to further improve the loop, it could then be possible replacing the thin wire forming the loop itself with some thicker wire or piping.

author: vinlove
author_rank: Frequent Contributor
timestamp: December 01, 2020, 04:30:04 pm
content: Yes, it is MLA30. It is a great loop aerial. At times, I get impressed by its performance compared to the other antennas such as longwire or dipoles.But hmmm it has to be modified for combating the hum issue, so will need to have a look at this.When downstairs Samsung plasma TV is off, it is OK. The MLA30 performs great. But XYL watches the TV till about midnight, and the hum kills the radios.

author: A.Z.
author_rank: Super Contributor
timestamp: December 01, 2020, 04:42:13 pm
content: Quote from: vinlove on December 01, 2020, 04:30:04 pmSo the plasma TV is generating noise (either through the power mains or directly on air); you may try adding a line filter (like these) to the plasma TV power connection and maybe a second one to the power supply feeding the loop; in either case, have a look at the mods I suggested, those will improve the loop performances; also, adding a BNC connector will allow you to use a longer coax and place the loop outside (e.g. on a balcony) where it will offer even better performances

author: radiolistener
author_rank: Super Contributor
timestamp: December 01, 2020, 07:17:28 pm
content: Quote from: vinlove on December 01, 2020, 04:30:04 pmshort antenna with amplifier cannot be better or the same effective as proper half wavelength dipole. The reason for that is noise floor limitation.You have noise, because your feeder works as a part of antenna. In order to fix that, there is needs for a good RF choke.

author: A.Z.
author_rank: Super Contributor
timestamp: December 01, 2020, 07:21:56 pm
content: Quote from: radiolistener on December 01, 2020, 07:17:28 pmSure, but what if one can't put out (say) a beverage ? Should (s)he give up ? And, in any case, I believe the topic is different

author: radiolistener
author_rank: Super Contributor
timestamp: December 01, 2020, 07:37:32 pm
content: Quote from: A.Z. on December 01, 2020, 07:21:56 pmI remember that he had PSU issues due to emission from the feeder with another short wave antenna. Now there is active antenna, but the same issue.Here is a video about RF choke, hope it will helps to understand what's going on and how to avoid such issue in the future:

author: vinlove
author_rank: Frequent Contributor
timestamp: December 01, 2020, 08:40:36 pm
content: The old PSU with dead smoothing caps. and Active Loop are totally different cattle of fish. Please don't confuse yourself again.I am going to try a choke to the TV. Active Loops shouldn't needs those usually unless it is is very special circumstances.Converting MLA30 feedline to BNC connector, and make the feeder longer so that it can be install far away from thehouse building seems a great idea.MLA30 is a great performer. It just needs be located at right spot high up for the best performance.

author: cdev
author_rank: Super Contributor
timestamp: December 01, 2020, 10:18:24 pm
content: What happens if you bypass the DC-DC converter, running the loop preamp off a 12v battery?It shouldn't be hard to unplug the USB and using alligator clips splice in a battery just to test out if it gets quieter. Based on my experience with LNAs and USB it might get a lot quieter.LNAs and USB and/or DC-DC converters really don't mix well!Another idea, work on the problem from the TV side. To do this you need to pop the TV open and strip it down to the metal case inside the plastic case.Get some copper tape, open up the TV and then go around bonding the pieces of shielding metal together a bit better than the manufacturer ships it. Also put multiple ferrites - Big ferrite split beads, big ones, on the power cable and any other cables entering the TV, don't skimp on those beads. Use the appropriate kind of material for the frequencies you're operating on. I'd start with a bare minimum of three big ones on each cable, preferably more.You can't overdo it, the more ferrites, the better reception.Despite all this, I still have problems with noise, but, there definitely are lots of things you can do, and every time you fix one source, then you find you have unmasked another slightly weaker one.

author: radiolistener
author_rank: Super Contributor
timestamp: December 02, 2020, 12:13:35 am
content: Quote from: vinlove on December 01, 2020, 08:40:36 pmRF choke is even more important thing for active mini-whip antenna.It become not important if you're using it far away from buildings, any kind of electronic devices (such as TV), mains and high voltage lines.

author: cdev
author_rank: Super Contributor
timestamp: December 02, 2020, 02:57:16 am
content: Yes, definitely.With a PA0FRI mini whip/e-probe type antenna, where you put the chokes (and any grounds) makes an absolutelyhugedifference. You don't want to put chokes where you would with other more conventional antennas, but you do want them before the receiver, also outside before it comes into the house. Actually I roll the coax into a roll and put four huge chokes in a circle enclosing as many turns of wire at the same time as I can.Quote from: radiolistener on December 02, 2020, 12:13:35 am

author: A.Z.
author_rank: Super Contributor
timestamp: December 02, 2020, 08:15:13 am
content: Quote from: vinlove on December 01, 2020, 08:40:36 pmDon't do that alone; consider using the thin coax to wind a guanella choke inside the preamp box, that will help cutting off CMN, then since you're going to open the preamp box to install the BNC, also consider winding and installing the transformer; for the choke, seehere, notice that since it's for an RX only device, you may use a smaller core which may fit the top of the box where there's space to host it and where it could be sticked to the box using a bit of silicon; the choke isn't strictly necessary since the preamp has pretty good CM rejection but... better going for "belt & suspenders"As for the transformer, the schematic is similar to the oneshown here, in our case though the connections will be reversed, the two turns winding goes to the loop and the 6 turns one to the preamp input; such a transformer would bring the input impedance around 200 Ohm and, while there will still be a mismatch, it will be better than the original design which,as G8JNJ wrotehas a bad impedance mismatch; again, no miracles but the modifications will improve things quite a bitThen you may consider the idea to modify the power splitter unit (Bias Tee) by excluding the DC-DC (5V to 12V) converter and directly powering the splitter using a good 12V supply, that mod will greatly reduce the noise at lower frequency and further improve the antenna performancesAt this point, the last step would be moving the antenna outside (roof, balcony, out of a window...) and feeding it with some length of good coax, the latter may be further choked using (e.g.) snap-on #31 ferrite beads; placing (say) 10 of them at the feedpoint, 10 at about 1/2 of the feedline and another 10 at the receiver end should help keeping whatever CM at bayThen, by the way, if the Plasma TV is emitting RF noise "on air", the only solution would be moving the antenna as far from the TV and "in the clear" as possible

author: A.Z.
author_rank: Super Contributor
timestamp: December 02, 2020, 08:20:16 am
content: Quote from: cdev on December 02, 2020, 02:57:16 amWell, it depends; I've played with miniwhips, and if you can use a well grounded metallic pole, you can choke the coax directly at the whip feedpoint; in short, just ensure to install the whip ABOVE the pole (not at a side) and to connect it so that the coax connector ground will have good contact with the (grounded) pole, with such a config, instead of using the coax as a "counterpoise", the whip will use the pole so the coax could be choked as needed; then by the way, it would also be a good idea running the coax "horizontally" away from the pole to minimize coupling

author: vinlove
author_rank: Frequent Contributor
timestamp: December 02, 2020, 08:43:21 am
content: Great ideas and points on the topic there in this thread. Thank you for that.I shall look into this for implementation soon.

author: A.Z.
author_rank: Super Contributor
timestamp: December 02, 2020, 09:06:19 am
content: Quote from: vinlove on December 02, 2020, 08:43:21 amSince you're at that, also consider implementing this modor, either, this onethose are "mechanical" mods, in both cases the original loop is replaced with a larger one which offers better performances; as for installing the BNC connector, refer to thisnotice that the folk used a single snap-on choke; that one alone won't be efficient, better cutting a longer length of coax and winding a guanella choke on a toroid

author: vinlove
author_rank: Frequent Contributor
timestamp: December 02, 2020, 06:34:28 pm
content: Yes, great stuff. Will watch the videos, and take it from there.I still feel at this minute, MLA30 is great Loop Aerial for the money.I bought 2x of them because at the time they were cheaper with the dealsabout 25 euro each.But for night time DXing on 3-6 Mhz, my longwire hears better.All the tropical bands signals from South America, China and Europesounds a lot better and clearer with the longwire and ATU.During the day MLA30 wins hand down. You need 2 - 3 different aerialsfor different time and day, and also for different bands.Switch over all the aerials using the antenna switch, you may thinkthere is no signal on 1 or 2 antennas, you hear very well on the 3rd one.And vice versa.

author: A.Z.
author_rank: Super Contributor
timestamp: December 03, 2020, 11:25:42 am
content: Quote from: vinlove on December 02, 2020, 06:34:28 pmHad an MLA-30 in a past, but gave it to a friend since at my QTH there isn't so much noise, but you raised my curiosity, so I went on and ordered the MLA-30+ (notice the "+") which apparently should have been optimized to improve performances on higher frequencies (where the MLA-30 wasn't exactly good); got the antenna at my door yesterday, unpacked it and, aside from the "+" the antenna looks exactly like the regular one; had no time to test it (yet) and I'll probably give it a check over weekend, then... well, I'll open it and see what's inside and if there are any visible differences with the previous model, the plan will then be to modify the antenna to see where I can bring it tonot expecting miracles, but those 3...4 mods should result in better overall performances

author: vinlove
author_rank: Frequent Contributor
timestamp: December 03, 2020, 02:14:40 pm
content: Quote from: A.Z. on December 03, 2020, 11:25:42 amMine is also + version, and I am not sure what the difference between it and non + version.But yes, it works for me. Not the best antenna under the Sun, or Magic Wands of Harry Potterbut it does the job, and very comparable to full length dipole or longwire.With some mods suggested by yourselves, it will even be better, and has more potential for evenbetter performance.

author: A.Z.
author_rank: Super Contributor
timestamp: December 03, 2020, 04:06:14 pm
content: Quote from: vinlove on December 03, 2020, 02:14:40 pmWell,comparable... it depends; if you live in an "RF noisy" spot, a loop (not just the MLA-30) will give you better reception due to the lower noise level and the ability to null-out noise sources, but if (as in my case) you live in a relatively quiet (from RF standpoint, at least) spot, then there may be better antenna; I've been running some experiments with antennas for "limited spaces", and the last "episode" which my friend Thomas kindly published is this onehttps://swling.com/blog/2020/12/how-to-build-a-simple-linear-loaded-dipole-for-low-noise-shortwave-radio-listening/due to my self-imposed restrictions, the antenna is short (about 9m), but nothing forbids one from building a longer version of it and, sincerely, I believe it's worth a try also since it's really easy and cheap to put togetherQuoteYes, the MLA-30 designer felt short on some aspects and the potting doesn't help, luckily there is enough room to improve the antenna; the main twos in my opinion are the loop itself, which may be replaced with some fatter conductor (or even copper pipe) and the Bias-Tee voltage multiplier which, once excluded, will remove the noise at lower frequencies and allow to pick up weaker signals

author: cdev
author_rank: Super Contributor
timestamp: December 04, 2020, 02:29:52 am
content: Quote from: A.Z. on December 02, 2020, 08:20:16 amI've tried that (grounded pole) and that has never worked well for me. (and I suspect my situation is atypical) I live not that far away from light industrial area, also high tension wires, around a half mile away. These HT wires are strong enough to light a fluorescent tube stuck into the ground beneath them brightly enough to be visible in the daytime. (an artist in the UK makes art installations using fileds of these tubes and they eerily flicker from the electricity in the air.)Heres what I do. My mini whip, when iuts outdoors, (it doesnt work at all indoors, just noise so dont even try it) sits on an old rusty velbon tripod when its outdoors , on top of approximately two meter long PVC pipe that gets put together when I put the antenna and tripod outdoors, I dont leave it out there all the time. No ground wires,I found it hurt. The feedline is currently RG-58 and sometimes I ground it some outdoor ground wires right where it enters thehouse, but right now it isnt. I haven't really decided if it helps. There are a couple of ferrites attached to the coax like beads every couple of feet. There is a bunch of RG-174 at the end crammed through four huge ferrite beads many many times. Then comes the miniwhip bias tee, then comes the 1:1 balun core and the receiver.This is kind of a strange looking system but its actually what works here after lots of trial and error.

author: vinlove
author_rank: Frequent Contributor
timestamp: December 04, 2020, 12:40:38 pm
content: I tried ferrite chokes on the MLA30 feeder but was not very effective, hence thought Active Loops don't work with the chokes. But maybe I was wrong.I also tried an Active Whip from Gareth Spectrum Electronics, and yes, it was unusable set up indoors, even in the attic. It overloaded and over modulated and cross modulated from the RFI and any noise in the space.It must be only to be installed outdoors clear from any source of noise. I am needing a pole for the whip. Either wooden one from the shed or garden if I can find one. If not, in eBay I was looking at a fibre glass extendable pole for flags and fishing 7m long one was about 20 quid. But wan't sure if it will stand the winter gales of 100 miles per hour which will be coming soon.

author: A.Z.
author_rank: Super Contributor
timestamp: December 04, 2020, 01:52:15 pm
content: Quote from: vinlove on December 04, 2020, 12:40:38 pmChokes won't have high enough CM impedance to be effective, given you aren't using 10 or more of them... better winding a "Guanella" style choke using the coax which comes with the MLA-30; but the real problem is the power injector unit, the DC-DC converter generates tons of noise, using a better injector and powering it with a good, stabilized 12V supply will improve things quite a lotQuoteSetting up a whip indoors is seeking for trouble, that antenna wasn't designed for such an application

author: cdev
author_rank: Super Contributor
timestamp: December 04, 2020, 11:52:13 pm
content: At the end of the day I think a miniwhip like the PA0FRI type is perhaps one of the most potentially storm and wind durable antennas out there if you use a study support and its not near any objects that could become airborne and smash into it.The reason I don't leave mine in my backyard all the time is big deer who come through and sooner or later knock down any antenna that's in their path. We even get bucks, once two bucks with antlers literally had a battle in my back yard.A white fiberglass pole is pretty strong though, and visible. There is a sweet spot for fiberglass poles where they are quite tall, but not so tall that they are vulnerable to wind loading from the pole itself that badly. The actual PCB and capacitive area on my miniwhip is quite small, (I just have the basic one from ebay, sold by some Ukrainian guy.)Or use a capped PVC pipe. Then there is no exposed anything. If its secured to the ground well, that would likely survive a hurricane. It doesn't have to be up as high as most antennas do, because of how it works, it just has to be away from noise sources, and up a bit, the more isolated it is the better it works, especially on lower frequencies.The best source of info on them is PA0FRI's web writeup on his site. That antenna really needs to be outdoors.As a point of comparison for indoor use, right now I am using a 43 foot long length of wire in my attic connected to a 9:1 ferrite unun, using most of the coax feedline as the counterpoise, again with common mode chokes and the 1:1 transformer arrangement. This receives fairly well, with the noise issue I mentioned earlier. In comparison a PA0FRI miniwhip located at the same spot as the 9:1 unun is now performed really badly, but when I put it outdoors on the roof, just a few feet away, by running the cable outdoors through a skylight, and just propping it off the roof a bit with a piece of wood and some screws, to hold it off the shingles ust to try the experiment out, it worked fine. Basically, it just needed to be stuck up into the air.It does work much better away from the house. The common mode chokes are mostly near and at the absolute end at the receiver side, not at the antenna end of the coax at all.The wood in the house basically blocked the (e-field?) signal.Aforementioned mag loop, in the same general area, in the attic worked fine, but it worked just as well downstairs. .Quote from: vinlove on December 04, 2020, 12:40:38 pmI would get a cheap pole and when you anticipate stormy weather lower it so the top sections are inside it and giving it strength instead of height. If it breaks, it breaks, but it probably won't.For use with a mini whip and generally for flexibility, I would make sure you get a fiberglass one and not a carbon fiber resistor instead!I made an embarassing mistake recently, I had bought a really cheap carbon fiber casting reel for antenna casting use but I was at that moment using it to try to tune up an innovative two band gain hybrid j-pole, which uses a coax stub and precise lengths and there are several slightly different versions, depending on if it lives inside a PVC pipe or simply hangs from a tree or something. But I was trying to tune it indoors. because it was there and I wasnt thinking I was trying to use the fishing pole in my kitchen to hold it as far away from everything, but it just wasnt working right. (I was using my brand new nanovna2 to guilde my adjustments. It was a long time before I realized it was the fact that being a carbon fishing pole (that cost all of $7) the pole had a substantial effect on the tuning. So I bot the bullet and attached a tiny hook to a drywall anchor in the ceiling and used a foot or so of fishing line to suspend it and then I was able to tune it right in just fifteen minutes. the fishing pole really made a big difference.

author: vinlove
author_rank: Frequent Contributor
timestamp: December 05, 2020, 09:44:14 pm
content: Yup, the mini whip was the only HF antenna which goes crazy indoors. All other HF antennas sort of worked indoors even a piece of wire works in the room near the window. The mini whip absolutely goes crazy with over modulation and over loading in the room even near the window. I thought the mini whip was faulty. I put it up in the loft attic, and it was the same. Then I read about the mini whip = no no indoor antenna no no.So, I am planning to put it out in the garden. But my problem is, that the only place I can put it up is, on the garden shed roof. But it is problem, because it is just too far from my radio room. The coax is firmly attached in the mini whip radiator inside the pole and sealed, it cannot be detached, and replaced with a longer coax feeder.So it must be installed near the house building maybe tied on the gutter pipe? But the house is over 7 m high, so the 7m fibre glass pole from eBay would not clear the roof, which will block the signals from the North. This is another problem. And anything over 7m pole (10m) is twice more expensive, and I am sure it will definitely snap break into two during the winter gale time here.But somehow it must go out. I am thinking of installing the mini whip on the shed, and add more coax feeder on the existing short coax (about 4m long), and bring the coax feeder into the window of the room. This is not a tidy or perfect solution, but maybe a way to see it working?

author: cdev
author_rank: Super Contributor
timestamp: December 06, 2020, 02:06:01 am
content: The bottom of the pipe can be open?Or just plug it up with something space occupying. Some soft foam or some bubble wrap. To keep the bugs out.

author: A.Z.
author_rank: Super Contributor
timestamp: December 06, 2020, 10:44:41 am
content: since you also have a miniwhip, did you try powering the mla-30 through the miniwhip bias tee unit ?

author: vinlove
author_rank: Frequent Contributor
timestamp: December 06, 2020, 11:25:36 am
content: No, bottom of the radiator part of the mini whip is sealed with the coax cable inserted into it. Once I tried to unscrew the plastic connector of the coax, but it was just rotating itself endless not coming off. But I will try it again. It is this one here. Exact same.https://www.ebay.co.uk/itm/Compact-Coil-Active-Antenna-DC-500kHz-30MHz-Made-in-Dorset-UK/283347768970?hash=item41f8d7d68a:g:fisAAOSwuOdcRf-INo, the connector between the RX to the mini whip BIAS box is RCA type, not the same connector as the MLA30 mobile phone charging connector type, so hadn't tried it yet. And to the antenna, it is a BNC connector.I didn't see any adaptor for RCA or BNC to the mobile phone charging connector. Maybe have to open the boxes and rewire them?Looking at the photo of the item, it seems slightly different on the connectors and also the power lead (it now has the fuse in line, mine doesn't have the fuse in line).

author: cdev
author_rank: Super Contributor
timestamp: December 06, 2020, 02:23:19 pm
content: Ouch.I think you're right to want to mount it differently.Assuming that is an e-field probe antenna, its not built properly if it comes with that side mount because it works via capacitanceand so its capacitive surface needs to be inserted into the e-fieldwhich means sticking out and away from other conductors, even very resistive ones.Usually the capacitive surface is just a square a few cm2of copper on the top of the PCB.-----Lots of additional info on placement of an e-field probe antenna and noise is easy to find, if you name it properly.http://dl1dbc.net/SAQ/Mwhip/Article_pa0rdt-Mini-Whip_English.pdfhttp://www.pa3fwm.nl/technotes/tn09d.html(Earlier I misidentified the maker of the best known e-field probe design -While looking onPA0FRI's web site for the e-field probe description and experiments I realized the miniwhip isactuallymade byPA0RDT. Sorry.But while there I found these plans for an shielded active broadband shielded loop that can be made with an off the shelf MMIC and other components. Looks interesting and useful for noise elimination.https://pa0fri.home.xs4all.nl/Ant/Active%20antenna/Active%20receiving%20%20loop%20antenna%20eng.htm

author: vinlove
author_rank: Frequent Contributor
timestamp: December 06, 2020, 02:43:08 pm
content: Yes, true.It seems quite popular active mini whip, because it gets sold a lot, and the reviews seem all very positive.I was not aware of the design, how to install / setup or performance of it. I got it a 2nd hand one for cheap.It was a 2nd hand one, but was never used - still in the original packing.There was a instruction sheet with it, but it never mentions how to install or set up.It just says, that it must be fed with high quality linear psu otherwise it will be very noisy.

author: cdev
author_rank: Super Contributor
timestamp: December 06, 2020, 03:45:36 pm
content: The current all these antennas use is so low that its best to feed them with a rechargeable (a lead acid battery works well for this) and recharge it every few days.The difference between the two can be substantial. I have a very low noise PS, and it seems that even though the PS has practically no ripple, the noise is actually caused by the fact that the AC power line serves to introduce unavoidable noise if its used.In theory if you had a perfect ground this would likely not be a problem, but, for example, where I live, the grounding is well known to be horrible. Because of volcanic rocks, which are not conductive. Maybe that is why its so noisy here at least in part?

author: A.Z.
author_rank: Super Contributor
timestamp: December 06, 2020, 05:00:39 pm
content: Quote from: A.Z. on December 06, 2020, 10:44:41 amok, tried it, just needed a sma-bnc adapter (didn't yet put a bnc on my mla-30+) the effect on noise is pretty impressive, the bias tee of the miniwhip was powered using a stabilised PS and since there's no voltage multiplier it's much quieter, and that confirms (not that it was needed) the fact that the mla-30 bias tee unit is VERY NOISY

author: cdev
author_rank: Super Contributor
timestamp: December 06, 2020, 11:43:52 pm
content: The rtl-sdr also contains an internal DC-DC converter and it perhaps shuld be done if somebody want a significant noise improvement.The guy who built the first nanovna has (It was a while ago- also in Japanese, so must translate) a web site where he systematically explored the effects of doing all these small improvements to the rtlsdr.For example, its possible to replace one of the DC-DC converters pretty easily with three diodes, which significantly reduces the noise floor.Quote from: A.Z. on December 06, 2020, 05:00:39 pm

author: vinlove
author_rank: Frequent Contributor
timestamp: December 10, 2020, 02:07:37 pm
content: Got some pack of cheap ferrite chokes from Amazon, and fitted onto the Samsung plasma TV power lead to the mains and the aerial coax to the antenna socket. After all that, still had left with about 10 of the ferrite chokes, so rest of them were fitted onto the radio PSU leads and MLA30 feed leads etc, and WOW. It really works. Almost no hum on the HF and MW RXing at all. The problem sorted. No hums. The Ferrite Chokes worked !! Thanks !!

author: A.Z.
author_rank: Super Contributor
timestamp: December 10, 2020, 02:11:12 pm
content: Quote from: vinlove on December 10, 2020, 02:07:37 pmIf you can, loop the coax into one (or more) turn(s) and add the chokes to the loop to keep the loop "in shape", that will work even better

author: cdev
author_rank: Super Contributor
timestamp: December 10, 2020, 03:41:07 pm
content: I have so many of them I was afraid I'd look like aninsane personso I have printed out some excerpts from various published articles that show that indeed, this what people should do, and I put them in my binder in sleeve protectors to show guests if they wonder what they are or why they are all over on SO many wires... So they don't think that I am a nut like those Panawave cultists in Japan or something. I'm just an SWL!Its really striking how much they help, though. I still could use more.Quote from: vinlove on December 10, 2020, 02:07:37 pm

author: A.Z.
author_rank: Super Contributor
timestamp: December 10, 2020, 03:53:02 pm
content: Quote from: cdev on December 10, 2020, 03:41:07 pmYou aren't alone, mind me; but always remember that, while snap-on chokes may/will help, their efficiency is minimal if you compare them to some well built Guanella chokes, just check out the CMC resistance a good Guanella offers and then compare it to the snap-on chokes and you'll see it by yourselfjust in casehttp://karinya.net/g3txq/chokes/

author: vinlove
author_rank: Frequent Contributor
timestamp: December 10, 2020, 04:04:27 pm
content: yeah, I knew that they might work, and tried before. But they were not very effective in the past. Because maybe I just put one ferrite choke for a power lead?This time I put about 3-4 of them on each, and they are wow, working great.Yeah, you need more than one for a device, and they get more effective. More the merrier as they say.I have ordered another 2x packs for coming antenna DIY projects.

author: A.Z.
author_rank: Super Contributor
timestamp: December 10, 2020, 04:29:04 pm
content: Quote from: vinlove on December 10, 2020, 04:04:27 pmFor HF bands, in general, my rule is to use them in groups of (at least) six, placed tightly together on the coax and locked using tape; a good general approach is to place the groups near the antenna feedpoint (say 1m from it), at one half of the feeding coax, and near the receiver input (again 1m from it); but again, this is just a "general" approach, as I said, those won't suffice if you want to really tame CM noise; if you have a toroid around, try winding this oneover the coax, for details, seehttps://www.dj0ip.de/rf-cmc-chokes/different-kinds-of-chokes/d2-guanella-choke/that alone will work "ten times better" than the snap-on ferrites, not that they are bad, keep them (better belt and suspenders), but a good Guanella choke like that one will work MUCH betterAlso, a trick dating back a LOT of time is using a dip-meter to check the coax feedline, and place the chokes at the spots where the radiation is at "max", that will increase the effect of the snap-on chokes

author: vinlove
author_rank: Frequent Contributor
timestamp: December 10, 2020, 04:41:22 pm
content: Wow, that is truly neat stuff. Love it.Yeah, that is the way to do it. I learned it now.

author: cdev
author_rank: Super Contributor
timestamp: December 10, 2020, 05:05:56 pm
content: http://audiosystemsgroup.comis the website of Jim Brown who has written up a wealth of material on the use of ferrite CM chokes and important things like what kinds of materials quell what frequencies under what conditions, also the link sent in the other thread from Altium brings up the point that ferrites can if used the wrong way can make things worse.The energy doesn't just go away, if there is the option, it moves to some other path.ferrites can make quite decent RF transformers of all kinds. Baluns sometime can solve some noise problems very very well. There are a lot of different kinds of baluns.I am just beginning to learn about this, in a more than superficial way. If you're into radio, its one of the more useful things to dig into, I think.

author: vinlove
author_rank: Frequent Contributor
timestamp: December 12, 2020, 08:46:59 pm
content: Hum on the HF when using MLA30 active loop has gone now after fitting the ferrite choke filters.But hum on the Medium Wave when using the longwire in the garden (about 20 meter long) with ATU, is still very bad.On HF it seems a little better. Longwire antenna seems have had always been associated with noisy reception from RFI and hums in general.The ferrite choke filters seem not very effective on the longwire RFI and hum problems.Would there be possible solutions for dealing with the RFI and Hum problems when using longwire and MW bands?

author: cdev
author_rank: Super Contributor
timestamp: December 13, 2020, 12:46:34 am
content: You may need to use a different mix of ferrites for lower frequencies. #31 is better for low HF than #43 for example.I have some blue Arnold cores that are much better than the usual mixes for very low frequencies and you know, knowing what I know now its really time to apply some of the techniques in the first picture in the 18 page PDF to these blue cores, who knows. I might luck out. You can never be too rich or have too many ferrite cores aroundMore turns may not be good if the interturn capacitance is too high.The audiosystemsgroup web site has quite a bit on the use of ferrites to address RFI issue also.I have collected tons of stuff on this subject and it really is useful to know. Experimenting is a good use of time because you can usually make noise a lot better by trying different things to see what works and then trying to improve on that when you have more.If you ever see quantities of useful looking magnetics really cheap, get them!

author: vinlove
author_rank: Frequent Contributor
timestamp: December 13, 2020, 12:00:55 pm
content: Great info and advice, thank you. The articles are excellent read.Will do reading up on them and keep experimenting.I was also thinking of making a simple 9:1 or 4:1 balun with a ferrite ring, and enamel wire, andinsert it between the longwire and ATU.The longwire seem working OK on MW, but very noisy on HF. When the TV is on at night, the longwire is saturated with hum and noise, so unusable.After midnight when the TV is off, the longwire becomes noise free again, and seems working OK on MW. HF is better with the MLA30.

author: A.Z.
author_rank: Super Contributor
timestamp: December 13, 2020, 12:07:32 pm
content: assuming you are using the longwire for rx only, a pretty good balun for your longwire may be the nooelechttps://www.nooelec.com/store/balun-one-nine.htmlhttps://www.nooelec.com/store/balun-one-nine-v2-barebones.htmlnotice that the main difference between the v1 and v2 is the lack of the tap on the v2add a guanella choke after the balun and you'll be up and running, also... ensure to give a good counterpoise system to the long/random wire, that will help, although those aren't "quiet" antennas

author: vinlove
author_rank: Frequent Contributor
timestamp: December 13, 2020, 04:36:56 pm
content: Yes, I use the longwire for RX only.I have ordered the noolec 9:1 balun about 2 weeks ago, and it still has not arrived.It has been shipped from China or Hong Kong or Taiwan somewhere in that part of the world, andwill take another week or two I suppose.But meanwhile I made up a balun or transformer like this onehttp://www.i1wqrlinkradio.com/category/proj/ewe.htmland it seems improved the RX a lot already.I also added a 1/4 wave counterpoise wire to the lw, and it even made more quiet. But MW band still suffers from the TV noise.Some freq. are worse than others.

author: A.Z.
author_rank: Super Contributor
timestamp: December 13, 2020, 07:53:18 pm
content: look herehttps://www.eevblog.com/forum/rf-microwave/putting-up-a-random-wire-antenna/

author: vinlove
author_rank: Frequent Contributor
timestamp: December 13, 2020, 09:43:01 pm
content: That's great info thread for the topic. Thanks.Yes, adding the counterpoise and DIY balun to the longwire improved the noise problem and reception quality on HF noticeably.On MW band? It still is very noisy.I will do more reading on the thread and try to pick out any ideas that will work on MW band noise and hum.

author: A.Z.
author_rank: Super Contributor
timestamp: December 14, 2020, 08:52:37 am
content: Quote from: vinlove on December 13, 2020, 09:43:01 pmA longwire, being an unbalanced antenna, is much more prone to noise than (say) a dipole, also since if it doesn't have a proper counterpoise and/or ground and if the feedline isn't properly choked, the latter (the feedline) will act as part of the antenna and pick up tons of noise. My suggestion is to try using a better counterpoise system (e.g. adding some radials spread around on ground and/or connecting the counterpoise wire to a ground stake) and adding more chokes at different spots along the feedline (notice that a single snap-on choke will do VERY LITTLE, you'll need at least 10 of them in a tight group at each choking point), plus, ensure that your receiver is properly grounded, and with that I'm not referring to the powerline ground, but to a separate good/decent ground connection

author: cdev
author_rank: Super Contributor
timestamp: December 15, 2020, 03:49:32 am
content: You could likely vastly improve your 9:1 unun, using your existing toroid just by winding it differently. The way its wound there is all wrong, at least U'll have much better results using a trifilar winding *for receive any insulated wire will do fine. Cut three wires the same length, lightly twist them Clear speaker wire works well. also insulated enameled wire. Ive usually used #43 core material. If its just for receiving a single#43-50 core has worked well. you could try two cores on top of one another with a bit more wire, that would make a unun you could use for low power transmitting.Or a "sleeve" which originated in a junk fax machine that I have it makes a great #43 magnetic for a small hot" 9:1 unun. Has about twice asmuch ferrite in the same space.Quote from: vinlove on December 13, 2020, 04:36:56 pm

author: vinlove
author_rank: Frequent Contributor
timestamp: December 15, 2020, 10:06:15 am
content: Great info Thank you cdev.Will try that winding method, and make another balun. My order of Nooelec 9:1 small balun still hadn't show up in the post. My DIYed balun is made of very small ferrite ring, about 1 inch diameter. I could only wind about 20 turns for the ant. connection coil, and about 8 turns for the RX, so maybe the transforming ratio is only about 3:1 which is not ideal. Maybe have to buy a large ferrite ring for making about 40+ turns for the antenna? They seem about 12 - 20 quid on eBay. This ebay and amazon buying, which I try to avoid never seem stop with this hobby. The stuff in my junk box is too limited - tons of rubbish but not many useful items. But from the PDF article with 3 wire turning methods, even smaller ferrite ring seem can do the job. Only thing is that it is mentioning for HF coverage. I am now more on MW band RXing these days.I am planning to make this type MW aerial which I saw in youtube. I have ordered a 7m fibre glass pole and it is on its way.With the new sunspot cycle 25, I expected the HF condition will improve, but it seem getting worse. Haven't heard anything interesting lately on HF.So moving towards to MW DXing lately.The youtube presenter is using 3x of the verticals and phase them with some device. But I am just going to make 1x of the vertical, and use it as is, and gradually increase to phasing antenna system in the future. Not sure if it would work at all, but will try. Since I have MLA30 and 20m longwire, a vertical will be another antenna for the MW Dxing.

author: A.Z.
author_rank: Super Contributor
timestamp: December 15, 2020, 10:23:33 am
content: Quote from: cdev on December 15, 2020, 03:49:32 amHi "cdev", yes, you're right, missed that; as for the UnUn, the better performing design I tested was this onehttps://vk6ysf.com/unun_9-1_v2.htmand to make it "perfect", add this chokehttps://vk6ysf.com/balun_guanella_current_1-1.htmto the output of the UnUn (both will be hosted inside the same box), the result will be a good wideband unun and, thanks to the choke, a very good CM noise rejection, then by the way, the longwire will need a good counterpoise and/or grounding system, then by the way adding more chokes along the wire and grounding the coax at the point where it enters the shack would be a good idea too

author: A.Z.
author_rank: Super Contributor
timestamp: December 15, 2020, 10:30:25 am
content: Quote from: vinlove on December 13, 2020, 04:36:56 pmUh... China ? Are you sure you ordered a NooElec balun and not a cheap chinese clone ? Because, see, the latter are totalcrap!QuoteA quarter wave... at what frequency ? Because, see, at MW frequencies 1/4 wave would be pretty longand I also wonder how long is your longwire antenna and how high it's placedAn alternative which could serve you pretty well for lower frequencies (from the 20m ham band, down to LW) and which is very easy to lay out is the "Loop on Ground" antenna designed by Matt Roberts (KK5JY)http://www.kk5jy.net/LoG/the balun is very easy to build and cheap (just a vanilla FairRite binocular core and some enameled copper wire)

author: vinlove
author_rank: Frequent Contributor
timestamp: December 15, 2020, 11:33:07 am
content: Yes, I thought they were the same, but clearly not. They looked similar, but I ordered the cheapest thinking they are the same.https://www.amazon.co.uk/gp/product/B07M7VV9XQ/ref=ppx_yo_dt_b_asin_title_o04_s00?ie=UTF8&psc=1But it was only for about £7, so not big risk, if it is crap.But recently what I found out was, that Made in China products are actually quite OK, and cheap so they are good value for money.Maybe 20 years ago, they were poor quality, but now? They make most of the products used in the whole world.Even big famous named products have the factories in China, and being made in China?It is really the case, even when you think about the Radios like Tecsun and XHDATA and Sangean.20 year ago, many people would have thought they are just toys, because made in China.But now? - most people who are SWLs love these brands, they sell like hot cake.So, I don't know. I am not too worried about it.For 1/4 length is just the length of wire 1/4 length to my longwire 20m long, so the counterpoise of 1/4 is 5m long.It is just a random wire and SWL MIZUHO ATU. Obviously it is not ideal for MW DXing, and I am trying to put out more antennas.

author: A.Z.
author_rank: Super Contributor
timestamp: December 15, 2020, 11:49:25 am
content: Quote from: vinlove on December 15, 2020, 11:33:07 amA clone... and, from direct experience (bought one just for curiosity), it's totalcrap, the frequency response is totally screwedQuoteyou wrote "1/4 wave", making the counterpoise 1/4 of the length of the antenna makes very little sense; you'd probably get better results using a shorter wire connected to a metal stake hammered into ground

author: vinlove
author_rank: Frequent Contributor
timestamp: December 15, 2020, 12:27:46 pm
content: ok, wii try it for a few days anyway. If it is useless, then throw it out, and make a DIY balun based on the PDF.My radio room is upstairs in 2nd floor, so it is difficult to bury stakes or wire into the ground earth, and bring in the wire to the ATU. If it were, then the ground connection wire will become about 1/4 length of the main wire anyway.I am going to make a 7m vertical for MW band, and put it out in the garden soon.It will have earth spike hammered into the ground then, and feed with a 50 ohms coax via the balun.

author: A.Z.
author_rank: Super Contributor
timestamp: December 15, 2020, 12:49:51 pm
content: wait a minute, you wrote that you built a balun for your antenna, but now you're saying that your antenna wire is getting straight into your shack... please explain how your wire antenna is connected, since it's unclear

author: vinlove
author_rank: Frequent Contributor
timestamp: December 15, 2020, 01:14:31 pm
content: It is a simple configuration.20m longwire => Balun on the desk => via 50 ohm coax => Radioor20m longwire => Balun on the desk => Mizuho ATU and 1/4 counterpoise => Radio

author: A.Z.
author_rank: Super Contributor
timestamp: December 15, 2020, 01:15:51 pm
content: it would be better running a coax outside to the balun connected to the antenna and gnd

author: cdev
author_rank: Super Contributor
timestamp: December 15, 2020, 02:01:59 pm
content: The unun design we're both suggesting (its the same if you look closely) is easy to build using the toroid you have now. (assuming its an HF compatible magnetic, I personally prefer ferrites but some people say an iron core is okay too certainly either are far better than nothing at all )And it benefits greatly from having a ground connection, or second best is a counterpoise, which in my case is not connected to the ground in my house, its a long piece of wire that's simply sitting on the ground outdoors and currently not connected to anything of substance, and a pipe thats also not connected to anything else. Just experiment. Anything conductive, the bigger the better, except a rusty object.If you're still not getting rid of the TV's noise, why don't you try adding more chokes there and maybe using a different material that absorbs more at lower frequencies.Also, you can make a great 9:1 unun out of one or two ferrite split beads, (or a two holed binocular core, as that's what we're making here) that works as well or often better than the usual toroid (the doughnut or bagel-shaped magnetic). Just take the three twisted wires and loop them through the single or better yet two slit beads a few times, (keeping them close together and aligned like a pair of binoculars) I would start out with just three loops around the inside of the two split beads - (or maybe even two for higher frequencies) and see how that works for HF and for MF I would try four or five. See what the effect of the different number of turns is. (This is one area where a nanovna and some resistors would be very helpful in figuring out the optimal number of turns.) If you use the toroid you have now, use the same number of turns as in the colored graphic "Balun_9_1" (9) I've been using a tiny FT50-43 core unun that is made exactly like that out of enameled wire soldered directly to two alligator clips and a female SMA for years, Ive also made a bunch and given them away for friends to use with slightly modded RTLSDRs Ive given them. it works like a charm. Attaching the ground to some semi-grounded thing, (in my case a hot water radiator) in my own experience, not the power ground, helps a lot. And then the wire goes out or up as far as you can get it into open space (and as away from the usual e-junk as you can). No need to wait on some package that may never arrive make one yourself out of one or even better, two of your ferrite beads literally in five minutes that should work as well or even better.

author: vinlove
author_rank: Frequent Contributor
timestamp: December 15, 2020, 02:21:01 pm
content: The 9:1 balun I ordered was just for an add-on item while I was ordering other stuff.It was a lot cheaper than the ones I have seen before, so clicked away to see how they will work, at the time I was dealing with the noise in the RX.But yes, great idea using 3 wires to wind in the ferrite ring. I will try it see how it goes.At the moment, the balun is just sitting on the desk in the room as it is not in the water proof box, and it was really 5 minutes job trying to see if it will make any difference.It did make some improvement, but not to great extent. Still MW band is very noisy especially when the TV is on.Now I am wondering, if using large antennas for RXing MWDXing is not such a good idea because it picks up noise and hum from all the electric appliances in the house and neighbours. It would be different matter, if the radio is in the middle of nowhere on the top of the mountain or in the middle of deep forest or field, yes the large antennas would work without much RFI, and will be impressive DX antenna.But sitting in a residential house street, where every house has 100s of electrical appliances running, I was wondering if it would be asking too much miracle which is noise free reception on MW and HF bands at night.So maybe a small loop such as MLA30 or Wellbrook or even the old AOR LA-390 LA-400 loops, these are tiny small loops of about 20cm diameter. Maybe they will pick less noise due to their small size elements and also tuned for the frequency?At night, listening to MW DXing signals last night, the MLA30 on the window curtain pole was hearing far clearer and better than 20m wire in the garden with the balun and ATU.But I am trying to make something better than MLA30 for MW DXing, and it seems not easy.

author: A.Z.
author_rank: Super Contributor
timestamp: December 15, 2020, 02:43:24 pm
content: Quote from: vinlove on December 15, 2020, 02:21:01 pmIf the toroid core is the right material (which material is it ?) and if wound properly, it will definitely make a differenceQuoteBringing the wire straight inside the shack could have been ok in 1930, but today we have a whole lot of noise from domestic appliances, so bringing the balun outside and possibly keeping the antenna away from the domestic noise will be a good idea; set aside the CM noise for a moment, keep in mind that thewholeantenna wire,includingthe portion coming into the shack ispart of the antenna, this means that the portion running near/inside will pick up a whole bunch of noise, that's why, as of today, it's a better idea using some run of coax (the cheap 75 Ohm sat coax will do) between the shack and the antenna feedpoint and locating the latter as far away as possible (50cm at a minimum, the more the better)QuoteIt isn't the antenna, but the way it's set up, sure, there are antennas (like loops) which are less sensitive to domestic noise, but in general the rule of thumb is trying to keep the antenna as much "in the clear" (up and away) as possible, then by the way, you'll also want to add some good choking to the coax to avoid common mode noise, but that's the somewhat easier partQuoteIf the zone is as you describe, I'd suggest you to give up with your vertical antenna idea, such an antenna will pick up quite a bunch of noise; given that you already have a randomwire and an MLA-30 I'd focus on them and try improving their setup as much as possible before going for some different antenna, otherwise you'd be ferreting around until you'll give up thinking that there isn't a solution; I believe you got enough suggestions to get you started, just... avoid going for "el cheapo" stuff, not that you'll need to sheet out tons of money, but avoid "clones" since in many cases they aren't even worth the (low) price you'll pay for them, sure thereareexceptions, but then they are pretty rareQuoteInstead of "making something better", start by trying toimproveyour existing antennas setup; for example you may move the MLA-30 outside and as far away from the building as possible, same goes for the random wire, use a better UnUn and possibly a good choke and feed it using coax, placing the feedpoint away from the building and trying to keep it as "in the clear" as possible, and also give it a good ground and/or counterpoise system

author: A.Z.
author_rank: Super Contributor
timestamp: December 15, 2020, 02:50:59 pm
content: Quote from: cdev on December 15, 2020, 02:01:59 pmAnother design which is pretty interesting is the one shown on page #2in this PDF, it's a 9:1 UnUn built using ferrite sleeves and with a capacitor to compensate for the winding capacitance, I must admit I didn't build it, but judging from the design it looks okQuoteHe's running both, the antenna wire and the counterpoise one all the wayinsidethe shack, that means that the "inside portion" of the antenna will pick up whatever noise there's around

author: vinlove
author_rank: Frequent Contributor
timestamp: December 15, 2020, 02:52:43 pm
content: A lot to intake and digest and learn here.Great advice and info. Thank you A.Z.

author: A.Z.
author_rank: Super Contributor
timestamp: December 15, 2020, 03:11:34 pm
content: Quote from: vinlove on December 15, 2020, 02:52:43 pmJust a note, when you'll finally get your "chinese balun" (don't call it "NooElec" please, it isn't !), assuming the schematic is the same used in the NooElec model, that iswilling to use it with a random wire, you'll need to use a cutter to cut the trace marked as "R1" which is located on the back of the board; if possible add a jumper there, see, with the "R1" closed the balun will be ok for balanced antennas like, for example, a dipole, while with "R1" open it will be ok for unbalanced ones like a random wire, having a jumper there will allow to easily "switch" the balun to the desired configurationForgot, assuming the schematic and connections are the same used in the (original) NooElec one, looking at the balun from the top of circuit with the connector upside and the two wire clamps downside, willing to connect a random wire (and after cutting R1), the right clamp will go to the ground/counterpoise and the left one to the antenna wire, at least that's how the original NooElec is wired

author: cdev
author_rank: Super Contributor
timestamp: December 15, 2020, 03:22:34 pm
content: I don't know how involved you want to get here, but if you have a monitor thats making a lot of RF noise, and aren't scared by opening it up (with the power removed, of course and taking all ESD precautions. Open it up which usually invlves had manipulation maybe using a plastic splunger or credit cards, pop it out of its shell, and then take some copper tape and improve the shielding by adding tabs of copper tape anywhere you see a gap in the shielding. Better manufacturers likely have used very thin but strong metal tape at intervals to create a low impedance RF path from the pieces of metal shielding around the monitor, also over the LVDS cable and other cables that exit the inside of the monitor to go to controls. however, being time conscious, often there are big gaps. Maybe the workers were under time pressure that day or something, anyway, suppose the back of the internal shielding which holds the "module" or whatever to the electronics package is not what it should be, add some pieces of copper ESD tape anywhere these seems like a gap. You can use an AM-FM radio as a sniffer to see where the gaps are, kinda, sorta. Look at it this way, a monitor while its running is an RF noise generator of the highest order inside that box, any gaps in the shielding will leak broadband RF noise like crazy. Its your job to figure out where they are pouring out and bifurcate those holes with enough conductive tape so it will never fall off, and stops the RF sufficiently. Also, replace any of the existing tape thats not on strong remembering that to work the tape has to hug the back and make contact at its edges. Be especially conscious about safety, don't foolishly put it on in a way where it could pose a shock or fire hazard. Be neat.Make a wide enough shield with the conductive tape, to bridge all gaps and provide enough surface, whether it be capacitive or DC.That matters less than it hugging the TV body contours closely (I'm talking about the potential for any protruding or dangling wires that you don't want acting like little antennas)Holding your small radio or radios, changing the frequency from weak used AM and FM channels (the noisse will block them when its bad) go around the TV's beck and sides again bifurcating gaps and covering up any fenestrations without impeding ventilation holes until the RF noise is either gone or attenuated greatly. Don't stop until its gone.

author: cdev
author_rank: Super Contributor
timestamp: December 15, 2020, 03:37:11 pm
content: Do you know what commercial part they use for their balun? (for example, a part number? (Mini circuits, for example))By the way, the cutting of the trace is what I meant some ways back in this thread when describing "galvanic isolation". My soft rock receiver has its antenna input floating for some reason. Anyway, there is lots of junk on my grounds that cannot be gotten rid of so I float both sides even when using an unbalanced antenna. Thats why I use a counterpoise now instead of a water pipe (although the radiator seems to be okay)-----I think another useful mental model for getting more signal and less noise is the idea of diluting the noise with more signal, i other words, the "more" of your antenna that is away a bit from direct noise sources, the less the internal noise thicket around the houses matters..A really long wire if you can get it up into trees might be good. A really thin but strong wire, loosely strung might break eventually in a wind storm but might last long enough to get some good use out of it.Quote from: A.Z. on December 15, 2020, 03:11:34 pm

author: A.Z.
author_rank: Super Contributor
timestamp: December 15, 2020, 03:42:22 pm
content: The transformers for both the NooElec V1 (in the schematic) and the V2 (which hasn't the tap) are from CoilCraft, the V2 uses a CoilCraft WB9-1, don't remember the one used on the V1 now, but the curves for both transformers can be found hereReturn losshttps://www.nooelec.com/store/downloads/dl/file/id/90/product/319/balun_one_nine_return_loss_comparison_to_70mhz.pngInsertion losshttps://www.nooelec.com/store/downloads/dl/file/id/89/product/319/balun_one_nine_insertion_loss_comparison_to_70mhz.pngthe graphs show the curves for both the V1 and V2 versions, not "super" but not bad, eitherHere are the infos about the WB9-1https://www.coilcraft.com/en-us/products/transformers/wideband-rf-transformers/th/wb_th/wb9-1l/and the one used in the V1 of the BalUn should be thishttps://www.coilcraft.com/en-us/products/transformers/wideband-rf-transformers/smt/wbc/wbc9-1l/HTH[edit #2]Here's the whole range of transformers from CoilCrafthttps://www.coilcraft.com/en-us/products/transformers/wideband-rf-transformers/#/they're pretty good and given the small size may be useful for a number of applications, notice that they also manufacture "cans"https://www.coilcraft.com/en-us/products/rf/tunable-rf-inductors/

author: cdev
author_rank: Super Contributor
timestamp: December 15, 2020, 04:54:19 pm
content: I wish there were more variable RF inductors on the market, that didn't cost an arm and a leg, don't you!Slug tuned inductors are much more affordable than roller inductors, and for receiving setups are probably the best way to go in building a passive preselector.They (meaning a tunable and ideally narrow band pass filter) may help get rid of out of band noise a lot and with most SDR receivers OOB noise is a significant factor often overloading their front ends.A really sharply tuned (High-Q) magnetic loop, even one that's indoors, can sometimes be really great way of receiving stuff you possibly never could receive any other way. Like QRP hams and fishing boats on the other side of the world.A good preselector lets you perform the same magic screening out all but a very narrow band of desired signal: with an antenna.Now that I have some better tools for evaluating filters, and know a lot more than I did in the past, I want to revisit preselectors.Winter seems like the ideal time of year for propagation magic because its quieter.I've never used a variometer, and its my understanding they are not the best variable inductor for this, however, they do look kind of fun.Some of the most innovative variable inductor ideas seem often to be born out of necessity and seem to often be invented by hams trying to get on the lowwww bands. I wish I had bookmarked more of the ones I saw in the past! Also old designs, back when those frequencieswerethe high bands, a very long time ago, might yield some interesting, long forgotten designs?Any of us seeking to do MW BCB DX might luck out looking at the hams work because they really need to optimize antennas and systems that are so much smaller than the wavelengths involved, they likely have some interesting setups to get the most out of what they have got space wise.Quote from: A.Z. on December 15, 2020, 03:42:22 pm

author: vinlove
author_rank: Frequent Contributor
timestamp: December 15, 2020, 05:05:07 pm
content: My wife watches the TV every night, and she doesn't like me touching the TV at all in case I will make it not functional intentionally, so no I cannot open it up for the RFI probing.All I could have done was to add a lots and lots of ferrite chokes to the power lead and also the Satellite antenna lead.It seems improved on the HF RX of my radios since then, but MW is still problem and especially with the longwire.MLA30 is now quite OK. I am planning to put the MLA30 outside in the garden. Now it is in the room very close to the radio.I am hoping the MLA30 will further improve in DX RX capability when it is installed in the garden, although I cannot see itgoing up higher than about 6-7 ft above ground.I have a NooElec AM MW filter, which blocks out the MW signal in HF. It is not that effective. Sometimes I used to get MW breakthroughs in HF even with the NooElec filter inline. So I used to think they are not that good.I will keep reading and experimenting with the antenna situation here, and update with any findings and results. cheers.

author: A.Z.
author_rank: Super Contributor
timestamp: December 15, 2020, 05:07:32 pm
content: Quote from: cdev on December 15, 2020, 04:54:19 pmHeh, don't tell me, in a past they were easily available and pretty cheap, nowadays seems like they're made with platinumQuoteAgreed, the issue with most SDR units is that, by their "wide bandwidth" nature, they don't have real frontend preselectors, this means that they can easily overload and become deaf in presence of nearby "blowtorch" stations; on the other hand, the "wide bandwidth" allows to use them as scanners... but there's a price to pay for thatQuoteIn a past, Ive built quite a number of samples ofthis tuned loop, the tuning isn't as narrow as with a regular capacitor tuned loop, but it's pretty good and helps dealing with off-band "blowtorch" signals, and then, if you read the description, you'll find that it's possible to increase the "Q" by playing with the 4K7 resistor value (the resistor placed across the inputs), also, while the TL592 isn't exactly quiet, the design sets it to very low gain which, together with the fact that the circuit is tuned, helps a lotQuoteSure, an ideal preselector should allow to set the desired band and then to also adjust the desired bandwidth, so that, for example, you may use it "wide open" in some cases or "narrow" in other onesQuoteAlso since, in spring/summer I prefer fiddling with antennasAs for roller inductors, have a look at the "roller coils" section herehttp://www.ur4ll.net/they're pretty affordable and could allow to build a good preselector and/or ATU

author: A.Z.
author_rank: Super Contributor
timestamp: December 15, 2020, 05:12:05 pm
content: Quote from: vinlove on December 15, 2020, 05:05:07 pmYou'll need them on the RX too, mind meQuoteSure, the longwire comes directly INTO your home, so it picks up the noise, move it outside and feed it with a run of coax and it will make a difference, by the way you'll want to add chokes to the coax tooQuoteThe loop doesn't need to be high, 7ft will be just fine; ensure to use decent coax to feed it and also ensure to add chokes to the coax and ground it before it enters your building, a device likethis one(just an example, there are other models with different connectors) will fit, just ensure to connect the ground clamp to a decent ground stack using a short and fat wireQuoteIs it arealNooElec one or just another unnamed chinese clone ?

author: cdev
author_rank: Super Contributor
timestamp: December 15, 2020, 05:17:34 pm
content: Sorry to hear about your SO's obsession with the RFI-producing TV.Maybe more split beads will cure the RFI?There is a free (Windows only, unfortunately) program called RFSIM99, a bit long in the tooth, but very useful and easy to use to design filters, as well as other fairly basic RF structures, that might be useful as such . With a handful of components - (and for HF and below, most parts are suitable for use and layout not very critical, with some notable exceptions like placement of cols so as not to interfere with one another.) Anyway, using RFSIM99 you can make your own filters for pennies, and free yourself of having to buy them. Then you too can have an ever growing pile of RF-related "junk". LOL.

author: vinlove
author_rank: Frequent Contributor
timestamp: December 15, 2020, 05:32:30 pm
content: It is good to know MLA30 will work OK on about 6-7ft above the ground.It will be tied onto the washing drying pole in the garden.I think I will still try a vertical for MW DXing when 7m fibre glass pole arrives.If it didn't work well, then I will take it down and put the Active Mini Whip on it.Yes, the MW AM filter is a genuine real NooElec one I am sure.I am not too good to remember or finding out, what makes they are or where they are made now anymore,because they all seemed to work same way, so tended to go for the cheapest ones.For the RFI TV, yup, it has about 20£ worth of Ferrite choke filters. Made me almost bankrupt

author: cdev
author_rank: Super Contributor
timestamp: December 15, 2020, 05:33:10 pm
content: I've only built two varactor tuned loops but my experience with the MVAM-109 was very positive.Curious what varactors/varicap diodes others have used for HF frequencies?A hula hoop also is a good idea as no need to bend it and it wont attempt to straighten itself out.If only they came in "sensible" yard-friendly colors. Not having children and not wishing to use a hula hoop in its intended fashion (although lord knows I need to) if I want one I may have to order one online. I wonder how they ship it?In a plain brown paper package?Quote from: A.Z. on December 15, 2020, 05:07:32 pm

author: cdev
author_rank: Super Contributor
timestamp: December 15, 2020, 05:41:38 pm
content: Since you're looking for lossyness, and real estate on your TV antenna lead, power cord and receiver RX input coax is still plentiful, why not try to bulk out basically using "any toroids you can find as long as they are cheap as can be" .Also, remember, even if they are dinged up, they still likely work. Maybe you could also get a bunch of old CRT ferrites, they used to be used in TVs and other devices that used CRTs. Likely any business that dealt with them has a big box of them lying around collecting dust, (unless its already gone into a landfill)Its worth asking if any of those repair businesses are near you. Maybe I am living in the past and they are all long gone, but, you never know.

author: A.Z.
author_rank: Super Contributor
timestamp: December 15, 2020, 06:17:35 pm
content: as for the hula hoophttps://www.amazon.com/Liberty-Imports-Together-Detachable-Exercise/dp/B0786QMS9M/ref=mp_s_a_1_15?dchild=1&keywords=hula+hoop&qid=1608056053&sprefix=hula&sr=8-15it comes in a regular amazon box, splitted in sections; that said, if you're going to build that varactor tuned loop, open a thread and I'll give you some hints and mods

author: A.Z.
author_rank: Super Contributor
timestamp: December 16, 2020, 08:21:24 am
content: Quote from: vinlove on December 15, 2020, 05:32:30 pmJust pick a piece of PVC pipe (water ones are stronger) so that you'll be able to raise the loop a bit above the drying poleQuoteIfit's a NooElec then it must have the NooElec stamp on it, if it isn't there then it isn't a NooElecQuoteRemember, you willALSOneed to choke the RX power and feedlines, plus, having your antennas inside lets them pick up radiated noise, so move the antennas outside (at that point you may move some of the chokes used for the TV to the RX/coax)

author: A.Z.
author_rank: Super Contributor
timestamp: December 16, 2020, 02:11:43 pm
content: Quote from: cdev on December 15, 2020, 05:33:10 pmSame here, at least with theWenzel's "loopifier", the design of that preamplified antenna is much smarter than one may realize at a quick look to the schematic; the preamp stage is based on a (cheap) TL592 which could easily be replaced with a number of equivalent ICs, now, the IC isn't exactly a quiet one (on MW/SW at least), but Mr. Wenzel used a pair of tricks, first of all the TL592 is set to low gain (1K resistor between pins #2 and #7), second, the (varactor) tuned front-end avoids that the preamp could get overloaded by some "blowtorch" transmitter nearby, since the tuning cuts them off; the resulting active loop performance is quite impressive (in particular if you have an SDR, tuning the loop and watching at the spectrum is quite "spectacular"), sure, you'll have to retune the loop from time to time, but thanks to the "Q killing resistor" (as Mr. Wenzel calls it), that is the 4k7 one across the TL592 inputs, the "Q" isn't as sharp as it could be (btw nobody forbids one from changing the value of that resistor) ... anyhowIf you're going to build a sample of the "loopifier", here are my suggestions (from previous builds); set aside the "keep terminals/connections short" which is the rule for RF stuff, a problem with the preamp, if built (as I did) with separate preamp and controlbox units, is the fact that the the control cable may (and will) pick up RF and inject it back into the preamp causing a number of issues; to solve it, you'll use a coax for the RF and a CAT-5 (network) cable for the control, with such a cable you'll have four twisted pairs which are more than enough, just ensure to use one wire in each pair for the "hi/low", "tune" and "power" and you'll have no issues, plus, you'll have a spare pair which may be used for... another control; that is, as I wrote, the preamp is set for low gain, but nobody forbids you from adding a variable gain control, to do so, reduce the 1K resistor value and add, in series to it, a LED/LDR pair, at that point the "spare" wire pair will be used to carry the voltage for the LED which will then allow you to also adjust the gain level - which may be useful at timesAs you see, nothing special, but it works pretty well; willing to improve its nulls you may then use a "fatter" loop, but that's optional

author: vinlove
author_rank: Frequent Contributor
timestamp: December 19, 2020, 10:22:29 am
content: The 9:1 balun arrived. It is so tiny. It looks like a balun for SDRs rather than desktop radios.I just put it away in the drawer for later playing about with it.I have been so busy doing other stuff. Had to clear one of the rooms in the house due to daughters coming for the Xmas.The room's wall was in bad state, I had to peel the wall paper and re-plaster all the walls and the ceiling.Will have to paint it too. What a miscalculation. Not good idea near the festive season. I thought it would be a day or two job.It turned out 2 weeks jobNo radio works apart from some listening around at nights. Have a great festive season to you all.

author: A.Z.
author_rank: Super Contributor
timestamp: December 19, 2020, 10:41:54 am
content: Quote from: vinlove on December 19, 2020, 10:22:29 amit is an rx only balun, no need for huge stuff; willing to try it you may place one or more turns of insulated wire around a window frame, connect the ends of the wire to the balun and then a coax between the balun and your rx[edit ]or just use some "red/black" speaker wire, wind two turns around a window frame (hold it with some tape), then at the ends connect the black/red wires from opposite sides and connect the remaining two black/red (from opposite sides again) to the balun, the resulting loop should work decently on MW (at least)

author: g0fvt
author_rank: Newbie
timestamp: December 21, 2020, 07:13:16 pm
content: I have not played with my MLA-30 much yet although it is likely to get modified. Like others I was assuming that much of my high noise level on HF receive was likely to be radiated by the satellite cables (we don't have a terrestrial tv antenna any more). I added the traditional FX1588 toroids to the satellite cable and no difference, I also have a common mode choke on the VDSL phone line. The transmit antenna is an open wire fed doublet I have gone overboard trying to kill common mode current on this and it did help. Eventually the MLA-30 will be mounted away from the house, possibly with the loop replaced by a slightly larger copper one. Being based on a video amplifier IC I think they are somewhat short of dynamic range which can lead to artefacts on other bands when RFI is strong.

author: A.Z.
author_rank: Super Contributor
timestamp: December 22, 2020, 08:08:30 am
content: Quote from: g0fvt on December 21, 2020, 07:13:16 pmI believe that, at least, the bias-tee unit should be modified by excluding the voltage multiplier or replaced with a better one, that alone will lower the amount of noise since that bias-tee is reaally noisyQuoteNot sure if the sat cables are radiating, the VDSL may radiate though; at any rate, it would be possible to run a quick check using an handheld receiver, tune it to an empty frequency where you do receive the noise, then move the receiver along the sat and vdsl cables and check if the noise increases or not; notice that the effectiveness of chokes may not be so high, so you may need more of them, plus, keep in mind that a lot of noise is generated by switching power supplies/chargers, and those are widely used (e..g phone chargers, led lamps...) so another countermeasure may be adding some good powerline filters to the wall plugsQuoteOpenwire hasn't CM issues, but if openwire is going all the way inside the building, then it may be picking up noise; in such a case you may consider terminating the openwire outside and getting inside with a run of coax, you may then place a balun and a choke at the junction between the coax and the openwire (a "Ruthroff" balun followed by a "Guanella", hosted into the same box will do fine in my experience), grounding the coax shield may also be usefulQuoteThe "trick" is setting the MLA-30 attenuator trimmer (inside the bias-tee box) to the minimum (no attenuation) and then lowering the gain trimmer (inside the preamp box), to do so you may tune in to some reference station (say a time signal or another not-so-powerful station) and lower the gain to reduce the noise floor at max while still being able to hear the station; this isn't an accurate adjustment, but the only possible w/o un-potting the preamp, doing that you'll avoid overloading the preamp and, at the same time, you'll minimize the noiseHTHJust in case, in my opinion, the mods for the MLA-30 in order of importance are1. Modify (or replace) the bias-tee excluding the voltage multiplier and feeding the box with 12V2. Add a BCN connector to the preamp box, wind a choke with the existing coax and use a better coax (with chokes) to feed the antenna3. Replace the loop with a "fatter" (and possibly larger) one4. Place the antenna as "in the clear" as possible5. Adjust the gain/attenuation trimmers by setting attenuation to zero and lowering the gain6. Add a transformer between the loop and the preamp input (e.g. 2 turns to loop, 8 to preamp on a #73 binocular core)the above mods will allow to improve that cheap antenna performances, reduce the internal noise and avoid preamp overloading and, given that they're easy/cheap I believe they're worth

author: vinlove
author_rank: Frequent Contributor
timestamp: January 08, 2021, 06:05:01 pm
content: Quote from: A.Z. on December 15, 2020, 11:49:25 amTook out the 9:1 balun and connected the random wire coming in from the garden, and to my RX. Works very well. I am quite surprised. The reception is excellent, quiet and pulled many DX signals which I have never heard on HF tropical bands.For £7, it was a great bargain. Only thing is, it is in bare bone, and will need some sort of casing to protect from cracked by stepping on it or dropping something onto it.

author: vinlove
author_rank: Frequent Contributor
timestamp: January 13, 2021, 10:40:55 am
content: Having been listening to HF bands a few days with the cheap 9:1 balun and wire, I have heard many new DX signals, that no other antennas could hear before especially on LF bands. I am really impressed with performance of the balun, especially taking into account of its low low price.This wire with the 9:1 balun antenna is now my main DXing antenna for LF bands below 7Mhz. Above 7Mhz in most cases MLA30 is working better, although the 9:1 balun and wire does better occasionally. MLA30 is also superior for MW DXing.