Automatic Antenna Tuner for general SWL - Page 1
Forum section: electronics / rf-microwave

author: cemelec
author_rank: Contributor
timestamp: October 16, 2021, 06:54:12 am
content: I have an ICOM IC-7300 which I am currently using for listening to the amateur bands but also general HF listeningIn about 2 weeks I expect to gain my amateur radio foundation license and have been looking to get an automatic antenna tuner for my long wire antenna, for example the mAT-180H or similar.How does this cope (or not cope) with non amateur frequencies, as you can't use the tune function?The mAT-180H has manual L/C up & down buttons, but that seems a bit slow and tedious. I realise that the memory functions wont work either without RF going into the box.Is there an ATU which is more suitable, or should I consider bypassing the ATU when in listening only mode and revert to my receive only ATU, which is very quick and easy to use but has no power handling capability.Thanks

author: radiolistener
author_rank: Super Contributor
timestamp: October 16, 2021, 07:00:50 am
content: ATU is good, but you're needs to place it between antenna and feeder in order to get maximum effect.

author: A.Z.
author_rank: Super Contributor
timestamp: October 16, 2021, 07:12:19 am
content: The mAT 180H is an automatic tuner, the buttons only serve to finely adjust tuning if needed, not to tune ithttps://www.vibroplex.com/contents/en-us/d9173.htmlthat said, antenna matching in RX isn't really that important, so you may bypass the tuner if using the antenna for RX onlyThe point is, how are you going to connect the antenna to your rig ? For a base (not portable) installation I'd advise against bringing the antenna wire all the way to the shack, my suggestion is to hang your longwire as far and high as possible, feed it with an UnUn connected to a good counterpoise and followed by a good choke, then a run of coax all the way to the shackEDIT:for further details. seehttps://www.eevblog.com/forum/rf-microwave/putting-up-a-random-wire-antenna/

author: radiolistener
author_rank: Super Contributor
timestamp: October 16, 2021, 07:41:04 am
content: Quote from: A.Z. on October 16, 2021, 07:12:19 amit is important for a weak stations, but you're needs to use tuner at antenna side. Because RX input is already matched with the feeder, they both have about 50 Ω impedance. But antenna has different impedance, so this is where tuner is needed to pull a weak signal out of noise.In addition, tuner plays a role of pre-selector, which also helps to receive signal in a noisy environment.

author: A.Z.
author_rank: Super Contributor
timestamp: October 16, 2021, 07:56:58 am
content: Quote from: radiolistener on October 16, 2021, 07:41:04 amAgreed on the preselector, other than that...https://kv5r.com/ham-radio/coax-loss-calculator/

author: A.Z.
author_rank: Super Contributor
timestamp: October 16, 2021, 08:34:59 am
content: Wait a second, the 7300 has an embedded antenna tunerhttps://www.icomeurope.com/en/product/ic-7300/why do you want a separate one ?

author: cemelec
author_rank: Contributor
timestamp: October 16, 2021, 09:01:30 am
content: QuoteYes, I know that, but will it cope with the somewhat crappy long wire antenna I initially intend to use until I sort out something decent?Why do some ATU's get sold on the basis that they work directly with 7300's? I'm not new to electronics, even receiver design, but fairly new to transmitting.

author: richard.cs
author_rank: Super Contributor
timestamp: October 16, 2021, 09:27:24 am
content: In the HF bands the antenna and/or it's matching have to be pretty bad before they start to significantly degrade signal to noise ratio unless the receiver has unusually high input noise. This is because there's so much atmospheric noise being received on your antenna that it dominates over receiver input noise, and a poorly matched antenna that gives you weaker signal also gives you less noise. This generally means that you get little or no receive benefit from an ATU.If you have stronglocalnoise sources you start to benefit from an antenna with some directionality, but you can generally get away with a pretty poor antenna for HF receive. This is not the case in the higher bands where the external noise is less and the receiver noise floor dominates.

author: radiolistener
author_rank: Super Contributor
timestamp: October 16, 2021, 09:35:50 am
content: Quote from: richard.cs on October 16, 2021, 09:27:24 amWhen I tune tuner for magnetic loop antenna at short wave, I hear very strong difference between tuned and untuned tuner.The same thing happens with ferrite antenna, there is very strong difference when it is tuned or untuned.The effect of antenna matching for receiver will depends on antenna bandwidth.

author: A.Z.
author_rank: Super Contributor
timestamp: October 16, 2021, 12:33:08 pm
content: Quote from: cemelec on October 16, 2021, 09:01:30 amthere was an old saying about rigs and antennas which sounded like "one for the rig, 99 for the antenna", now, while that's pretty extreme, it's rightSo, my suggestion is to start by setting up your antenna and feedline properly and then decide if you want an external ATU or notSo, I suggest you is to reread my post, and in particular, the link about the "random" wire antennas, set up yours properly and then move on from there; notice that, for listening you may consider the idea of using a separate antenna, for examplehttp://www.kk5jy.net/LoG/http://www.kk5jy.net/rx-loop/in such a case you may consider the idea of investing into an automatic antenna switch, so that you won't transmit by mistake with the rx antenna, at that point you'll be able to add to the rx antenna whatever preselector or LNA you wantBut first of all, set up properly your main rx/tx antennaEDITas for the tuner, it is COMPATIBLE with the 7300 along other Icom rigs, but this does not mean that the 7300 needs it, but I'd better invest some money into some FT240-43 toroids, and some lenght of good coax cable (from direct experience the "Messi & Paoloni" one would be a good pick

author: HB9EVI
author_rank: Frequent Contributor
timestamp: October 16, 2021, 04:50:20 pm
content: in RX the only thing that really matters is the signal to noise ratio; impedance matching is secondary.if you want to use your long wire (how long is it actually?), it makes sense to use an automatic tuner at the feed point; the internal tuner is not very useful;also the matching area of internal tuners normally are in a range of 3:1; specially on the longer bands, you'll have lower impedance than the tuner can handle due to simple fact that even 'long wire ham antennas' are still too short and too low above ground for the wavelenght to reach a higher radiation resistance

author: A.Z.
author_rank: Super Contributor
timestamp: October 16, 2021, 05:02:14 pm
content: The basic idea, when it comes to "random" wire antennas, that is end fed wires which aren't resonant, aren't a 1/2 wave on some band and aren't multples of an 1/2 wave (those are EFHW or longwires), is to choose a non resonant lenght on all the bands of interest so that impedance won't be too low (near a 1/4 wave) or too high (near a 1/2 wave), at that point, using a 9:1 UnUn we bring the impedance down to a value which will allow a reasonable coupling with a coax and then, use an ATU to make our TX happy, that's it.for further details, please seehttps://udel.edu/~mm/ham/randomWire/

author: geggi1
author_rank: Frequent Contributor
timestamp: October 16, 2021, 06:21:19 pm
content: If you are using a long/random wire antenna you should use a a longwire tuner like the Icom AH-3, AH-4 or some other tuner of a similar kind.A long/random wire antenna will have a high impedance feed-point typically in the range of 1000 Ohm or more. These tuners are made for taking the high impedance feed-point impedance down to somewhere close to 50 Ohm giving you a SWR of about 1:1.Some of these long-wire tuners have several hundred memories sometimes over 1000 and will not loose the settings at a power down, either by battery backup or some kind of static memory.Get one tuner (with CI-V) of this kind ang get a local Ham come over to you and tune up your antenna on several spots on each ham band.The tuner will tuner your antenna when you change frequency.

author: A.Z.
author_rank: Super Contributor
timestamp: October 16, 2021, 07:17:22 pm
content: that's ONLY true if you bring the wire straight to the tuner w/o using an UnUn (and choke !) to connect the wire to yor rig, again, been there, done that and knowing what I'm talking aboutEDITwhile nothing forbids it, most examples of end fed antennas show the wire going down (from whatever height) straight to the ATU, now, that works, sure, but it's FAR from an optimal setup; the latter would mean having a REMOTE tuner connected to the wire (and CONTERPOISE, in real life an end fed NEEDS it !)was I saying ? Oh yes, the feedpoint of a random, ok, try using a modeling software and check what. happens when you RAISE the feedpoint and use a good counterpoise, for example, a vèrtical wire, coming down from the feedpoint to ground. and connected to (say) two radials in inverted T config

author: radiolistener
author_rank: Super Contributor
timestamp: October 16, 2021, 08:11:39 pm
content: Using ATU near transceiver is a bad choice, this is not effective way. It leads to a lot of losses in the feeder. Such configuration can be used when adding tuner at antenna feed point is very complicated or even impossible.With integrated ATU or with tuner placed near transceiver you're using significant part of your transceiver power for heating the feeder and ATU, this part of power does not enter the antenna and just lost.And this is why ATU integrated into transceiver in many cases are useless.But there is also compromise option exists, you can put ATU in the middle of feeder. As short as you can to antenna feed point. Such configuration allows to reduce losses in the feeder and improve antenna efficiency. Of course such tuner needs to be automatic, because it will be placed far away from the operator. Usually such a tuner is placed on the roof to be close to antenna.Aslo, ATU integrated into transceiver has a limited tuning range. This is why external tuner still may be required if your antenna with feeder requires very high L or C for matching or if it has very high or very low resistance.Note, that if your antenna is not matched with feeder, impedance on antenna terminals is not the same as impedance of antenna connected through feeder. In such case feeder works as impedance transformer and it's input impedance will depends on feeder length. So, you can't tune your tuner near the transceiver and then move it to antenna side, you will needs to retune it at antenna side.

author: A.Z.
author_rank: Super Contributor
timestamp: October 16, 2021, 09:40:17 pm
content: sigh...https://svarc.us/swr-the-persistent-myth/and I think it's time to stop those myths

author: radiolistener
author_rank: Super Contributor
timestamp: October 16, 2021, 11:41:26 pm
content: Quote from: A.Z. on October 16, 2021, 09:40:17 pmWhat myths you're talking about?Power loss in the feeder is not a myth. This is a property of transmission line and you can find the value of that power loss in the coax cable datasheet.For example here is my measurements for 20 meters of Chinese RG316 which I bought on aliexpress, taken from 1 kHz to 90 MHz (see attachment). It is pretty close to RG316 datasheet specification.As you can see, it has pretty significant loss. And that loss will be multiplied for each time wave travels back and forth through the cable between your ATU and antenna before it will be consumed by antenna. It will happens when you use ATU on transceiver side instead of antenna side.On the contrary, when you use ATU on antenna side, that loss happens just once, because there is no reflected waves in the feeder. And wave travels back and forth between tuner and antenna with no needs to loss something on a long feeder.VSWR cannot show you all details. In order to see details, you're needs to understand what is going on in the feeder, tuner and antenna.This is the typical myth that VSWR at some section can show you total efficiency of your feeder-tuner-antenna system. No, it can't.For example someone can replace your antenna at the end of feeder with 50 Ω dummy load and you will not be able to detect it with SWR meter. It will show you SWR about 1, but it doesn't means that 100 % of power is transferred to your antenna. Because your antenna is completely disconnected and all power is dissipated into heat on a dummy loadIf your tuner allows wide range tuning, you can just disconnect antenna from tuner and tune it to have VSWR about 1 in the cable between transmitter and tuner. But it doesn't means that you transmit all power with 100% efficiency. It didn't transmitted at all and dissipated into heat inside your tuner.This is because your SWR meter connected between transmitter and tuner show you just VSWR in the feeder between transmitter and tuner, but it don't show you VSWR between tuner and antenna. It don't show you losses in the feeder. And it don't show you how much power is radiated by antenna, how much is dissipated into heat in antenna and how much is dissipated into heat by some object in the near field of antenna.Another example, you can connect long enough coax cable with open end to your transmitter and get VSWR=1.0 on SWR meter connected between transmitter and coax cable. Because all power is consumed by coax cable and dissipated into heat.This is why it's better to not focus on the VSWR value, but taking all things into account. Include things which happens in the feeder, tuner and antenna.

author: A.Z.
author_rank: Super Contributor
timestamp: October 17, 2021, 07:52:08 am
content: Quote from: radiolistener on October 16, 2021, 11:41:26 pmI was referring to that paper about the SWR myths I posted, as for RG316, it's ok for short pigtail cables, but using a long run of RG316 to feed an antenna is a very bad idea; for RX only better using RG6, for TX too, go for at least RG8

author: A.Z.
author_rank: Super Contributor
timestamp: October 18, 2021, 09:53:10 am
content: Quote from: cemelec on October 16, 2021, 09:01:30 amThat's your main probleminstead of throwing money into an external ATU, use it to improve your antenna, buy some length of decent coax cable, by or build a 9:1 UnUn and a 1:1 choke and put up your antenna "in the clear", connecting it (and a counterpoise wire !!) to the UnUn + choke and feeding it with coax going all the way to your transceiver, then the trick is cutting your antenna wire so that it will NOT resonate on any ham band so that the internal ATU, with the help of the 9:1 UnUn at the antenna feedpoint, will be able to find a match; to sum it upFind a length in this table which will fit your available spacehttps://udel.edu/~mm/ham/randomWire/for example a 70ft wire will allow you to cover all bands from 80 to 10 meters (if you have more space, pick a longer length from the table, e.g. 85ft) , add another piece of wire with a length of about 1/4 to 1/3 of the antenna length which will be dropped down as the counterpoise, next, build a 9:1 UnUn like the one described herehttp://vk6ysf.com/unun_9-1_v2.htmbut use an FT240-43 toroid core and wind 9 turns, next build a choke like the one described herehttp://vk6ysf.com/balun_guanella_current_1-1.htmuse another FT240-43 core for it, and wind 17 turns using a piece of RG-174 coax, at that point connect the output of the 9:1 UnUn to the input of the choke and host both into a box with a connector for the coax and binding posts and eyelets for the antenna wire and counterpoise, plus an eyelet to suspend the boxall the above will cost you much less than the external ATU and the result will work MUCH better than your current "arranged" antenna connected to an external ATU, it's the antenna which radiates/receives, the ATU won't improve a crappy antenna ! Remember again, invest more in your antenna system (everything from the antenna to the rig) than in other components, without a good antenna even a gazillion dollars rig will have crappy performancesHTHForgot, if you don't want to build your UnUn and Choke but prefer sheeting out money to buy them, you may pick (just an example) thosehttps://palomar-engineers.com/ferrite-application-experts-2/Bullet-50-450-9-1-HF-Unun-1-8-61-MHz-500-Watts-End-Fed-Antennas-p74356620https://palomar-engineers.com/antenna-products/baluns-and-ununs/1-8-30-mhz-balunsununs/11-toroid-baluns/CUBE-Feed-Line-Choke-Unun-5KW-1-8-61-MHz-20-38-dB-Common-Mode-Rejection-Static-Bleeder-Ground-Option-p74536617

author: cemelec
author_rank: Contributor
timestamp: October 18, 2021, 01:55:44 pm
content: A.Z. thank you for your detailed and informative posts, they are very helpful.I'd pretty much decided to go the way you suggest, but one question: Isn't the 1:1 choke supposed to go as near to the transceiver as possible?I have seen that suggested in various places: i.e long wire > 9:1 unun > coax > choke >coax > radioI may or may not wind my own (I've wound small ones for Rx only) but the commercial ones are not too expensive and by the time you get your toroids, boxes, connectors the savings are not huge.I'll try the 7300's own ATU first, and see how it goes. 80m - 10m would be fine for me.My next step might be a collapsible 10m mast, they seem quite interesting, but that's for another day

author: A.Z.
author_rank: Super Contributor
timestamp: October 18, 2021, 02:13:54 pm
content: Quote from: cemelec on October 18, 2021, 01:55:44 pmYou're welcome, just trying to helpQuoteIt may be put near the rig too, but my suggestion if possible, is to place one choke near the antenna and a second one near the transceiver, then adding more chokes will NOT hurtthe point is that, even with a good counterpoise, an endfed antenna will still "try" to use the coax as part of the radiating system, and sincerely, I'd try avoiding that, so, placing the choke near the antenna AND connecting a decent counterpoise will help, then, if you want adding more chokes along the feedline and near the rig, won't hurt; but now that I think at it... didn't you get your license ? Once upon a time that meant passing an exam, and the latter involved some basic stuff. including CM currents... but maybe nowadays things changed and I'm just an old fart ...Quotetwo or three FT240-43, the winding wire (for the UnUn) and RG-174 coax (for the chokes), plus the box and the other stuff won't cost so much, commercial decent/good UnUns and chokes would cost much more, assuming you aren't going to buy CRAPPY chinese stuff which will cause problems instead of solving them, that isand then, willing to go for "buy" (SIGH ... where is the ham spite today ?) the unun and choke from "palomar" (again, NOT promoting them, just. an example) won't cost you more than the ATU, and then connecting the ATU to a poor piece of wire brought directly INSIDE the shack won't offer you the same results of a properly set up antenna, even if it's a humble "random" wireQuoteWith the current antenna, w/o a good setup ? Well, good luck with that ! But remember, the "problem" is not the 7300, it's the ANTENNA and adding an external ATU to the combo will still resuilt in a CRAPPY antenna and a waste of money (to buy the external ATU), again, skip the idea and start by setting up the antenna as needed, that's the ANTENNA which radiates and receives, if it's crap then adding tuners, preamps or linears will just mean wasting money without solving the problemForgot, the antenna is an "end fed" one, but don't call it "long wire"; a long wire antenna is at least one full wavelength long (or multiple of a wavelength), an EFHW is an endfed with a length of 1/2 wave at the lower desired frequency, a "random" is an endfed calculated so that it will NOT be a multiple of 1/2 wave on any of the desired frequencies and that it will be near/above 1/4 wave at the lower desired operating frequency, so please, avoid calling it "long wire", it's a mistake

author: borjam
author_rank: Unknown
timestamp: October 18, 2021, 02:57:11 pm
content: Quote from: radiolistener on October 16, 2021, 09:35:50 amThat's an entirely different question. Loop antennas (and a ferrite antenna is also a loop) are extremely narrow band tuned elements. So, tuned loops are actually a corner case.And unless you tune the loop antenna itself no antenna tunner will correct it after the fact.

author: radiolistener
author_rank: Super Contributor
timestamp: October 18, 2021, 06:38:29 pm
content: Quote from: borjam on October 18, 2021, 02:57:11 pmYou can match it with tuner on receiver side, but high losses in the feeder will make it useless.Shortened magnetic loop antenna needs Q factor about 1000-2000.10 meters RG316 has insertion loss about 1 dB on 14 MHz.As you can see it will be just impossible to get even Q=10 with so high loss per cycle in the cable.This is why the tuner should be placed on antenna side.If your antenna with feeder and tuner works bad for TX, it will also works the same bad for RX.Note that in RX mode your gain is limited with thermal noise on 50 Ω of receiver input, so you cannot use gain to compensate weak signal attenuation due to antenna mismatch.

author: A.Z.
author_rank: Super Contributor
timestamp: October 18, 2021, 07:02:10 pm
content: Quote from: radiolistener on October 18, 2021, 06:38:29 pmand, without quoting the remainder of your post, and aside adding confusion to chaos, what's your suggestion for an antenna setup to be used for both rx and tx ? A tuned loop ?

author: radiolistener
author_rank: Super Contributor
timestamp: October 18, 2021, 07:07:47 pm
content: Quote from: A.Z. on October 18, 2021, 07:02:10 pmI said above - use tuner on antenna side. At feeding point. In order to exclude feeder from matching circuit.Magnetic loop is a bad choice for TX. Due to high Q, magnetic loop has more losses on heating and extreme high field strength near it (which is not safe for your health).

author: A.Z.
author_rank: Super Contributor
timestamp: October 18, 2021, 07:13:18 pm
content: Quote from: radiolistener on October 18, 2021, 07:07:47 pmtotally out of topic

author: radiolistener
author_rank: Super Contributor
timestamp: October 18, 2021, 07:34:41 pm
content: Quote from: A.Z. on October 18, 2021, 07:13:18 pmThis is a subject of topic. Topic starter asked if a tuner can help for RX.Yes, it can, but it needs to be placed at antenna side. Not on receiver side.The internal tuner integrated into transceiver is useless for RX.

author: A.Z.
author_rank: Super Contributor
timestamp: October 18, 2021, 07:40:25 pm
content: just to sum it up; start by setting up a proper installed antenna, given your current set up. skip (at least for the moment) balanced feeders, and put up a decent feeder (coax) with unun and choke, that will cost you less than that "automatic ATU" and, since at the end of the day, it's the antenna the thing which works, the result will be better than the one obtained by wasting money buying an ATU connected to s piece of wirethen. money is yours, so you are free to waste it as you like better, in such a case you may invest into an ATU and use a light bulb as your antenna.

author: radiolistener
author_rank: Super Contributor
timestamp: October 18, 2021, 07:48:32 pm
content: Quote from: A.Z. on October 18, 2021, 07:40:25 pmIt depends on the use case. For example, if you're using a lot of different bands, it may be worth to use remote controlled ATU at antenna side instead of a bunch of dedicated matching circuits for each band with remote control unit to switch between them.

author: A.Z.
author_rank: Super Contributor
timestamp: October 18, 2021, 07:55:10 pm
content: dedicated ... what ?

author: radiolistener
author_rank: Super Contributor
timestamp: October 18, 2021, 08:09:32 pm
content: Quote from: A.Z. on October 18, 2021, 07:55:10 pmmatching circuit for each required frequency band (with fixed tune).

author: richard.cs
author_rank: Super Contributor
timestamp: October 18, 2021, 08:56:36 pm
content: Quote from: radiolistener on October 18, 2021, 06:38:29 pmI mean yes, with an electrically-small, magnetic loop but that is a very extreme case. With many other (nearly all other) antenna types the ratio of reactance to radiation resistance is far less and you end up with a matching circuit with a Q of perhaps 3 to 10. In that case matching at the "wrong" end of the feeder becomes much more acceptable. Yes, the losses are higher than matching at the antenna, and yes you may need a better feed cable to partially-mitigate that, but you have to balance this against the advantages of an indoor matching arrangement. i.e. accessible for manual tuning, not needing to be weatherproofed, etc.Combine with the fact that forlisteningin the HF bands specifically you can throw away many dB of signal and not care. Seehttps://upload.wikimedia.org/wikipedia/commons/9/93/Atmosphericnoise.PNG- at 14 MHz you can waste 20 dB in a bad feeder and/or with a mismatched antenna and not significantly affect your signal to noise ratio provided your receiver front end noise is modest. Agreed you can't get away with something like a magnetic loop without tuning, but a random wire of significant length doesn't need tuning for receive. A fixed 9:1 in impedance as others have suggested will get close enough, and if you loose 10 dB of received signal it doesn't matter because you've also lost 10 dB of received noise and you're still safely clear of your receiver noise floor.Transmit is another issue entirely. You care about losses more because generating much more RF than you need is a pain, but it's still not absolute. You can still choose to trade a few dB of losses (generate a few dB more RF) for some other engineering gain such as easier maintenance by putting the matching the wrong end.

author: borjam
author_rank: Unknown
timestamp: October 19, 2021, 05:58:33 am
content: Quote from: A.Z. on October 18, 2021, 07:02:10 pmI have a MFJ 1788 loop and it is excellent. Loops are not as inefficient as models predict and it is quite simple to prove it. Where does the energy go? I have been transmitting with mine and a thermal camera doesn't show any heating at all.For SWL they are cumbersome because you would need to be retuning whenever you change the frequency. But there is a plus to it as it helps reject off frequency interference which might cause problems for receivers with a poor front-end.And there are also receive only broadband loops like the Wellbrooks. The received signal level is lower than, say, a dipole, but the signal to noise ratio is significantly better.

author: borjam
author_rank: Unknown
timestamp: October 19, 2021, 06:03:22 am
content: Quote from: radiolistener on October 18, 2021, 06:38:29 pmWhich was my point.It is important to understand the difference betweenadapting the impedance of an antenna to a feederand actuallytuning an antenna. The term "antenna tuner" is not especially accurate.Imagine you have a Yagi for, say, 7 MHz. You can make it work for 10 MHz by changing the length of its elements (and their spacing) which would mean you aretuning the antenna. Or you can match it to your coax using a "tuner". Will the result be equivalent? Not at all. Energy will be wasted as heat unless you really tune the antenna itself.

author: borjam
author_rank: Unknown
timestamp: October 19, 2021, 06:08:40 am
content: Quote from: radiolistener on October 18, 2021, 07:34:41 pmAny impedance mismatch will induce losses. So, obviously, a proper match between antenna and feeder will improve reception.However, bear in mind thatthe reason why SWR is kept low for transmission is, in the first place,to protect the transmitter circuit from reflected energy. A SWR of 3:1 means a power loss of about 25% which, in dB, is almost negligible. But the transmitter may have a really hard time to cope with that and the protection circuits will reduce power further. Or some final stages can just break.So, imagine you have a a SWL antenna with a SWR of, say, 6.0:1. The loss is 50%, which means 3 dB. Is 3 dB such a dramatic loss? Given the HF band noise it's not a deal breaker.

author: A.Z.
author_rank: Super Contributor
timestamp: October 19, 2021, 02:59:53 pm
content: Quote from: cemelec on October 16, 2021, 06:54:12 amTrying to sum it up, skip the idea of the external ATU and use the 7300 built-in oneSet up the antenna as shown in this image (no artwork!)keep the ropes between the antenna and the two supports long enough to allow for a spacing of 50cm to 1m (or more), the antenna wire doesn't need to be horizontal, it may be sloping; use a pulley at the far end support and connect that end of the support rope to a weight (it may even be a brick) so that, if the antenna is loaded by wind or ice, the rope will be free to slide and the antenna wire won't break, that's a very old trick, but it still works; optionally you may add a second pulley to the other side of the antenna, that would allow you to lower the whole antenna for manteinance if/when needed, lay the counterpoise down as shown, the counterpoise wire may also be laid down on ground if needed, for the ropes pick some good UV and weather resistant one, the so called "paracord" may fitAt the "near" end of the antenna connect a 9:1 UnUn, following it, connect an 1:1 choke, either directly after the UnUn or just before the coax enters the building, the coax will then go to an ATU or, if your rig has an embedded ATU, directly to the rig, use decent quality coax (I suggest using RG8 at least) and good connectors, stay far away from "chinese" UnUns, Chokes and coax cable, they usually suck !As for the length of the main antenna wire (the horizontal one in the pic), select it from herehttps://udel.edu/~mm/ham/randomWire/picking the longer length which will fit your available space (70ft is the minumum to cover 80-10, 135ft is the minimum for 160-10), try keeping the antenna in a straight line, if possible; if not you may run the wire at some angle (at/above 100°) either/both horizontally and/or vertically.whatever you'll decide, please, PLEASE, do NOT use that piece of wire you are calling "longwire" to transmit... and then say bad words at that poor IC7300

author: radiolistener
author_rank: Super Contributor
timestamp: October 20, 2021, 11:21:57 am
content: Quote from: A.Z. on October 19, 2021, 02:59:53 pmYour setup is okay, but I would suggest to avoid unbalanced antenna and use classic dipole with center feed point. It helps to reduce interference from home equipment. RF choke can reduce it for unbalanced antenna, but don't eliminate.

author: A.Z.
author_rank: Super Contributor
timestamp: October 20, 2021, 07:34:31 pm
content: forgot, "cemelek", if you're still here, after the chaos and noise someone tried to generate, please keep us up to date about your antenna setup for TX and RX

author: cdev
author_rank: Super Contributor
timestamp: October 21, 2021, 01:36:21 am
content: There is no such thing. Knobs work fine for receive preselectors or antenna matching. Since it doiesn't transmit.You can use an unun and an untuned wire of a number of different random, nonreasonant lengths to get the SWR low enough so you dont need a tuner. (this works with a 9:1 unun and a 43 foot wire. (posted before reading the whole post, I am basically suggesting what AZ suggested here. If you avoid the resonant lengths you avoid the impedance extremes its hard to tune out with a transmatch..You can tune the SWR significantly lower with a Z-match, of S-match (which both are fairly easy to make. Z-match can tune most unbalanced loads. S-match is particularly good for balanced antennae.. even loops.. (it is itself a sort of loop electrically, which is why I like it) Radiolistener would I suspect likely like it with his dipole.. )Quote from: cemelec on October 16, 2021, 06:54:12 amI dont understend, do you mean for receive? You would do fne with a Unun, which decouples your antenna and improves reception across the bands.. Get one of the new NanoVNAs and build your own collection of tuners. Thats a lot of fun. Another fun tuner thats good for receive because its got a sharp peak, it has a high Q is an S-match which is especially good for balanced antennas. It -like the Z-match also has a modest parts count. If you are working QRP it can be built for almost nothing. You can get toroids from mini-kits.

author: A.Z.
author_rank: Super Contributor
timestamp: October 21, 2021, 06:52:00 am
content: Quote from: cdev on October 21, 2021, 01:36:21 amThat was exactly my point, the OP (cemelec) wrote he owns an IC7300 and will have his license in some time, he also stated he has a "piece of wire" he has been using for RX only (with his 7300, I suppose) and asked how to use that "piece of wire" as an antenna, now, given that he seems to want go for an endfed, I suggested him to put up a random wire antenna but do so "the right way" since plugging that piece of wire to the center of the coax connector and trying to transmit with the 7300 won't be exactly a good ideaQuote from: cdev on October 21, 2021, 01:36:21 aman endfed isn't exactly a balanced antennaand the IC7300 has an embedded matching unit, so if the endfed is properly setup (as I described in a previous post), the tuner of the 7300 should be able to deal with it; that said, for an endfed I'd probably go for an "L" match (not willing to start a debate about antenna matching units, mind me !), that one in my experience (if properly built) can match quite a good range of impedances and has lower losses than other matching networks, a coarse example of such a circuit can be seen in the attached image

author: cemelec
author_rank: Contributor
timestamp: October 21, 2021, 02:07:59 pm
content: Again thanks everyone, and to A.Z. for his inputI came across this:INRAD RX7300 RXhttps://www.nevadaradio.co.uk/product/inrad-rx7300/Basically on the IC-7300 it switches between a receive antenna and a transmit antenna.As I'm interested in non amateur bands as well, I could use the cheap (no power handling) manual antenna matching unit I already have on a separate less demanding antenna than my future Tx antenna.Just a thought

author: A.Z.
author_rank: Super Contributor
timestamp: October 21, 2021, 03:02:19 pm
content: Quote from: cemelec on October 21, 2021, 02:07:59 pmThe mod is nice, sure, but I believe that before thinking to two separate antennas you'd better improve your current antenna since that will improve its receiving performance too, then you may consider the modification and, in turn, consider which rx only antenna will fit/match your requirements. But again, start by setting up your "main" antenna correctly.To be even more clear, your current setup with the wire going all the way inside the house and to the receiver isn't good neither for receiving nor for transmitting, you're bringing part of the antenna inside, this means that in reception it will pick up all the noise from the house appliances (switching PSUs, plasma TVs and then more), while in transmission it will also radiate INSIDE which will cause a number of problems.So, start by installing your antenna properly (and I already described that), then once you'll have that fixed you may consider ways to improve the setup, but doing that now and pretending that buying some "magic" piece of stuff will turn your piece of wire into a good antenna will just result in a waste of time and money

author: cdev
author_rank: Super Contributor
timestamp: October 23, 2021, 06:21:13 pm
content: Quote from: A.Z. on October 21, 2021, 03:02:19 pmI'm going to try to illustrate this with some hopefully helpful photos that makes what I suspect you might be able to use and build cheap, now, clearer..The second photo is of an elecraft commercial it thats easyto replicate and very useful to have.. the schematic is identical to the image * TwoInOne-balun-toroid-version.jpg The switch is super useful and the balun works all the way up through six meters just like the IC7300.These switchable balus are super useful indoors and generally when you have several choices (switchable) the one with the loudest signl is likely to also be giving you the lowest SWR. Then the rigs tuner will get you the rest of the way, we hope. I would use low power, whenever there was any doubt. RF power transistors are expensive, often.Its amazing the useful things you can make out of what my wife sometimes calls "junk"To make a 9:1 un-un (to match a single long wire antenna close enough in SWR to 50 ohms to be tuned by an in-rig tuner.. you just need some (two) big old cheap ferrite material beads, two.. and a few feet of twisted wire, enough to run a triple stand of wire through the two beads maybe a dozen times. Treat it like a binocular core. This will give you the electrical equivalent of a 9:1 balun wrapped on a toroid binocular core.. very easy to build if you like me possess LOTS of split beads. Select two identical ones to make your "binocular core" mimic a commercial binocular core..Emulate the winding of the classic 9:1 unun. Again make sure you ground the part you are supposed to ground. You could use two more split beads top help isolate your feedline. At its ends. But that is not necessary IF it is grounded properly. It just may make a bit of a reduction in that noise picked up on the last bit of the feed line.These are some "interesting" (to me) HF impedance transformations, that I thought might have wide appeal. One of these (airbaluns.gif) can be constructed without any magnetic cores at all (but it probably works better made with two of the "Ukrainian" ferrite rods from ebay or other magnetics. (You can make almost anything out of those split bead cores in a pinch).This was made by Pa0fri , its fromhis site on the S-match. (balanced antenna tuner) It has a sharp peak so its useful for HF receive more so than baluns, generally. It will match your antenna and also preselect. Very helpful for use with RTLSDR/upconverter combinations. (high vulnerability to out of band interference, so preselection is more important than with a more selective receiver. )

author: A.Z.
author_rank: Super Contributor
timestamp: October 23, 2021, 06:31:15 pm
content: Cdev ... my name is Andrew, in case you wonder, then I totally agree, FIRST set up the WHOLE antenna system and THEN reason about ways to improve it