MLA-30+ (refrain) - Page 1
Forum section: electronics / rf-microwave

author: A.Z.
author_rank: Super Contributor
timestamp: February 25, 2021, 02:28:57 pm
content: Have been fiddling a bit with that "Chinese loop", and have some more infos which may be of help of people using itFirst of all, "as is", the MLA is a decent performer on the BC bands and on the lower HF bands, noise floor isn't as low as it could be, but that's easy to cure, then... I had some mailing with some people I know and which are far more expert than me, and they suggested to replace the antenna loop with 8..10 turns of insulated wire to form a loop of about 60..100cm (a hula hoop used as the former will just be fine), and add a 2:1 transformer between the loop and the preamp; didn't yet try it, but judging from some "spice" simulations a friend was so kind to run, such a modification would allow an almost flat response (from the antenna) ranging from around 100KHz to about 100MHz... which isn't definitely bad; but since I was at the same time fiddling with an horizontal loop (triangular, base 9m, height 50cm, sitting at 9m over ground - yes a squished triangle) and since I wasn't satisfied with it, I decided to try a "Frankenstein style" transplant, so I connected the MLA-30 preamp box to the horizontal loop using a short run of 600 Ohm line I had around; the test of this config is still running, and I'll need to characterize it some more, but at a first look, the configuration seems to be doing fine, so in case someone has one of those around and has some room to put up an horizontal loop (at some height, the horizontal ones NEED it), it may be worth a tryThe attached map shows the spots picked up in 2 hours by the antenna (FT8 on 20m), I use FT8 for coarse characterization, later and on the weekend I'll also test it "in person"

author: A.Z.
author_rank: Super Contributor
timestamp: February 25, 2021, 04:34:57 pm
content: just in case, if someone is interested, below is the 4NEC2 model for the loop I'm using connected to the MLA preampCode:CM simple horizontal deltaloop antennaCE' *** symbolsSY hgt=9 ' height from groundSY arm=4.5 ' arms to feedpointSY dpt=0.50 ' height of triangleSY slp=0.25 ' slope from feedpointSY rad=0.0125 ' wires radiusSY tst=7.050 ' test frequencySY seg=81 ' number of segments for each wire' *** geometry of wires (wireid,segments,x0,y0,z0,x1,y1,z1,radius)' left side of triangleGW 1 seg 0 -dpt hgt -arm 0 hgt+slp rad' right side of triangleGW 2 seg 0 -dpt hgt arm 0 hgt+slp rad' base of triangleGW 3 seg -arm 0 hgt+slp arm 0 hgt+slp rad' *** ground parametersGE -1GN 2 0 0 0 13 0.005' *** wires loadingLD 5 1 0 0 58000000LD 5 2 0 0 58000000LD 5 3 0 0 58000000' *** feedpointEKEX 0 1 1 0 1. 0 0' *** initial frequencyFR 0 0 0 0 tst 0' *** end of modelEN

author: A.Z.
author_rank: Super Contributor
timestamp: March 05, 2021, 09:57:40 am
content: Let me start by saying that I don't like FT8, yet I find it an useful "tool" to evaluate the performances of antennas, in particular since receive sessions may be run in a totally automatic way, which allows to run them for extended intervals of time, that said...Sounds like that horizontal loop, feeding the MLA-30 preamp is working decently well, at least judging from the spot I was able to pick during my latest test, I think that picking up signals from the Neumayer station in Antarctica (DP1POL) isn't bad for a simple, cheap antenna like that

author: A.Z.
author_rank: Super Contributor
timestamp: March 05, 2021, 10:25:57 am
content: And since I'm at it, here are a couple images from the very first installation of that loop; later on I modified the MLA-30 box adding a BNC connector and a choke and feeding it with RG-58 coax, the next modification will be replacing the loop wire (about 18m total) with 3-conductors cable and connect the conductors in series (linear loading) so obtaining an "electrical" length of 54m, the idea is to try improving performances at the lower frequencies, I'll probably start testing that modification with a 4:1 balun (homebuilt dual core guanella) at the feedpoint and later on using the MLA-30 preamp, just to see if the preamp will be needed (I prefer going passive, if possible) oh, and the antenna is almost invisible, which isn't bad

author: vinlove
author_rank: Frequent Contributor
timestamp: March 11, 2021, 01:59:29 pm
content: From my testing, MLA30 high noise comes from the antenna amp itself.Not from the B-T.I tried with various different B-Ts to feed my MLA30+, and the NF hasnot changed that much or noticeable amount.

author: vinlove
author_rank: Frequent Contributor
timestamp: March 11, 2021, 02:01:19 pm
content: Quote from: A.Z. on March 05, 2021, 10:25:57 amDoes MLA30 not overload with what looks like longer elements?

author: A.Z.
author_rank: Super Contributor
timestamp: March 11, 2021, 02:12:06 pm
content: Quote from: vinlove on March 11, 2021, 02:01:19 pmI was worried about it, but it doesn't seem to be the case, also since, amongst other modifications, I adjusted the gain trimmer (inside the preamp box) and lowered the gain; as for the noise, the main source is the original Bias-T, then, to further lower the noise one will need some further modifications; sure it won't be a true LNA, but with a bit of care performances will be decent and the higher noise floor will be noticeable only on some bands ... but I plan to deal with that too

author: vinlove
author_rank: Frequent Contributor
timestamp: March 11, 2021, 08:55:13 pm
content: I have replaced one of my MLA30+ element to a hulahoop sized one, and it overloads on some frequencies. On others OK.No noticeable improvement on any thing with the replacement.As I said, I tried various different B-Ts with the MLA30+, but no much difference in the noise.I have now set up 2x MLA30+, 30m long wire with 9:1 balun and 3x Wellbrook Loops all facing different directions in the garden.They all have weaker and stronger frequencies. But generally the MLA30s are more noisy.The Wellbrooks are working great with less noise, but even they get noisy at times for certain bands.But they always outperform the MLA30s.I was quite surprised to find how quiet and well performing the longwire and 9:1 balun is. Again on some bands and frequencies.Now really time for listening the actual bands.

author: A.Z.
author_rank: Super Contributor
timestamp: March 11, 2021, 09:02:32 pm
content: Quote from: vinlove on March 11, 2021, 08:55:13 pmnice, so now, instead of hijacking or trying to troll, just hush away, goodbye.

author: vinlove
author_rank: Frequent Contributor
timestamp: March 11, 2021, 09:47:42 pm
content: Quote from: A.Z. on March 11, 2021, 09:02:32 pmYou must have a huge chip on your shoulder. Troll? Hijack?I was just trying to give you some wider perspectives on the topic.

author: A.Z.
author_rank: Super Contributor
timestamp: March 12, 2021, 05:01:20 pm
content: ok, in such a case, instead of talking about fried air, please post some pics of your antennas and screenshots showing the waterfall/spectrum of your SDR on the 20m band and on others too if you like (it would take minutes to accomplish), those may be of help

author: vinlove
author_rank: Frequent Contributor
timestamp: March 14, 2021, 03:28:45 pm
content: yeah, when time is available I might do that. But I just feel that it is not really meaningful action of uploading the screen captures waterfalls and etc.Because what it really boils down to is at the end of day, can you hear the weak tough copy DX signals well? Can you make out what they are saying? Not the waterfalls or NF figures. Please never waste your time and others time by testing radios or antennas by copying the strong signals, like some folks do in youtube. They are totally pointless.20 bucks portable radios can copy these signals without any antennas.If you are in Europe, try to copy at least the signals from the other continents such as NA, SA or ASIA or Pacific and low powered signals (under 10kW) on the HF and MW.And please don't bother with FT8 or some digital modes, because they will get through anywhere with any piece of wire as antennas. Try using AM or SSB or CW, the traditional modes for the testing.There had been cases when good NF figures and good signal heights and waterfalls, but no audio or garbage content. But there had been also cases when high NF figures and low signal levels but the audio was actually ok to listen to.There are so many factors involved in this, so I wonder if it would be so clean simple to say, this is it.But of course, I am not saying that your attempt to improve MLA30 is meaningless. All I am saying is, please also consider other factors in this game.

author: A.Z.
author_rank: Super Contributor
timestamp: March 14, 2021, 03:46:15 pm
content: come back when you'll have some real world informations, fried air isn't interesting and it stinks; till now you only produced a lot of chatter and no proof, and while I gave you the benefit of doubt, now it's clear that you're talking about imaginary stuff

author: joeqsmith
author_rank: Super Contributor
timestamp: March 14, 2021, 05:58:41 pm
content: Quote from: A.Z. on March 12, 2021, 05:01:20 pmQuote from: A.Z. on March 14, 2021, 03:46:15 pmI've never heard the phase. I suspect in the USA it would mean something like "you're full of hot air" or that's a bunch of BS, bull or talking shit.Adjective. full of hot air (comparative more full of hot air, superlative most full of hot air) (idiomatic) Talking a lot, especially without saying anything of value or meaning. Did the salesman tell you anything new, or was he just full of hot air?So I Googled it and came up with an Italian restaurant selling ozone a few years ago.https://www.odditycentral.com/foods/italian-restaurant-serves-fried-air.html

author: A.Z.
author_rank: Super Contributor
timestamp: March 14, 2021, 06:49:40 pm
content: fine, now, how does all this relate to that cheap mla-30 preamp modifications ?

author: joeqsmith
author_rank: Super Contributor
timestamp: March 14, 2021, 07:13:30 pm
content: Quote from: A.Z. on March 14, 2021, 06:49:40 pmThat's a very good question. I wasn't sure why you kept using the phase as I saw no relevence and was hoping you would explain in real world terms how it fit in.

author: A.Z.
author_rank: Super Contributor
timestamp: March 14, 2021, 07:53:09 pm
content: the "phase" ? ok, maybe it's the usual language barrier at work, anyway, look at my previous mla30 related discussions and at my posts; compare them and make an educated guess

author: joeqsmith
author_rank: Super Contributor
timestamp: March 14, 2021, 08:04:54 pm
content: Quote from: A.Z. on March 14, 2021, 07:53:09 pmI did and posted it above but it seems like you missed it so I will copy it again for your convenience.Quote from: joeqsmith on March 14, 2021, 05:58:41 pm

author: A.Z.
author_rank: Super Contributor
timestamp: March 14, 2021, 08:28:02 pm
content: I doubt so, I was referring tohttps://www.eevblog.com/forum/rf-microwave/mla-30-active-loop-antenna/

author: joeqsmith
author_rank: Super Contributor
timestamp: March 14, 2021, 09:00:06 pm
content: Quote from: A.Z. on March 14, 2021, 08:28:02 pmIt looks like you had a pretty decent start and your last post was recent. Why start over with the same subject? Or, at least why not reference it in your first post here? Just curious.Quote from: vinlove on December 13, 2020, 12:07:17 pmQuote from: A.Z. on December 13, 2020, 12:45:20 pmI understand many radio hobbyist have damaged their low cost VNAs from what they believe is static. With the low frequencies they typically operate, I wonder why they don't add at least an external clamp. Doesn't seem like it would be too difficult to add some basic protection. In their application, it seems they really only want to measure SWR anyway so a bit of loss is no big deal.

author: A.Z.
author_rank: Super Contributor
timestamp: March 14, 2021, 09:06:08 pm
content: as for the reference, my bad, guilty !as for the remainder, since I was here, I just tried to help (for the lil I can), nothing more, is it a violating rules ?

author: joeqsmith
author_rank: Super Contributor
timestamp: March 14, 2021, 09:15:50 pm
content: Quote from: A.Z. on March 14, 2021, 09:06:08 pmNot that I am aware of. Why do you ask? Is something concerning you?Looking at the schematic member Co6aka posted where they show D1 and D2 diodes on the front end, any idea what they are using? In your pictures above, I wonder if static really poses much of a problem. Have you damaged one of the amplifiers with the antenna mounted as you show?

author: vinlove
author_rank: Frequent Contributor
timestamp: March 14, 2021, 10:55:23 pm
content: From my extensive testing, best improvement for the MLA30s were adding, isolating transformer and adjustable attenuator between the antenna and radio.The MLA30+ became super quiet DX active loops.Something like this in this video. He is using Active Mini Whip, but the same principle with MLA30.

author: A.Z.
author_rank: Super Contributor
timestamp: March 18, 2021, 03:33:20 pm
content: Quote from: joeqsmith on March 14, 2021, 09:15:50 pmno, sorryQuoteNo issues till now, and if it goes "poof" no problem, I initially bought that MLA-30 to help a friend which got one improving it, but then since I was at it, I decided to try modding the thing a bit and, while it isn't the best preamp in this world, with a bit of adjustment and a better loop it seems to be working pretty well; got Antarctica several times now, and then it works fine on HF bands and BC ones too, although, to be honest, I prefer "passive" antennas and the plan, as soon as possible is to put up a linear loaded loop feeding it through a balun and w/o any preamp, I'm really curious to see how it behaves (ran some 4NEC2 simulations, but the "real thing" is usually different)

author: vinlove
author_rank: Frequent Contributor
timestamp: April 10, 2021, 11:10:55 am
content: In my testing and observation on the different Active Loop antennas for many weeks and even a few months now, it is impossible to get constant Noise Floor figures from any of them, because they are affected by time of the day, the band condition, and the location of the antennas (even difference of a foot in height and distance from the surrounding objects), and RFI condition of the antenna proximities in the environment. I am sure the weather on the day affects too.So, it seems pretty meaningless to say, this Active Loop antenna has such and such quietness and noise floor figures( which will be totally different in a few hours or tomorrow). It is far better to say, what stations it was hearing.

author: Co6aka
author_rank: Unknown
timestamp: April 10, 2021, 05:22:14 pm
content: Quote from: vinlove on April 10, 2021, 11:10:55 amYou must have a controlled environment; either a anechoic chamber, or replace the loop element with a discrete R/L/C "simulation" of the loop element's characteristics and then enclose the amp in a RF-tight enclosure. Anything else is an exercise in time wasting.

author: vinlove
author_rank: Frequent Contributor
timestamp: April 10, 2021, 08:22:44 pm
content: Quote from: Co6aka on April 10, 2021, 05:22:14 pmEven if the testings are done strictly controlled way, they are still meaningless and waste of time. Because in real uses of the antennas, no one will have the antennas set up in the controlled way. The antennas will be set up out there somewhere under all the influences of the weather, time of the day, monthly and seasonal changes. But most critically, no one can control the actual propagational condition, which will be affecting the noise level dramatically.And what is more, all the other devices in the chain generate their own noise too = the receivers, the power lines, and the feeders picking up the noise ... blah blah, and they all affect and contribute to the noise level of the final output signal.

author: Co6aka
author_rank: Unknown
timestamp: April 13, 2021, 02:59:50 pm
content: Quote from: vinlove on April 10, 2021, 08:22:44 pm"Real use" isn't what's being tested/analyzed, and is a completely different subject. The basis is the amplifier, and its performance is what's being tested/analyzed. "Real use" is irrelevant; if an amplifier's NF is 3dB then it will be 3dB wherever it's mounted, and the same for its other parameters, intercepts, etc. Professionally, that's why antenna "testingsaredone strictly controlled way" in a anechoic chamber andnotin "real use."Everything else you mentioned, weather, time of the day, monthly and seasonal changes, propagation, QRN, QRM, and so on is relatively irrelevant. Except, that a factor many amplifier designers fail to account for is the temperature range the amplifier will be subjected to; temperature compensation must be included in the design, both circuit and mechanical. (Potting compounds that expand and contract at amounts and rates significantly different from the components/PCB they enclose, for example.)

author: vinlove
author_rank: Frequent Contributor
timestamp: April 13, 2021, 04:25:04 pm
content: Quote from: Co6aka on April 13, 2021, 02:59:50 pmHmmm.. I disagree with you totally.The whole point of the antennas, and testings are for the "REAL" use. No one is designing antennas just to test them? No one will buy antennas for just testing and analysing them? The real point is to use them in real listening the signals.if testing and modifying is not going to improve or help in real use of the antenna, then it is just pointless. You would better putting the time for something else which is more productive?In the beginning, I was not sure. Yes, it might improve and help the real listening by the modifications. But after many weeks of observation, testing with different antennas, they all change under the factors. So it was not really going to make any significant difference.

author: Co6aka
author_rank: Unknown
timestamp: April 15, 2021, 01:08:25 pm
content: Quote from: vinlove on April 13, 2021, 04:25:04 pmActually then, you disagree with the entire industry.To test a parameter it must be isolated from others and the effects of others, and then other parameters are introduced to test for interactions.Quote from: vinlove on April 13, 2021, 04:25:04 pmIn the audiophile world you have the same subjective analyses because what matters isn't what's real but what's believed. If what you believe makes you "happy" then of course be happy. Meanwhile though, it's still what it is because it ain't something else.Blessed are those who believe without having seen the measurements.

author: vinlove
author_rank: Frequent Contributor
timestamp: April 15, 2021, 01:51:35 pm
content: double post (Deleted)

author: vinlove
author_rank: Frequent Contributor
timestamp: April 15, 2021, 01:52:24 pm
content: I agree with the tests must be carried out in strictly controlled environment and ways.And I do trust and believe in the measurements from the testings and interpretations and conclusions from it too.What I did not agree was that, the modification of MLA30 and MLA30+ power supply will make the antenna quieter, and therefore better performing.Even the best active loops with super high quality PSUs and parts and all, sometimes got noisy and poor sounding depending on the condition, and the way it is setup, where it is set up, and kind of radios it was connected to etc etc. Too many factors have implication influencing the performance antennas, so I was thinking that any modifications on the PSU of MLA30 would not greatly improve or sound any better than it is from the factory spec.And unless I was to write scientific paper submitting to some institution, I did not need going through any measurements or screen captures of my observations and testings. Just a video which demonstrates which antenna sounds better for receiving DX signal and explanation would be enough.I was just updating my conclusion as promised from the earlier posts in the thread.