MLA-30+ Mag Loop Antenna

MLA-30+ Mag Loop Antenna - Redeemed?

Рет қаралды 6,733

Жыл бұрын

With an S-9+ receive noise floor on the full length dipole antenna, is the mag loop antenna able to redeem itself?
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April 2024 Notes - Is this a “mag loop” antenna?
In response to a couple of viewers who stated, “This is not a mag loop antenna”…
I did some research on this… it would seem you are correct, but… Hahaha! As always, with so many things, “it depends” comes into play.
On page 9.13 of the 2023 (25th edition) ARRL Antenna Book, I found a little box with a statement about the definition of a Mag Loop antenna. It references the Mar/Apr 2020 QEX technical note which defines the boundary as being where the circumference of the loop is less than .05 wavelength. This is where the electric to magnetic field ratio tips in favour of the magnetic field.
In this case, a 1 meter diameter loop is considered a mag loop at frequencies below 4.8 MHz… so on 80 meters, this would be considered a “mag loop”. At 40 meters and above, it clearly does not meet the definition.
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VE6WGM (VE6WO)

Пікірлер: 24

@StratmanII 9 ай бұрын

Very informative video. Probably not many people know this, but there are counterfeit versions of the MLA-30+ sold online. My first "MLA-30+" turned out to be a fake copy, the wire loop was impossible to form a reasonably perfect circle and its bias tee was noisy. The seller used pictures of the genuine Megaloop but sent me a counterfeit set instead. My second purchase was all good; I got it from a different seller on eBay and asked him all kinds of questions. I probably irked him a bit, as he had been selling only genuine Megaloop antennas and he knew about the fake ones. True to his word, he shipped me the original MLA-30+. The difference between a genuine MLA-30+ and a counterfeit one is like night and day. I've seen at least two other videos on YT whose authors assumed that they had the genuine MLA-30+, therefore their comparisons with their existing EFHW antennas (or whatever they were using) were very flawed. The fake one comes with a Bias Tee box with a very high noise floor and is fitted with either a dim red or blue colored LED indicator (the original bias tee comes with a bright green LED) and the LNA box has only four screw holes instead of six. In all the review videos in which a genuine MLA-30+ was used, the low noise amp box is always screwed into the PVC pipe using the middle screw hole and the reception results were quite satisfactory. If the reviewer had to fasten the LNA box to the PVC pole with zip ties it meant that he received a fake one, which lacked the middle hole. Hope this helps anyone who is considering buying the MLA-30+ online. 🙂

@xxcrazy_critr6661 8 ай бұрын

Hmm. I purchased one of these 6 months ago, and still haven't used it, as I use a Homebrew Version that I believe has a much lower noise level because the Differential Amp chip that is used in the MLA-30 antennas is a cheap POS, my Homebrew design uses a pair of very low noise transistors for the differential amp. Probably cost more than the MLA-30 chip being used, but well worth the reduction in Noise. Anyway. The one I have has a BRIGHT (annoyingly bright) GREEN LED in the Bias Tee box, and the Differential Amplifier Box (not an LNA!) has 6 screw holes, one of which on top and bottom are in the center. Is that supposed to be the Genuine version? I think you said in your comment that the fake one has 6 holes and real one has 4, but then you said in the review videos where the box is mounted with the center holes, the RX is good, contradicting what you said. No offense intended, just trying to get this straight on the one I have before I attempt to use it or modify it or throw it in the trash.

@xxcrazy_critr6661 8 ай бұрын

Ah about the contradiction my bad. Not enough coffee yet this morning, I see you said the Blue or Red LED in the Bias box = counterfeit MLA-30 and 4 screw holes in the Differential Amplifier Box = Counterfeit. So mine is assumed to be the REAL version, however VE6WGM appears to be using the assumed Counterfeit MLA-30.... Needs to do a follow up video taking it all apart and lets see the difference in the Guts. By now he should be able to find a REAL MLA-30+ to buy and compare both to put the Counterfeit thing to rest. I see potential for KZbin Views, so hopefully he will do it.

@ve6wo 8 ай бұрын

I have tried the MLA-30+ that I have here a few more times after this video, and each time was disappointed with the performance. It works, but the signal to noise ratio is not as good as my inverted vee dipole. I am able to use the directivity of the loop to place the noise source in the null, but it doesn’t turn into an advantage because of the poor s/n ratio. I will investigate the difference between what I have and a “real” MLA-30+ antenna… I have also purchased a yagi for VHF/UHF to use with my FT-857D running on a battery pack to try to locate the noise source/s around my QTH. I have some work to do… will likely post another follow up video on this when I get some time. I work full time out in camp in northern canada, so, it’s a time thing.

@xxcrazy_critr6661 8 ай бұрын

@@ve6wo I use an Active Loop that I made myself with better parts. Old design from 80's. It is very low noise compared to my wire antennas here in the City. I use it for my WebSDR Server. I purchased the MLA-30+ just to do comparisons between it and my Homebrew just haven't gotten around to doing it yet. I use the directivity of the Active Loop to minimize or completley null out the noise from the Cable TV lines here in the City that run above ground on the Utility Poles. Without that I cannot copy much on 80M and below, full of switching transistor noise and it's associated harmonics. Key to Active Receive Loop performance, this is a Differential Amplifier, not a traditional LNA, the key is to use a loop material that is as low inductance as possible, as the differential amplifier sensitivity depends on low inductance. The skinny wire loop with the MLA-30 is probably the worst thing you can use. A piece of copper tubing or flat bar, or even braided coax would be a better choice for the actual Loop material than the skinny wire, as it's inductance is likely a bit higher vs a larger surface area.

@xxcrazy_critr6661 8 ай бұрын

@@ve6wo Oh and for locating noise sources, I generally just walk around with a portable (9V battery powered type) AM radio and listen to the noise, it's source is usually a lower frequency like between 80-180kHz switching power supply or other consumer junk, and the associated harmonics are what we hear in the HF bands. I also use a laptop and SDR receiver tuned to LF-HF band to help locate the frequency of the noise source and calculate it's harmonics, so I know for sure it's not more than one thing making the noise.

@raulgongora5288 3 ай бұрын

Twaskyou sr very interesting. Blessings

@theodoresears4369 7 ай бұрын

Ground the common noise on both antennas. Coaxail lighting arrestor. Also 8 foot ground in clay or earth to your coax.

@kensejkora4424 8 ай бұрын

Hi Gregg. Another great video. You demonstrate well how one can use a loop to null out noise. One point worth noting is that at about 04:56 you seem to experience the highest noise levels. However, that is the point at which you move the loop closest to the laptop, so it is likely some of the increased noise may be due to picking up noise from the laptop itself, most likely the display screen. The best test would be to locate the loop at least 10 feet from the laptop, with the loop and support post oriented vertically, and turning the support post to rotate the loop through the vertical plane. Keep up the good work and good DXing. 73 Ken -- WBØOCV

@g0fvt 6 ай бұрын

My MLA-30 redeemed itself too, recently bought another HF rig with dual receivers so with headphones you can listen in "stereo" with two antennas, one on each receiver. Sometimes the more readable signal is from the MLA-30, my noise levels are often very high on 40m, both with a 1/4 wave vertical and low dipoles. The MLA-30 is going to get some attention, probably a slightly larger loop and a decent mounting further from the house, they don't measure well for dynamic range but a great basis for some experimentation. FWIW I had already reduced my noise levels substantially with the combination of a current balun in the HF feeder to the main antenna and common mode choking of the electricity supply to the entire shack. 73

@petergore1972 2 ай бұрын

Peter Gore Seer, I Have AMLA-30, On A Trio,R-2000, Its North To South, With The Magnetic Poles, Its Working Good And My RF Switch Works At Its Best With Antenna.

@xlr8also Жыл бұрын

A mag loop and some very good common mode chokes from My Antennas saved my operating for about a year. I was able to pin point the noise using the 30 db notch in the loop. While listening to my receiver in the shack over an FM radio transmitter I turned the loop just right and killed the noise. I'm presently using the MLA-30+ in the attic for SWL and found placing 3 turns of the coax thru a small snap on ferrite helps just before the preamp.

@ve6wo Жыл бұрын

Very good! I will try this :-)

@AdamosDad 3 ай бұрын

When the loop is horizontal, it becomes an omni-antenna with little Near vertical incidence skywave.

@fullsoundrecording 8 ай бұрын

this is not a mag loop folks

@ve6wo 3 ай бұрын

I did some research on this… it would seem you are correct… but…. Hahaha! As always, with so many things, “it depends” comes into play. On page 9.13 of the 2023 (25th edition) ARRL Antenna Book, I found a little box with a statement about the definition of a Mag Loop antenna. It references the Mar/Apr 2020 QEX technical note which defines the boundary as being where the circumference of the loop is less than .05 wavelength. This is where the electric to magnetic field ratio tips in favour of the magnetic field. In this case, a 1 meter diameter loop is considered a mag loop at frequencies below 4.8 MHz… so on 80 meters, this would be considered a “mag loop”. At 40 meters and above, it clearly does not meet the definition.