MLA-30 Magnetic Loop Modifications
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- Опубликовано: 17 сен 2019
- The cheap Magnetic loop comes with an included bias-t power supply and very poor coax that makes it very noisy to use on the hf bands straight out of the box, a few easy mods and a comparison with the wellbrook 1530 LN
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Very informative video. Thanks
Great example of using an RSPduo for antenna comparisons :-)
Thanks for sharing!
I just ordered an MLA30+. It will be better than what I have now, nothing. Money is tight and it will do me OK! (I hope) lol
If you divide the difference in performance by the difference in price, then, well, the value for money argument is won by the MLA, hands-down. The WellGood loop is also worth considering at this (and much higher) price point, and may well be better than the MLA.
Hi, regarding long wave. I've tried the Bias-T on my SDRplay and this massively reduced LW signal strength compared to when I used the Biasing Tee that was supplied with the MLA30. I must admit I have the MLA30+ though, but maybe you can give that a try or try a different supply which delivers ~12V rather than the 4.7V that the SDRplay can only deliver.
Putting a bigger loop on the MLA-30 makes a big difference. My antenna for example receives down to around ~20KHz. Submarine communication DHO38 on 23,4 KHz, the British time signal on 60, the German on 77,5 and a couple more at night and day.
It's basically a homemade YouLoop with 3 m circumference on the MLA-30 amplifier. Still goes up to around 30 MHz.
Page 65 of my old 1970 ARRL Antenna Book defines a "small loop" antenna is one whose total length is short compared to the wavelength received, so even a 3 m diameter loop qualifies as a "small loop" at LW. On the same page, it says that small loops "are widely used at frequencies below the standard broadcast band for direction finding." If small loops are directional, do you have a way of rotating your 3 m diameter loop? I am pleasantly surprised to read that your MLA-30+ amplifier works at LW frequencies. I have read that the MLA-30+ is not very directional at HF frequencies. How directional is your 3 m loop at HF? Thanks!
I just purchased one of these. Doing some planning - PVC, connectors and all - and I see in this video that you mention the Bias-Tee is crap, and that you removed it from the equation. Not having any other SDRs or antennae, but with enough knowledge of the basics of power sources, I'm curious if this is something I should do as well, and if so, how I would replace the tee with something "better?" My plan is to make a much larger loop as I am more interested in MW, tropical bands and 160m hams. I'm a total newbie to MagLoops.
thanks for this video . im running the mla 30 and think for the price its a good antenna
I just got an SDRplay dx model after careful consideration. There's a new MLA30+ that seems to give much better lower freq performance. I bought one of those also. Someone will compare a modded one with the MFJ1886 soon and I think the results will be surprising.
Can this modification help to eliminate 50\60hz line noise?
Tried using an MFJ bias-tee but it doesn't make any difference!
What type of coax did you use ? Also did you still use the tin wire as the main loop or you use coax to connect to the wing nuts as a loop sorry if this is a silly question I'm new 🙂 thanks
I use ultraflex 7 it is my favourite for permanent installations due to its size flexibility and excellent shielding for testing and experimenting i do use wf100 sat cable it is 75ohm but for receive it is very good and cheap, The wire loop is still being used I have ordered a aluminium 1m loop (hula hoop) and sere if that offers any improvement
@@UKAFG Fantastic thanks for the reply. I will buy this MLA-30 and do some experiments with it. hopefully reduce the noise with a 9:1 bauln i think good for a beginner to experiment anyway thanks for the good video and the reply.
Have you tried to replace the loop element of this antenna? This is just a piece of a stainless steel wire and I suspect is not very effective (just looking at its dimensions). I am thinking of replacing it with either 2.5m of LMR400 or a copper tube of similar length. This may help with the noise and sensitivity. What do you think about this idea.
What i was thinking did you try this
@@mplmpl7780 I have added a longer loop made of a solid copper electrical wire. I have tested inside my house and I have not seen a lot of improvement. I want to test with a copper pipe and put it outside.
Signals are quite weak below 10 MHz when using the included 60 cm loop. I made a 6 foot loop with PVC supports and it made an AMAZING difference on the lower frequencies.
When you say the noise floor is lower or higher- how do you know that the difference is not in the actual noise floor but differences in the gain of the 2 different antenna amplifiers? The only true test is to compare signal/noise.
UKAFG Can you explain one thing to a newbie? The loop antennas that I see in RUclips clips all have to be tuned very carefully to the resonant frequency that is being received, by means of a variable capacitor. How does this work when it clearly isn't?
The capacitor tuning with the driving inner smaller loop is for transmitting loops only. This MLA-30 is receive only so no tuning is necessary. From what I understand this powered unit here is amplifying sound and likely some noise filtering but not tuning the frequency as in a transmitting loop.
@@cto511987 no
@@cto511987 Not at all. Passive HF receiving loops are generally tuned with a capacitor, and active receiving loops can also be tuned. The MLA30 is whats called a broadband amplifier that amplifies all HF frequencies at once. A tuned loop will always exhibit less noise and have greater narrowband performance.
@@dayleedwards3521 Thanks for the clarification. Back to the drawing board for me.
Is there a stand-alone bias t that you would recommend? The only ones I found must have gold inside - they cost over $1000.
Don Moore
I'm sure that there will be building kits with improved noise performance. (ie. Bias T boards.)
You could get an MFJ-4117 for $45 but there are cheap bias tee's on Ebay for $4.00!
one question. can this compete with the miniwhip? i have no room for big antennas so i need small antennas and i am struggling to buy a bonito mini-whip or this one. i already have the original miniwhip also..
Hi i have not tested a miniwhip so would be unprofessional to comment without doing a direct comparison
might have to use translation, as i am dutch
Very nice very nice one of these days I’m going to get me an SDR so I can look at all that stuff from everywhere. Going to order me a MLA - 30
Would there be any advantage in using the MLA but with a bigger loop?
A larger 4' loop works slightly better than the little 2' loop it comes with especially on the AM broadcast band.
@@stevec2196
Thank you. MW AM is not my target but HF from 3 Mhz upwards to 30Mhz. I assume that there will be a similar improvement especially in the lower to mid range. up to 14 Mhz?
Thank you for your kind assistance.
@@MauriatOttolink There was some improvement over the whole range even on 27 Mhz. The performance is basically identical to a wire I put up that's about 35' long but the loop can be turned to minimize interference.
@@stevec2196 Great stuff... Thank you.
Also. being a loop it will also be less susceptible to noise. 73
Can I ask what does the coax mod do to the performance of the loop?
John Gulliver Yeah. I guess that he doesn’t want to use adapters anymore
The best MOD is to reduce the loop's resistance to .000001 ohms to marginally increase efficiency in a situation where current is totally dependent on reducing resistance. A silver or gold plated pipe of same diameter may help. Changing the the post amplifier coax connections contributes more noise through dissimilarities of impedance and loss in coax joins, and is discouraged. Changing the electronics is impossible because of the design and caulking and the only other facility is to place the antenna in a noise free zone, a half-wave at lowest listening frequecy above an electronic 4x4 mat.This antenna is not designed for maximum wave capture, but for maximum wallet capture. Go figure.
A tree rat on my roof ate halfway through my coax cable so now I have to replace it. I'm thinking 35 feet of something better than what comes with it. Ideas please.
What type of power supply did you use?
If it was an impulse type, it is not surprising that interference occurred.
Typical USB chargers are not suitable.
You should use a transformer-type power supply - the simplest explanation of it is in the recommendation for the C.Crane Skywave SSB radio;
www.ccrane.com/item/alt_dc_skwv_adt/100109/cc_skywave_ac_adapter
I have such a power charger and confirm that it does not cause RFI on MW & SW bands.
This type of power supply should be used for antenna's bias tee injector, obviously with a higher efficiency and appropriately modified power cord.
Check it out and give us your thoughts.
I AM A BIT CONFUSED by the voltage differences listed on the two white boxes. The smaller box reads 5 volts at the USB input and the loop attachment box reads 12 volts and there is no input! My QUESTION is: Do I have to somehow make two different connections to the antenna system or do I just slam 12 volts into the 5 volt USB port on the small white box? Thanks and take care
The bias T has an inverter inside it that produces 12 volts for the preamp from the 5 volt USB input so you can remove the bias T and connect 12 volts directly to the cable going up to the preamp which removes the noisy inverter from the circuit.
A reasonably fair assessment, though you tend to try and explain the difference when the MLA is better than the Wellbrook. The other way around, you say "as expected" of the W/B. Also, the MLA-30 is beyond its design range below 500kHz, so the comparison is not valid.
The bias T should be directly connected to the antenna box, having a preamp on the receiver side just amplifies any noise that is on the coax.
I believe the pre-amp is built into the larger box where the antenna wires connect and that the bias t box is simply a power inserter box for the pre-amp.