MLA-30 Loop antenna

[Matt285]

Has anyone else received their new MLA-30 loop? I have to wait until mid Jan. Please post any reviews or findings. Thanks

[JimIO]

I had mine for a couple of weeks. Nothing to report due to crappy weather.
Next Tuesday: Mostly sunny, with a high near 45. Calm wind. Maybe after then.

~

[chanito]

This configuration works remarkably well, and it is directional enough now to kill some local noise that was plaguing reception. Self supporting as well.

[Matt285]

Thanks for the reply. I see you have configured the loop in a non traditional way. Interesting. Let us know what you've come up with there.

[Matt285]

After hitting submit I realized you did speak about the configuration. Is that the wire that came with it, broken into two smaller loops or did you add new wire? Thanks

[chanito]

It's the wire that came with it, and it is still in one piece, just rolled into two turns then spread out.

[Josh]

I recall reading in the teardown/review that the input of the guts is looking for something on the order of 100 ohms, so a loop that had that z at hf would likely perform best.

[kris]

 Hi -IZS4 pleasantly asked about experience with MLA30, and I will add my pebble to this construction.
I've created a new life for this antenna! But in turn, maybe I will inspire some of you to act.
I bought it straight from China for 35 USD, not knowing many materials about it yet.
From the beginning I was going to improve it. Here are my comments and experience in cooperation with the SDR-FL-Play receiver:
- 63mm diameter loop (203cm circumference 1mm stainless wire) good for holiday trips.
This is low and the expected low signal level was confirmed by tests.
In the MW range only the strongest stations were received, in the LW range the Polish Radio 225kHz station was not received from a distance of approx. 250km. The useful signal started from the 49m band and was getting better at the higher ones. The loop showed directional properties in the 49m band.
A potentiometer for adjusting the HF gain is available in the junction box. I have not observed any distortion of the receiver in any position. Its setting should be guided by an acceptable increase in the noise level. It is variable in different bands and it is difficult to find a compromise. The second possibility of adjusting the signal level is through the HF attenuator in the power supply module / splitter - it also affects the noise level and it is difficult to find the "golden mean". It may be a coincidence, but adding a linear amplifier about 10dB before the input of the receiver caused that many signals already on MW became readable, and was more difficult obtainable by adjusting the HF gain and attenuator.
- the antenna is quiet compared to Skyloop, however, the directional properties of the loop sometimes allow better readability.
> The signal level and the shift below the working range increases with the diameter of the loop, but practitioners recommend not exceeding the diameter of 150cm.
I made a new loop with a diameter of 155cm using (495cm) PE / AL layered pipe with a diameter of 16mm. You could already receive from the LW band, but the signal level did not satisfy me with Skyloop outside the window.
What will happen when I tune the MLA to resonance? Parallel to the end of the loop, I turned on a variable capacitor around 730pF.
Disappointment - while tuning the loop, on the HF waterfal I observed a several hundred kHz wide resonance mound, raised only to around 3dB. Where is the good Q, sharp resonance and high signal level described in the literature?
The input of the symmetrical amplifier (about 1kOhm) is preceded by HF pass-through filters (about 100 Ohm). This is a clear construction error of mismatching with very low loop wave resistance - unless it is deliberately done to ensure antenna broadband.
I see this as a deterioration in the resonance properties of the loop.
>    I solved this problem by using a coupling loop. I unhooked the MLA from the large loop.
 To the MLA connectors I screwed a 30 cm diameter coupling loop made of AL # 3mm wire and mounted it symmetrically against the capacitor.
   And a miracle happened! The MLA antenna from the donkey turned into a racing horse!   
 It tunes sharply with a peak higher by at least 10dB and 50-100kHz wide, so if you tune your antenna too quickly, you may not notice the tuning moment. The receiver (or maybe the MLA amplifier) ​​usually overdrives in the stag signal batch, which requires tuning the antenna from the max signal (I haven't optimized the HF gain and MLA attenuator settings yet).
The antenna now has a clear resonance of around 2.7 to 12 MHz, but also LW and MW are received satisfactorily.
   To end my long description, I recommend that you don't have garden for a full-size antenna, put a rebuild MLA-30 outside the window and enjoy listening effectively to the whole world!
 P.S. Of course, you can do remote operation of the loop by mechanical or electrical re-tuning and turning.
      The symmetrical MLA amplifier requires about 8V for its optimal operation. The designer made life easier for us by supplying typical 5V voltage through a USB socket in the power distributor near the receiver. From here, a coaxial cable to the loop amplifier already has a voltage of 12V. It is stabilized because in the 4-12V range on the input side the output voltage does not change and it does not affect the level of gain and noise.
     You can confidently reduce the MLA noise level by introducing 12V voltage from a classic power supply to the antenna cable outside the 5 / 12V converter.

[Matt285]

Kris, Thank you so much for your detailed review and advise on the MLA-30. Mine is currently on its way to my house. I will post my findings and modify as needed. Luckily I already ordered an an adapter for my Grundig G3 (Thanks for the link Chanito ) i will have to get a SO239 adapter to use my Icom receiver.

[Matt285]

First plan is to add a BNC connector at the box so that I can use different coax. I also plan to seal the outside box better if I decide to use it in a full time outdoor setting. Looking forward to experimenting with it.  for $43.00 I don't have to much to lose. Even if its just an upgrade for my portable, its money well spent.

[Matt285]

So the MLA-30 arrived this evening. I was able to put it up in a temporary way on a piece of PVC I use for QRP portable ops. It will be hard for most people outside of the southeast to fathom, but Mosquito's were eating me alive. I hooked it up to my Grundig G3. Received several stations from Europe and South America, WWV,CHU etc along with activity on the ham bands. I only got to play with it for 15 mins, but I will say it made the Grundig come to life. Worst case scenario it will be a great antenna for portable ops with the grundig and will also be great when I get an SDR receiver running on the laptop to scan the ham bands when im portable. Sometime this week I will order an SO239 adapter for the Icom and do some more testing. I'll keep you posted. Bottom line so far. $41.00 USD well spent.

[chanito]

Kris' info is interesting to me. Upping the voltage to 8vdc is something I'll attempt. My particular MLA-30 circuit board seems to be completely potted, so adjustment will be challenging. The conversion of the MLA-30 to a magnetic loop config is a cool hack.

[Matt285]

For sure. And if something goes wrong, its not like you blew up a Wellbrook. Look forward to any insights.

[Matt285]

Kris, If possible. Could you post a couple of photos? Thanks

[cj468]

I got one of these over Christmas and had a little play with it, mostly on the ham bands. Generally it seems an improvement over the random length long wire I also have, although sometimes the noise increase with MLA means the longwire gives a clearer signal even if not as strong. Only got the display on the XHData as a signal meter but that and my ears seems to indicate the MLA gives stronger reception.

I'd also be interested in seeing a couple of pictures of Kris's mod, especially if it can be done by an "electronics novice" with basic/minimal soldering skill. A few posts on youtube and other forums suggest replacing the coax, as IZS4 also suggests, so maybe I'll try that too.