Magnetic Loop Antenna Questions, Please

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BOBRR

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Hi Folks.

Saw a brief writeup on the YouLoop Passive Magnetic Loop Antenna by the AirSpy folksthat
recently became available. Cheap enough at only about $ 30.

Am very weak on antenna theory, along with an "old age" problem, so let me please ask you experts out there.

I do only receiving, up to about 30 MHz. No transmitting.

Presently use a 30 foot simple long wire outside.
Leaves a lot to be desired.
Due to space restrictions, would be hard to make longer.

a. For anyone actually using, any opinions as to whether this antenna might be worth trying ?

What is the diameter of the loop ?

b. Is it "directional", in that I would always have to orient it to the station location I want to receive ?

If so, Is it "very" directional ?
Most sensitive in the plane of the loop, or at 90 degrees to it ?

c. Does it become "omni" if the plane of the loop is placed horizontal ?

Would appreciate any thoughts on.
Pros and cons, limitations, etc.

Thanks,
Bob
 

prcguy

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A shielded passive loop is a little less sensitive than a non shielded passive loop of the same size. I have a small single turn shielded loop around 12" dia commercially made for RF/EMI testing (Empire LP-105) and its quite numb but does work and the noise floor is super quiet. But some weak signals are just not there. I use this loop mostly for HF and interference direction finding.

I also have a home made shielded loop about 1m in diameter where the loop of RG-11 coax has the shield severed at the top, the grounds tied together via a metal box at the bottom and the two center conductors feed a wide band 4:1 balun. That works noticeably better than the smaller commercial loop but still way down from my W6LVP active loop and it misses a lot of stuff that a long wire type antenna picks up.

Both loops have a very good and sharp null in the direction looking through hole of the loop but its very narrow and you could probably rotate the loop for best overall reception and park it there never needing to turn it. I do this with my W6LVP active loop where I can receive signals from N-S and E-W and I parked it where the null doesn't seem to affect anything I want to hear. The null is still there and I can rotate the antenna to make use of it if needed. I've never tried this type of loop horizontal to see if its omni directional but I will try at some point.

I've tried a few 50 ohm in and out preamps on my passive loops and they don't come close to the performance of my W6LVP active loop. My preamps are really high end, overload proof but they peak out at around 15dB gain where the internal preamp in the W6LVP seems to be a lot more. I also think there is an advantage to matching a preamp directly to the loop impedance instead of matching the loop to a 50 ohm preamp with a transformer or balun.
 

mbott

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I purchased the YouLoop but I haven't had the opportunity to get it out in the wild for a proper evaluation. I did try it inside just for grins and the results were less than impressive. I had better results with the whip antenna of my Eton/Grundig Executive Satellit than I did with the YouLoop connected to my Airspy HF+. I am going to wait until I can get it outside before I make a final judgement.

--
Mike
 

vagrant

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I expect the whip on your Eton would work better than that loop. Still, I believe the loop would null out noise better. Give WWV a whirl indoors and outside on their various frequencies. A simple comparison between the built-in whip and the Youloop is fine...presuming you have an adapter and your Eton particular has an antenna port.
 

mbott

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I purchased the loop for outdoor use for when the opportunity arrises to get away from the suburban "noise" that plagues the home QTH. My primary antenna at home is the Pixel RF Pro-1B which I do have on a rotor for just the reason you point out above. It is very effective. For the last year or so, I've been using the Wellbrook ALA1530LNP as my getaway antenna as it can be powered by 8 AA batteries. It works great, but I'm looking for something more easily transported. With that in mind, I'll wait until the weather (and Wuhan Virus) cooperates for the next "test" of the YouLoop.

--
Mike
 

vagrant

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I received a Youloop from Airspy this week and I am pleased with the results, considering the size of the antenna. Indoors provided plenty of noise and the loop directivity helped to some degree. Outdoor use dropped the noise floor significantly, no surprise, and I was impressed with the receive on lower frequencies. I initially use WWV and CHU frequencies for testing, then move on to other always weak or always strong SW broadcast stations.

Overall, I found it suitable for casual SWL fun with the quick setup/take down of its compact design. I should note that I did not try MW and lower yet.

I also tested with a passive tuner inline (Miracle Ducker IL) which improved RX versus without it, as well as 1.8 ~ 30 MHz bandpass filter (BPF-1432). Still, even without those I was pleased with the results, keeping the overall size in mind.
 
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