[Lowfer] Loop antenna question

[Steve Ratzlaff]

I too wondered about this, and did my own experiment just now. I had a 
20' piece of 1/2" aluminum fuel line tubing already as a single-turn 
loop, and used that. It measures 6.43 uH at 100 kHz (DE-5000 LCR 
meter).  I thought I'd use my weakest daytime beacon as a check (251 SV, 
NM). I wound a 10:22 turn matching transformer to approximately match to 
50 ohms at 251 kHz.  But even with a 11 dB Norton amp the signal was 
down at the noise floor and not usable. So I switched to 25.2 kHz which 
is a strong signal here in Southern Arizona keeping the transformer's 
turns ratio and the Norton preamp.  The 20' circumference is about a 6.4 
foot diameter loop; I pointed it toward North Dakota for peak signal. I 
used the Perseus SDR, 100 Hz CW bandwidth, Slow AGC and measured about 
-95.5 dBm.

I took the loop down, measured 10 feet in and put tape there, then made 
a rough two-turn loop with rough 10 foot circumference per turn, with 
about 5-6 inch spacing between the turns and put that up. It measured 
7.11 uH which I figured was close enough to the previous one-turn loop's 
inductance to use the same matching transformer as before. I used the 
same Norton preamp. This time the signal measured -108 dBm with the same 
Perseus CW 100 Hz bandwidth. So quite a bit lower signal compared to the 
one-turn loop, at 25.2 kHz.

Take this data for what it's worth to you, perhaps at least interesting 
anecdotal results--but it does appear to go along with J.B.'s 
comments.    :)

73,

Steve AA7U in AZ (south of Tucson)

On 3/12/2022 7:54 PM, John Bruce McCreath wrote:
> For a given length of wire, would a single turn loop pick up more signal than
> a multiple turn loop?  The single turn loop would have a larger capture area,
> so it should produce better results than if the same length of wire was used
> in a multi-turn loop.  However, there may be other factors that I’m not aware
> of, so I’m asking for your comments and suggestions.
>
> 73, J.B., VE3EAR
>
> LowFER Beacon "EAR"
> 188.831 kHz. QRSS30
> EN93dr
>
>
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