[Lowfer] Loop antenna question

[John Hamer]

I guess I'll add my thoughts.

If you have a 1 turn and a 2 turn loop with the same length of wire, the 2
turn loop will have around 1/4th the area, and I assume would have about
1/4th the signal passing through it. But since there are 2 turns, you get
double the output as each loop will have current induced. So, I would think
you would lose about half your signal going from 1 to 2 turns.

For my receive loop, I want to receive as much of the lf band as I can, so
I use a variable capacitor to turn the loop the the frequency I am
interested in. The more inductance you have in your loop, the smaller the
capacitance will have to change to get a large tuning range. So what is
more important in my receiver is that I have enough inductance so I can
tune through the range I want with the tuning capacitors I have available.
Also, Tuning capacitors are generally in the 10 - 400pf range or something
like that, so you really just have to make the loop the correct inductance
to get the range you want.

So, if you had a given length and wanted to know how many turns you should
make a receive loop, I guess you have to figure out how large the loop
needs to be to work acceptably, and then use the rest of it to make more
turns for a higher tuning bandwidth. I read on someone's website that 6'
seems to get you down to the noise floor and has decent signal, so I made
my loop 6' and then kept adding turns until I got the inductance that I
needed for tuning bandwidth.

You will of course have the same issue with transmitting loops, but I
wouldn't think having adjustable transmitting frequency could justify the
loss in signal, so you would probably always want a single turn single
frequency loop and maybe just lower your Q for more bandwidth.

But, after experimenting with a loop transmitting antenna this winter, I
have determined they don't work exactly how I think they work anyways, so
maybe that is all wrong.

Regards,
John Hamer

On Sun, Mar 13, 2022 at 3:04 PM N8OOU <n8oou at meekfarm.us> wrote:

> JB,
>
> Your question got me wondering about the answer. I don't have an EE
> degree, so I can't contribute information based on knowledge or experience.
>
> However, I do have yard space, a 100Ft length of wire, and the balun I
> used the last time I played with a LOG (Loop On Ground) antenna. It took
> just a few minutes this morning to gather those components and put the
> LOG back in operation.
>
> I used my KiwiSDR to get spectrum and waterfall graphs of 0 to 15 Mhz
> using my low noise vertical, a single turn 100 Ft circumference LOG, and
> a 4 turn LOG using the 100Ft wire.
>
> The result: The LNV wins hands down. The single turn makes my Lowfer
> signal stronger than the 4 turn, but the 4 turn makes my local 910, and
> 1450 BCB stronger. Interesting....
>
> I have put the screen captures up on qsl.net/n8oou/.
>
>
> 73   de   N8OOU - Mike Meek
>
> On 3/13/22 08:35, Stan W1LE via Lowfer wrote:
> > Would be an interesting experiment, comparing the 2 configurations
> simultaneously.One minor concern may be the self resonance due to winding
> to winding capacitance.
> > I will be monitoring for other's suggestions.
> > Stan, W1LE    Cape Cod   FNN41sr
> >
> >
> > -----Original Message-----
> > From: John Bruce McCreath <weazle at hurontel.on.ca>
> > To: Discussion of the Lowfer (US, European, & UK) and MedFer bands <
> lowfer at mailman.qth.net>
> > Sent: Sat, Mar 12, 2022 9:54 pm
> > Subject: [Lowfer] Loop antenna question
> >
> >
> > 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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