[Lowfer] loop performance

[Bill Ashlock]

>The square loop has 200 feet of conductor, while a circular one of the
>same area has only about 177 feet.  So, in free space and with an ideal
>resonating capacitor, I would expect circular Q to be 12.8% higher.

Stewart, that's a good point. It's an interesting compromise, particularly 
with my Medfer loop, to surrender radiation efficiency (based on loop area) 
to gain a higher Q, which also improves radiation efficiency due to lower 
Rac.

>In the real world, perhaps coupling and capacitor losses are roughly equal 
>to
>the conductor loss (do you have any figures on this?)

Oh yah! At Lowfer frequencies the loss in a typical bank of silver mica caps 
is less than 1%. Not true at Medfer frequencies.

>it would still leave about a 6% Q improvement.
>But that's only about a quarter of a dB more ERP; only a fanatic would
>invest the additional effort in construction and support for such a small
>gain :)

Now THAT I can buy! But it's always good to understand the variables because 
they have a way of adding up. Actually, now that you mention marginal 
improvements, I've been running a secret test with my 'W's and 'm's 
indicating the effect of -3db, for well over a week. The first and third 
strokes of these character are at -3db compared to the second and fourth 
strokes.  Hard to see any average difference on a full ARGO screen.

Bill
>
>-----Original Message-----
>From: lowfer-admin@mailman.qth.net [mailto:lowfer-admin@mailman.qth.net]
>On Behalf Of Bill Ashlock
>Sent: Wednesday, January 28, 2004 12:34 AM
>To: lowfer@mailman.qth.net
>Subject: RE: [Lowfer] loop performance
>
> >Have you seen any difference in performance of loops with equal wire
> >length but of varying shape?  Specifically, can you tell a difference
>when
> >your loop is "perfectly" round as opposed to being something closer to a
> >square, with essentially horizontal runs near top, bottom, and/or sides?
>
>Eric, there's not much difference in the performance of 2500sq ft loops of
>
>varying shapes as long as the lower horizontal portion isn't much longer
>than 50 ft. My measurements indicate loops, having the same area, that are
>
>much wider than they are tall have excessive ground losses, but I haven't
>put a number on this loss, yet. I also have a hunch that circular loops
>have
>a higher Q than square loops of the same area but I haven't proven this
>yet
>either ....and textbook articles all say there is no difference. Of course
>
>most authors claim the TX loop has no practical value at LF, so what do I
>know!
>
>Bill
>

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