Gary,
many thanks for the quick reply and your precious info, particularly
appreciated the details on the transformer inside your commercial version
AYL-4 of the loop, which are not publicized on the web site
http://www.aytechnologies.com/Products/products.htm
>
> Toroid transformers work well, but the windings require a lot of care to
> get maximum performance. The original K9AY Loop (1996) is the last time I
> used a toroid for an RX antenna -- winding a conventional
> primary/secondary transformer on a binocular core is much simpler, and has
> equal performance.
>
> My K9AY Loop and 9:1 Beverage transformers are "binocular" using two large
> 77 material beads (Amidon FB77-6301) with separate windings of #22 AWG
> wire -- 3 turns for the 50 ohm side and 9 turns for the 450 ohm side. The
> measured loss is around 0.2 dB from below 160M to at least 20M. This
> material and winding scheme works well at lower frequencies, too, since
> many loop users are Broadcast and low frequency DXers.
>
I have a couple of binocular BN73-202 left (I wish I had ordered more to
Amidon) and there should be not a great difference with material 77 you use:
from Fair-Rate tables I see 2.500 mu of permeability at 1 MHz of the 73 vs.
2.000 mu of the 77 stuff at the same frequency.
I wound 3 turns for the 50 ohm side and 8 turns for the antenna side:
with a load of 395 ohms I get 48 ohms - SWR = 1.02
with a load of 470 ohms I get 55 ohms - SWR = 1.05
on the AEA CIA analyzer, so this would be my choice.
BTW: these are the termination values that I am going to switch on the K9AY
loop, as I have enough wires in the control cable.
Thanks again Gary and best 73
Luis IV3PRK
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