[Lowfer] Loop Coupling Xfmr

[Bill Ashlock]

Mike,

Since you are running with a Vcc of only 14.5v the primarary inductance can 
be lower than 400uh. At 1w RL = (Voutp-p)^2/8 = 24.5 ohms for the effective 
load on the transmitter. You want to have the transformer's primary XL at 
least 5 times this or 122 ohms, right? At 185k that would be 105uh. So if 
the primary measures more than 105uh with 7 turns you are OK.

I think I may have come up with a way to receive and transmit on the same 
loop but still have the final at the base of the loop. If you turn off the 
Vcc supply the signal may just pass through the final transistors in reverse 
with some attenuation. Have some more tricks in mind using a negative bias 
on the coax if this doesn't work. According to Jay he has to attenuate the 
signal off his transformer by ~20db to prevent receiver overload, so there 
is plenty of signal to give up. I'll try this at home and let you know how 
it works.

Bill


>From: "WE0H" <we0h@core.com>
>Yea, I was playing around with the turn's ratio and removed one to try it
>and later realized that the inductance would be way under 400uh now. 
>Whoops.
>I'll fix it tomorrow and will try for 9 turns. It is at 7 turns now. If 9 
>is
>worse, I'll have to do a double pass with the loop wire and double the 
>other
>side as well.


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