"Chuck Olson" wrote in message
news
I've been searching for some hints as to what may be in the resin-encased
amplifier used on the Wellbrook loops without much luck. Their power
demand
of 130 mA at 12 volts is kind of high for any FET diff-amp, PNP level
shift,
into a balanced to unbalance output transformer arrangement. I'm using
that
configuration right now on a tuned loop that only requires 17 mA at 9
volts.
Any ideas or links to useful information?

Thanks,

Chuck, w6pkp

Hi Chuck,

The hi Ic is usually indicative of a CATV device being run in a hi IP3 mode.
The preamp I am using on my 7' shielded loop was originally published by
Burhans and described in the 1985 June Lowdown- using a J310 followed by a
2N3904 and a pair of Mouser audio tranformers both IN and OUT. The URL
appears to have gone away- I can send the schematic if you are interested.

Dale W4OP