Message	Date	From	Subject
140	2006-09-12 09:16:23	Shawn	RX Switch
I've been messing around with the ARRL Challenge, and have been more or less planning to copy the BITX20 with a few changes (QSK, rebiasing of amps for reduction of parts, addition of CW, etc). The QSK part requires a switch of some sort in the RX line, to preven the large TX signal from getting back into the TX line. I'm not sure if this has enough isolation, and maybe the simulator is lying to me; but I added a cap and got a nice boost in isolation from input to output in the RX case. I haven't tested it, not sure when I could; but figured I'd post it here and maybe somebody can run with it. The file is the "ENG 04-0033 TX-RX Switch with 1N4007.asc" in the files section, for those with LTSPICE. Shawn KB1CKT

I've been messing around with the ARRL Challenge, and have been more or
less planning to copy the BITX20 with a few changes (QSK, rebiasing of
amps for reduction of parts, addition of CW, etc). The QSK part
requires a switch of some sort in the RX line, to preven the large TX
signal from getting back into the TX line.

I'm not sure if this has enough isolation, and maybe the simulator is
lying to me; but I added a cap and got a nice boost in isolation from
input to output in the RX case. I haven't tested it, not sure when I
could; but figured I'd post it here and maybe somebody can run with it.

The file is the "ENG 04-0033 TX-RX Switch with 1N4007.asc" in the files
section, for those with LTSPICE.

Shawn KB1CKT