Hi Jerry
I also use stubs here. I made 2 for each band. Some of them are 52 ohm and
some 75 ohm.
I made some of mine out of CATV 75 ohm coax that I found at the local
Goodwill store here and they seem to work quite well. There was a roll of
it that must have had 3-400 feet in it and got it for $10. Stubs can be
quite a bit less expensive than filters, but the filters probably work
better.
I run about 300 watts with an old SB-200 and I can get pretty close to the
2nd harmonic before I start getting some interference. 73
Tom W7WHY
When I first tried SO2R I was concerned about high RF levels from the
tx antenna coming back down the rx stn line and zapping the receiver
on the other band(s), so I rigged up a simple RF voltmeter and
actually measured voltages presented to the rx.
A combination of stubs and filters got it down to <50mV on most
bands, a max of 200 mv on only one.
This worked for me with pairs of IC756, 756P3, Elecraft K3, and now
Flexes - I have never had any front end damage from SO2R at 1KW from
Quadras. My antenna separation is typically 100 ft or so.
What is the most I can tolerate? I don't know, but I assume it would
take more than a half volt to punch through the typical SS devices in
the rx front end.
Jerry W4UK
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