[RTTY] SO2R Problem

[Tom Osborne]

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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