[RTTY] SO2R Problem

[James C. Hall, MD]

I'm thinking about adding stubs to my SO2R setup. I use the TXBPF filters
and they work great, but I was crawling way up the band on 20M and also
looking at 40M, and I could see myself on the P3 panadapter as I approached
the harmonic. These are monobanders so adding stubs for each band would be a
no-brainer. That should help the situation a bit more.

Does everybody just make their own stubs ? I noticed Array Solutions makes
'em. I do have a VNA I caould use for this but have never done it.

73, Jamie
WB4YDL

-----Original Message-----
From: rtty-bounces at contesting.com [mailto:rtty-bounces at contesting.com] On
Behalf Of Tom Osborne
Sent: Tuesday, February 14, 2012 2:04 PM
To: RTTY
Subject: Re: [RTTY] SO2R Problem


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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