I use RG11 75 Ohm coax here for everything - feed lines, stubs -
everything. Like you, I got a sweet deal on a BIG batch way back when...
I remember finding a lot of good info on the internet when I needed
to make and tune my stubs.
My stubs:
Used independently:
Pass 80, null 40+20+15+10 This on the 80 meter port of radio A
Pass 20+10, null 40+15 this on the 20+10 meter port of radio A
Combined on the 40+15 meter port of radio B:
Pass 40+20+15+10, null 80
Pass 40+15, null 20+10
Not much SO2R anymore, but if necessary I could operate two adjacent
bands SO2R.
Jerry W4UK
At 03:03 PM 2/14/2012, Tom Osborne wrote:
>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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