That shorted stub cut for 20m has to be installed on the 20m station
(station B) to suppress 40 and 15 there.
On the 40m station (station A)you will need an open stub cut for 20m to
suppress 20 and 10m interference.
Both stubs will be around 23 feet long when made from RG213,
73
Peter
-----Original Message-----
From: CQ-Contest [mailto:cq-contest-bounces@contesting.com] On Behalf Of
Mike Smith VE9AA
Sent: Dienstag, 8. September 2015 23:14
To: towertalk@contesting.com; cq-contest@contesting.com
Subject: Re: [CQ-Contest] Coax Stubs for SO2R
Thanks for the many replies so far. So today after I got home from work I
tried just running radio A @ about 1w on 7.000MHZ and saw S9 on 20m and s1
on 10m.
No change switching stub in or out, so I took Jim's(K9YC) suggestion and
moved the stub farther away from the transceiver. I made up 3 random length
patch cables and so have the stub roughly either:
10-12', 15'-17, 20'-22, 25'-27 away from the transmitter (Radio A). (rough
guesstimates) ( a 1/4wl, accounting for VF would be in the 23'-27' range)
No perceptible change whatsoever at any point in the line no matter where I
put the stub. Just the slightest SWR change when I put it in line. Almost
cannot detect it.
I am going nuts.
It's either something in the shack or something outside rectifying (I
guess?) but these are pretty low power levels. (usually 100w, but also at
1w !)
Radio A (transmitter in the scenario) is hooked to an amp (not turned on in
close to a year), an antenna switch, a tuner/wattmeter (used on
straightthrough function only, just for it's wattmeter/SWR function.)
Radio B (receiver in this scenario) is hooked to its own power supply and
coax straight outside to a multiband dipole some 100' from the Radio's A's
various antennas. No SWR meters, switches or anything.
They share a 4" hole in the wall in the garage where they exit to the
outside, where the RG8 or LMR400 coax;'s could be close to one another.
They share 120VAC in the shack (but different power supplies)
I have two additional (perhaps important?) questions. Should any of these
harmonics between any bands sound pure and "clean", like a real CW signal?
Mine all sound low/muffly, wide, growly, like they have buzzing/humming AC
riding on top of them.
Additionally, the AA-230pro's manual says to make the 1/4WL stub with the
end of the coax OPEN. . . . .but then for the purposes of these tests, I am
using the stubs shorted.
Maybe I have a ground loop somewhere and there is feedback or an isolation
problem on the shacks's 120VAC line?
Mike
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