[CQ-Contest] Coax Stubs for SO2R

rob wa1fcn at charter.net
Fri Oct 2 14:21:16 EDT 2015

On 9/8/2015 5:22 PM, Peter Voelpel wrote:
> 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,

             What would you recommend if you had  2 el 40 on one tower 
and  tribander
             on second tower.  I have considered experimenting  with 
so2r  but just 20 and 40
              meters to see if I can handle it.
                     BoB WA1FCN

> 73 Peter -----Original Message----- From: CQ-Contest 
> [mailto:cq-contest-bounces at contesting.com] On Behalf Of Mike Smith 
> VE9AA Sent: Dienstag, 8. September 2015 23:14 To: 
> towertalk at contesting.com; cq-contest at 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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