[TowerTalk] station to station interference

[Roger (K8RI) on TT]

Jim, how did the 6-pack construction compare to 4O3A's 8 X 2? I have a 
6-pack and IIRC it uses open frame relays.
  As for the filter sets, I'm about the only one running SO2R in this 
area, that is, if I ever get it back together.

73

Roger (K8RI)

On 9/28/2016 Wednesday 1:07 PM, Jim Brown wrote:
> On Wed,9/28/2016 5:54 AM, Ed Sawyer wrote:
>> I would advocate "going clean" on the worst offender scenario and 
>> have pure
>> coax going from the amp to the antenna.
>
> Yes. I had more crosstalk between stations than I thought I should, 
> and SWR was higher at different points in the station than made 
> sense.  I bought  a big spool of BuryFlex and 100 or so 83-1SP 
> connectors and replaced every piece of coax inside my shack, starting 
> with my entry panel. I also replaced a Daiwa power meter with N8LP's 
> LP100A, and got rid of sampling points to look at harmonics on a 
> spectrum analyzer. And I replaced a Six Pak with 4O3A's 6x2 (and a 
> year ago,with his new 8x2).
>
> I'm using several Top Ten relay boxes (some 6x2s to switch stub 
> matching networks for my 80 and 40 dipoles, and some 2x1s to trade 
> several antennas between the two radios). Taking apart one of the 
> 2x1s, I learned that they fail to provide a return path for RF current 
> on the circuit board -- the only return path is the chassis -- so SWR 
> is a mess at 10M and 6M, and while I didn't measure it, that sort of 
> thing also can increase crosstalk. I rebuilt those boxes to add a 
> return path paralleling the center conductor path, and the SWR through 
> the box dropped by more than half.  The failure to provide a return 
> path is all too common in HF antenna switching systems and antennas. 
> It's present in the big Ten Tec tuners (229, 238), and in several 
> expensive high power antenna tuners I inspected in booths at Dayton a 
> few years ago. When I pointed it out to the engineer who designed 
> them, he didn't understand the problem. This can also be critical in 
> filters. 5B4AGN has done an excellent job with his design of the TXBPF 
> filter sets for which he's arranged several group purchases.
>
> Ten Tec did it right in the power amps that I own (Titan 425 and Herc 
> II) -- there's coax from both input and output to the vacuum relay.
>
>> By the way, I don't need stubs - I have found out.  Just Bandpass 
>> filters
>> and antenna separation.  1.5kW on all bands and SO2R.
>
> You must have a LOT of separation. Where I think most of us run into 
> trouble is between 80, 40, and 20 CW, because the harmonics end up 
> where we're likely to want to operate on the higher band.
>
> 73, Jim K9YC 


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