[CQ-Contest] 40m to 20m interference

[Edward Sawyer]

Jeff, 150ft of separation is plenty for 100W and 40M/20M 2 radio operation.  You will hear the 2nd harmonic on 20M when transmitting on 40M.  But that harmonic shouldn’t be higher than S9+40db and it shouldn't affect more than 5 - 10khz on SSB or 1 - 2 khz on CW.

If the coax cables are solid shield across your entire system, the BPFs work, and 2 radios are commonly grounded, this should be the result.

The stub would be to suppress the harmonic described above.

Ed  N1UR

-----Original Message-----
From: CQ-Contest [mailto:cq-contest-bounces+edwards=sbelectronics.com at contesting.com] On Behalf Of Jeff Blaine
Sent: Wednesday, January 22, 2020 8:33 PM
To: cq-contest at contesting.com
Subject: Re: [CQ-Contest] 40m to 20m interference

Bill,

There is no such thing as an easy answer on this.  But with a bit of 
study, you can get a handle on the issue and the magnitude of the fix 
needed.  I would recommend you track down the W2VJN book "Managing 
Interstation Interference."  It's got everything you need to get this 
under control.

https://toptendevices.com/products/managing-interstation-interference-2nd-edition-by-george-custogeorge-w2vjn/

73/jeff/ac0c
alpha-charlie-zero-charlie
www.ac0c.com


On 1/22/20 5:00 PM, William Hendrick via CQ-Contest wrote:
> I have a lot of interference on 20m when TXing on 40m even with BPF on each K3 running 100w. A 23' shorted stub at the 40m rig doesn't seem to help. Both antennas are Butternut verticals about 150' apart. Am I asking too much for the filters with the same antenna polarization and spacing?
> Bill, N0AC
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