[CQ-Contest] SO2R technical questions

Jim Brown k9yc at audiosystemsgroup.com
Tue Jan 20 17:55:13 EST 2015

On Tue,1/20/2015 1:40 PM, Mike & Coreen Smith VE9AA wrote:
> How can I tell if I have too much energy at the input of "radio 2" when
> transmitting on "radio 1" ?

When the smoke comes out of the front end transistor.  :)

> Is this too much signal?

See above. W2VJN's excellent "Managing Interstation Interference" 
addresses this, and is a must-read. Lots of detailed advice, all of it 


> I can build some coax stubs over time.

In addition to the W2VJN book, also see k9yc.com/Coax-Stubs.pdf  for 
detailed advice and tutorial stuff that complements George's book. It's 
tricky to use stubs on multi-band antennas though -- you have to switch 
them, and both the switch and the coax between the switch and the Tee 
where they are inserted are part of the stub.

> ..and I am working on a YCCC SO2R box
> as time permits but don't have a lot of spare dough for BPF's (2 of them
> would run me $1200-$1400 CDN by the time I had them in the shack)

The TXBPF kits that 5B4AGN puts together are first rate, second only to 
the W3NQN-designed filters that Array Solutions sells for a lot more money.

> nor a SIX-PAK(another $1k_),

One of the YCCC guys has designed a kit to do that. Poke around for it.  
I'm thinking about building one.

> If I am willing to leave the amp turned off (sigh..), and antennas will all
> be separated only 50', how do I know if I have too much signal at the input
> of the 'other' radio?

> Oh and feel free to school me on SO2R

Practice, practice, practice, during contests, of course. I'm no expert, 
although I've been banging away at it for nearly 3 years, and gradually 
getting better. It does make most contests a lot more fun.

> p.s.- I will sorely miss using the amp, but if I try SO2R @ 100w and like
> it, maybe I can stumble onto some cheap 419 BPF's

You don't want one -- it's a dog.  Several years ago, I tested several 
bandpass filter sets and wrote up this review that eventually was 
published in NCJ.


I'd guess that in most contests, an amp is worth more than 100W SO2R.  
FWIW, NAQP is a great one to get your feet wet -- simple exchange, 100W 
max, no cluster.

73, Jim K9YC

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