[CQ-Contest] SO2R Technical Question - Round II

[Jim Idelson]

Lee,

You've just begun to scratch the surface of the interstation interference 
problem. There are a lot of things going on, and the filters actually serve 
multiple purposes. Rather than go into it here and be redundant and offer a 
less than complete answer, I will suggest looking at this teaser by my friend 
W2VJN . . .
http://www.inrad.net/files/Pubs/managing-interference-ch1.pdf

And then I suggest very strongly that you purchase the entire book for just 15 
bucks. It is not a complex presentation, but it covers all the right material, 
and it suggests practical solutions. I own two.
http://www.inrad.net/product.php?productid=248&cat=148&page=1

And everybody else on this reflector should buy a copy, too.

[George, pay me at Dayton.]

73,

Jim K1IR

[CQ-Contest] SO2R Technical Question - Round II
from [Lee Buller]
[Permanent Link][Original]

To: 
CQcontest Reflector <cq-contest at contesting.com>
Subject: 
[CQ-Contest] SO2R Technical Question - Round II
From: 
Lee Buller <k0wa at swbell.net>
Date: 
Wed, 23 Jan 2008 14:00:16 -0800 (PST)
List-post: 
<mailto:cq-contest at contesting.com>

After reading quite a bit on the WWW about SO2R....

I am assuming that you place band pass filters (what ever ilk) in line with 
BOTH radios.  That being the case (if it is) then using bandpass filters on 40 
you would be knocking down (but not eliminating) the harmonics on 20 meters.  
In addition if you have a 20 meter filter on your second radio, that do would 
have attenuation on the 7 Mhz energy.  So if the transmit filter on 40 
is...say....40 db down and the receive filter on the 20 meters station is 
another 40 db down....would not those figures combine?  That is a question!  
So, you are protecting the 20 meter radio from the 40 meter radio.  

That means you would have to have filters for 6 bands times 2 or 12 filters. if 
you were running 160, 80, 40, 20, 15, and 10 meters.  I guess you could use a 
manual six position switch to select the Radio 1 filter and the Radio 2 filter. 
 That would mean using passband filters...that you would need to switch the 
filter to the band you were on and all is well.  Now, alot of S02R ops use 
automatic switchers (I am sure they found that to be less expensive in the long 
run that sending in the radio for repair)...but one could get away with the 
manual switch if you were "careful."  This is only a good way of doing things 
if it is a bandpass filter.

Is the logic OK....I know I am running in the dark with a pair of scissors?

I hope I am not showing my stupidity here....but I am learning.

Lee - K0WA
"I think I barefoot too"

 
In our day and age it seems that Common Sense is in short supply.  If you don't 
have any Common Sense - get some Common Sense and use it.  If you can't find 
any Common Sense, ask for help from somebody who has some Common Sense.  Is 
Common Sense divine?

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Jim Idelson K1IR
email    k1ir at designet.com
web    http://www.k1ir.com