[CQ-Contest] LP SO2R with no filters?

Jeff AC0C keepwalking188 at ac0c.com
Tue Jun 16 18:14:02 EDT 2015

The amount of work a guy may want to put into checking out the setup for 
isolation is in direct proportion to the cost of getting a potentially 
expensive RX repaired.  My view is that until you have TESTED to BE SURE the 
isolation exists, you have to assume it's going to fry gear.

And don't let the thought that "I'm only running 100W" be of any 
consideration.  That's +50 dBm and you want to be very much under +20 dBm to 
avoid damage - and less than that in some cases.  I think W2VJN recommends 0 
dBm as the damage threshold target.  That means you need 30-50 dB of 
isolation, on every band and directional combo - something which takes time 
to check out.   The isolation is easy to achieve with natural coupling loss 
and a stub.

You really will probably not be happy if you just try it, trusting luck 
alone, only to find out luck ends up against you.


-----Original Message----- 
From: Jeff Stai
Sent: Tuesday, June 16, 2015 12:31 PM
To: Mike Smith VE9AA
Cc: cq-contest
Subject: Re: [CQ-Contest] LP SO2R with no filters?

On Mon, Jun 15, 2015 at 2:53 PM, Mike Smith VE9AA <ve9aa at nbnet.nb.ca> wrote:

> Has anyone ever done SO2R with no bandpass filters?

Buy the W2VJN book from Inrad. It will explain everything:


But in a nutshell, just try it. It sounds like you have both horizontal and
vertical antennas, which will give you 20dB of separation at the outset.
That could very well be enough for your conditions. If you need more, stub
filters can be very effective for the cost of some scrap coax.

73 jeff wk6i

Jeff Stai ~ wk6i.jeff at gmail.com
Twisted Oak Winery ~ http://www.twistedoak.com/
Facebook ~ http://www.facebook.com/twistedoak
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