[Elecraft] K3 SO2R Question

[Bob Naumann]

Jim,

Are you asking if you can run high power SO2R and do so safely without
bandpass filters? You didn't mention what power level, and this makes a huge
difference.

You can use ICE bandpass filters (-30 to -35db) which are relatively cheap
(~$40 each). Their performance is not as good as W3NQN design filters (-75db
to -80db) which are the ones that cost big bucks(~$99 each). If you allocate
one radio to doing say 160, 40 and 15 and the other to doing 80, 20 and 10m,
you could get by with just one set of 6 bandpass filters.

While bandpass filters have a by-product of protecting your radio's front
end, that's not all they do. The filter on the transmitter limits what gets
out and the filter on the receiver limits what gets in - so having a filter
on each radio increases the benefit. This is more of a practical operational
thing than being protective. 

Also, when you say "separation of frequencies within the band" do you intend
to run both radios on the same band? Needless to say, bandpass filters will
not be of any use if you do this. The key here is physical separation of
your antennas so that the coupling between the two is minimized.

Bob W5OV

P.S. ICE has a new owner and is delivering product again much more quickly.


-----Original Message-----
From: elecraft-bounces at mailman.qth.net
[mailto:elecraft-bounces at mailman.qth.net] On Behalf Of Jim Harris
Sent: Monday, March 08, 2010 4:03 PM
To: Elecraft Email
Subject: [Elecraft] K3 SO2R Question


Hi Folks,

I'm currently selling an off-shore rig with the hopes of acquiring a second
K3 for SO2R, primarily for RTTY contesting.  I believe I've seen somewhere
in the not to distant past that is was said the K3 receive front end can
withstand 1-2 watts without damage.  I've spent the last hour reviewing the
email archive and can find no reference to that.  Can anyone confirm or deny
my remembrance?  (Or, is it all just wishful thinking?)  Is there anyone on
the reflector that is operating a K3 SO2R station without the thousand or so
dollars of band pass filters needed to protect the radio's front end?

Second part of the question is.....if possible to not damage the front end,
what is the possibility of desensing or causing blocking or noise that would
interfere with reception on one receiver when transmitting on the other
radio.  I'm sure that is highly dependent on band(s) and separation of
frequencies within the band.  I'll fully aware of the K3's ability to
completely block signals a few kilohertz away but when RTTY contesting I do
seem to notice there may be some desensing or AGC action from these signals
even though they are not heard or processed by MMTTY.

Comments very much appreciated.

CU in the Colorado QSO Party Sept 4th, 2010.

73,  Jim, W0EM


 		 	   		  
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