[Elecraft] K3 at TI50DX

[Don Nesbitt]

I've had a number of emails "off list" inquiring about the use of filters
both between the K3's and the amplifiers and the amplifiers and the
antennas.  Jerry (W4UK) reminded me to be sure to post this answer to the
list least someone inadvertently sacrifice the front-end on their rig.

Note that as this was an SSB only contest, so we never had two rigs on one
band at the same time (as in - one on CW and one on SSB on 20 meters, etc).

Please keep in mind that good engineering practice would dictate the use of
a number of techniques to insure that RF in sufficient strength would not be
allowed to enter the frontend of any equipment.  Given the frontend
protection built into the K3, we felt fairly comfortable taking a minimum
approach.  YMMV (your mileage may vary) and I am in no way suggesting that
you do what we did!

Initially, we did have some fairly substantial "spits and sputters" between
bands even at the 100 watt level.  Armed with this preliminary information,
we tried using coaxial stubs to no avail.  Obviously, something else was
amiss.  A part of the next couple of days was spent taking care of cold
solder joints on the antennas and replacing some bad coaxial lines.  Once
this was done, our tests between Run 1 and Run 2, using virtually every
combination of low and high band antennas, indicated very little
interference without the use of stubs even as the power was increase to
contest levels.  
  
In the final equipment configuration, we used the Dunestar Model 600: Multi
Band Remote Switched Bandpass Filters between the K3's and the amplifiers.
These filters nicely cleaned up what little interference remained.

No filters of any kind were used between the output of the amplifiers and
the antennas.  Amplifiers used were:  Alpha 89, Henry 3K and Kenwood TL-922.

Many times we were running on 20 and 15 (quads on the same boom along with
10 meters) at the same time.  Frankly, it was quite amazing!  '73 -- Don

-----Original Message-----
From: elecraft-bounces at mailman.qth.net
[mailto:elecraft-bounces at mailman.qth.net] On Behalf Of Don Nesbitt
Sent: Tuesday, March 04, 2008 3:44 PM
To: 'Elecraft List'
Subject: [Elecraft] K3 at TI50DX

If you worked TI50DX this past weekend in the ARRL SSB Contest on any band,
you worked a K3.

Three K3's were used in our "multi-2" effort - two "run" stations and one
"mult" station.  All the K3's fed KW amps and frequently we were using a 3
element quad with individual band elements fed by separate feedlines on the
SAME boom with NO interference problems between bands!

Our TI50DX effort was to commemorate 50 years of the Southeastern DX Club
(www.sedxc.org).

Thanks to all who worked us and to all those who endured the contest.  '73
es gud dxing -- Don N4HH K3 #83

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