[Elecraft] K2 Transmit Test

[Don Wilhelm]

  Paul,

In addition to the points in my last post, a check of the feedpoint 
impedance (with an antenna analyzer) at the end of the parallel line 
would be informative.  If you have an 80 meter radiator and a feedline 
that is close to a half wavelength on 40 meters (34 feet or some 
multiple of that length), the feedpoint impedance will be very high.  
You might do well to  try adding a 15 foot length of parallel feedline.

I would advocate that a 1:1 balun will usually serve you better than a 
4:1.  It is not the characteristic impedance of the balanced line that 
is to be matched, but the actual feedpoint impedance of the feedline at 
the point where the balun is inserted - it all depends on the electrical 
feedline length and the electrical length of the radiator.

An 80 meter radiator used on 40 meters is "two halfwaves in phase" which 
has a high feedpoint impedance at the antenna feedpoint, one must use a 
balanced feedline that has an electrical length of 1/4 wavelength or an 
odd multiple thereof to bring the feedpoint impedance down to a 
reasonable level.

73,
Don W3FPR

On 5/4/2011 7:49 PM, Paul Agoglia wrote:
> I ran a transmit test today on my recently built (serial 7059) K2/100, with SSB adaptor,  KAT 100 antenna tuner and elecraft balun.  For the station antenna, I have an 80 meter dipole with each leg currently cut to 66 feet.  The center of the dipole is not quite 40 feet high.  The two ends are inverted downward  and are each 10 feet off the ground.  All three points of the antenna are anchored in trees.
>
> The antenna is fed to the shack with 165 feet of The Wireman 'window' ladder line
>
> I used my microphone to call a CQ on 40 meters, and the KAT 100 lit up like a Holiday Tree.  SWR all the way to the red zone.  I tried this at various power settings up to 100 watts, and only transmitted long enough to see how many lights I got.  Always to the end of the scale.  I used a separate SWR meter and was getting readings of 7:1.
>
> I switched to a 300 watt dummy load from the 80 meter dipole, and the SWR reading on the KAT 100 was perfect.  Just one light lit up.
>
> I also did a continuity check between the two lines on the ladder line to verify I did not have a short.  OK there.
>
> Any suggestions?  Is it possible that all I need to do at this point is trim the antenna?  Or do I have something internal going on?
>
> 73 de WN2K
> Paul Agoglia
>
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