[Elecraft] K2 Antenna Tuner Question

[Vic Rosenthal]

"Julian (G4ILO)" wrote:
 
> So, a couple of weeks
> ago, I swapped the SG-239 for a 4:1 balun and connected this via about 2.5
> metres of RG-213 to the K2 in the room below. I expected to be
> disappointed, and for this to work not as well as the previous arrangement.
> Boy, was I in for a surprise!
> 
> When I switched on, signals on 20m seemed to be about couple of S-points
> stronger than before. 

I found this report fascinating, since I have played a bit with autotuners.  One
possible explanation is that the SG-239 at the feedpoint was facing an impedance
near the end of its range (perhaps very low), causing its efficiency to be
poor.  When you switched to the KAT2, it was seeing a different impedance, as a
result of 2.5 meters of coax and the balun.  This impedance may have been much
more reasonable, so the KAT2 was able to match it more efficiently.

One way to test this is to turn off the KAT2 and connect the SG-239 directly to
the K2, and then have it feed the coax/balun combination.  If it works as poorly
as before, you can conclude that the SG-239 is inferior to the KAT2.  If it
works as well as the KAT2 or close to it, then you know the probalem was that
the impedance at the feedpoint was unfavorable.

Of course, the KAT2 has other advantages, such as not needing to sense RF to
select the appropriate parameters when you change bands and per-band antenna
switching.

Vic K2VCO