[Elecraft] FYI - Low sensitivity / VFO (aka Gary Surrency Rocks)

[Garth Hitchens]

I just have to rave about the support I got from Elecraft, and point out a
potential problem for others.  I built a K2 months ago and always felt like
it wasn't quite as "hot" a receiver as I expected, but it worked ok
otherwise, and certainy well enough compared to some other rigs I had.

Recently, I built the 160 module for my K2, and had problems getting more
than a few watts out at the band edges, or more than 7 in the middle.  I got
no HI CUR warning, just couldn't drive it more than a few watts out.

After a few emails with Gary Surrency I had ruled out problems in the
bandpass filters, low pass filters, and power amp circuits.    After I told
Gary I was using a scope,  he happened to mention to me during this to "make
sure that you have about 2.2-2.4v p-p on TP1 (that would be about
0.78-0.85Vrms as an RF probe would measure)".   Bingo!   Mine had about
1/5th that value.   That turned out to be my problem - I had a bad solder
joint on a capacitor near the input side of the VFO buffer amp.

After repairing the solder joint, not only was I able to drive 160 to full
output all across the band, but I also had a much hotter RX as well (didn't
need the preamp anywhere near as often!).   So, if you're suspecting low
sensitivity and have problems with power out on 160, measure your VFO output
at TP1 with a scope or RF probe, you might have a low VFO output.

Garth KG7GA