[Elecraft] Resolving AGC activation from Broadcast Stations

[Marteinn Sverrisson]

Resolving K2 S-Meter activation from broadcast stations

I have had trouble with S-meter/AGC activation from short-wave broadcast
stations on 40, 20 and 17 meter bands on my K2. The largest S-meter
indication S9 (SSB mode), being on 17m.
I traced this to leakage to the SSB module, as the activation was much
stronger on SSB (S9) than on CW (S5).

Moving I.F. Out to output of 2nd Xfilter

I then looked at the K2 schematic and observed that the I.F. OUT signal
to the AGC/S-meter circuit is picked up ahead of the 2nd Xtal filter
instead of after it. 

So I removed the capacitor C181 and routed the IF signal from output
of the 2nd Xtal filter, to the AGC circuit.

Connected pin 1 of the product detector U11,
via 1.5 kOhm + 0.01uf (C181) to I.F. OUT, removing
the 5.6 kOhm resistor previously inserted by the 2nd Xfil mod.

This did the trick, I now have no S-meter/AGC activation from
broadcast stations even if their signal strength is S9+40dB on the 17m band.

73's de TF3MA

http://www.raunvis.hi.is:~matti/TF3MA