[HBR] HBR2K Chapter 10 -- It Takes A Lotta Parts To Switch Filters

[hbr@mailman.qth.net]

I initially hard wired the 2.4 kcs filter for all modes.   In the last day, I 
wired up the diode switching so the CW, 2.4 kcs, and AM filters are 
selected according to the mode.   

Other than the number of parts required -- both ends of each filter are 
diode switched -- the job was unremarkable.   After fixing a few wiring 
errors it worked the first time I turned it on.  I copied the circuit from 
the FT-101; the only novelty is use of filtered voltage from the 
cathode of the audio output stage to operate the switches.   

Then I dragged out the signal generator and checked the sensitivity.   
The 10 db s/n figures are:  80m -- 0.9 uv, 40m -- 0.6 uv, 20m -- 1.0 
uv; I did not check higher bands.   Some study and tuning obviously 
is needed.

One problem I already know about is low 1st oscillator output on the 
higher bands.   Also there's a bad trimmer on 80 meters so I think 
that band is not exactly peaked.  Yep, my 'parts' FT-101 may have 
really been junk -- shocking!

Walt Hutchens
KJ4KV