To: Paul W8KC
RE: KX-1 operation on 160 and 80 meters
I saw your post about wanting a 160/80 meter KX-1. At first glance it seems
that a 2 band KX-1 with antenna tuner option could be modified as it is being
built to operate on 80 and 160 meters. Since no 30 meter board would be
installed there would probably
be room for the few additional parts required. Briefly, the pin 19 output of
U2 could be routed to a new NE-602 mixer with a
5.2 mhz oscillator crystal to reduce the pin 19 frequency by 5.2 MHZ. (The
display would read 7.0 mhz when you are on
1.8 mhz). The output of the added mixer would feed both Q4 and U6. If a 10.5
mhz crystal is selected, the display would
read 14.0 mhz when you are operating on 3.5 mhz. Please be sure to investigate
spurious mixer products before ordering
crystals, the above mixer scheme may not be the best. All capacitors and
inductors in tuned circuits would need to be approximately 4 times the value
used in the un-modified KX-1. Some bypass and coupling capacitors may need to
be changed. Also stage gain might need re-adjustment. Since the KX-1 processor
operates on 3.995 mhz, operation on the upper part, and possibly all of 75
meters may not be possible. Also urban folks may need to consider a highpass
filter in the receive input to reduce strong AM broadcast stations. Probably
the inductors and capacitors in the antenna tuner could be scaled up by a
factor of 4
to let you operate with a 100 ft wire and a 64 ft counterpoise. You might use
either a latching relay or the led lamp switch as a crystal bandswitch.
These are just some un-tried ideas....they are NOT exact designs. This would
be a fun project for someone with moderate design and building skills. I can
GUARANTEE that your radio would not play when you first turn it on. You would
need to do some engineering and experimentation to get it right.
Rick Dwight KL7CW
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