[ARC5] My Little Converter Gets Weird...

[David Stinson]

I built another of my little converters to go in a second LF receiver
(corrected diagram):
http://home.netcom.com/~arc5/converter.JPG

I grabbed what I thought was another color burst xtal from the parts
bins at the goodies store.
I also deleted the 20-100 pFd trimmer 
and used a fixed 47 pFd cap, 
tuning the input with the slug in the coil.

It tuned up and worked fine, but 3880 KC 
was showing up at 339 KC, not 302.
There was also a large SWBC image just down from the 
"AM Ghetto."  I looked at the xtal and it's actually 
marked 17915 KC!  Try as I might, I can't seem to find 
any formula that gets 339 KC out
 with 17915 LO and 3880 input.  

For some reason, this one is more sensitive than the one
that used the color burst xtal, and a simple wave trap got 
rid of the image.  Anyone have a clue??

Also:  This set's T/R switches by killing the receiver B+,
and I didn't want to drill any holes to bring a PTT line or 
put in a clunky relay, etc.  So I built a voltage divider that
cuts the 250 VDC*  down to about 5.5 volts.  
I put 50-Kohms 2 watts in series with 2200 ohms 1 watt
and put a 6-volt, 1 watt zener across the 2200 ohm resistor to 
protect the converter, should a surge or resistor change bring
the voltage too high.  +5 to +6 volts available at the junction
and it works great.

73 Dave S.

*  Haven't tried low-B+ on this one yet.
    Will get to it some day......