Steve,
If you have a large value trimpot at the output, that could cause
problems. Try a pot in the range of 500 to 1k. You may have to change
the values of the two capacitors in the base/emitter part of the circuit
for use at a lower frequencies. The capacitors control the feedback, so
some experimenting may be in order - either too much feedback or too
little can cause a failure to oscillate.
Remember that oscillator is intended to develop a huge output that is
handy for troubleshooting - the output is easily measured with an RF
Probe and DMM. If you want a low level oscillator better suited for
alignment purposes, I would suggest that you use a circuit similar to
that used in the Elecraft XG1 or XG2 - download the manuals and take a look.
73,
Don W3FPR
Elecraft Reflector wrote:
Hello Group!
I have built two crystal testers from the circuit shown on page 5, Appendix E
of the K1 construction manual. The components used were exact values. The
circuit works fine with crystals from 10MHz and upwards but good 80m crystals
will not fire up the oscillator. I have tried a fair few good 80m QRP crystals
(standard package) but no joy. Has anyone had the same problem? Any ideas how
to solve it please?
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