[time-nuts] Small quantity custom crystals
lous at xs4all.nl
Sat Oct 2 13:22:51 UTC 2010
I have had good results with the part if this circuit around T1.
Varying L1 selects the right overtone for basic operation.
The collector circuit here has a coupled resonator tuned for the 144,
but it will probably work equally well for 216. A cheap (fundamental)
24Mhz computer crystal operating at 72 MHz will get you there. Just
alter the filter for 3 x 72 instead of 2 x 72. Note as someone else
posted that the frequency at 72 may be tens of KHz higher than that.
Each brand or even each individual crystal will vary here.
You could also stick to the collector circuit from your tracker
transmitter circuit if you want to keep things as small as possible.
It worked down to 1.1V in bench tests with a MPSH10 transistor.
Tuning the bias with R2 helps to optimize the power for the desired
output frequency. More bias then necessary will only consume more
battery power and not contribute to the output. Actually power output
may be less. For more insight look here:
Joop - pe1cqp
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