Paul, Jim,
Thanks for your responses. I have no idea where these crystals came from,
but I've had them for quite some time.
I took some time to match up what I could by measuring the frequency of
each in an oscillator circuit. I have seven extra sets of crystals that I'd
like to offer to anyone who may want to try to build a 30 meter set with
this IF frequency. There are six crystals per set. Four are matched within
20Hz for the IF filter, and two others that are close by for the BFO and
transmit mixer. I'll have to find some padded envelopes before I send them
out.
Let me know if you'd like a set and I'll get them in the mail as soon as I
can.
Regards,
Mike M.
KU4QO
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On Thu, Nov 23, 2017 at 7:52 PM, Jim Kortge <jim.k8iqy@...> wrote:
Mike et. al.,
I just ran a design using the Goldmine Electronics 13.5 MHz crystals that
Chuck sent to me many, many moons ago. Using the AADE Filter program and
the crystal parameters from my web page that I measured a long time ago, it
looks like a 500 Hz Cohn filter can be made. The insertion loss is a tad
high, about 9 dB, but that isn't too bad. Those crystals have a very low
equivalent resistive loss. You'll need to make the coupling capacitors
from a 0.001uF in parallel with a 150pF to get the correct value. Also,
the drive and terminating impedances are quite low, about 10.2 Ohms, so
that will need to be matched to make the filter work. I'll post the
circuit schematic and response files in the files section after I send this.
72 and good luck,
Jim, K8IQY
