ICM can work from the schematic to determine the circuit capacitance.
ICM can work from an existing crystal to determine the circuit
capacitance needed. Working from the crystal is fastest. Tolerance is
based on how much you are willing to pay for dial precision.
Common capacitance values are 20 and 32 pf. In the 546 manual, I see two
47 pf capacitors in series, making about 24 pf. Adding a pf for the
diode, a couple pf for the transistor and circuit board makes about 27.
5 is a reasonable value for the switch and its wiring making 32 pf, the
most common stock crystal circuit capacitance. And I think ICM would
come to the same conclusion from their circuit analysis. I pretty sure
Tentec would have used the same circuit C for all radios so to prevent
confusion of crystal parameters different for different radios, just
like the crystal filters interchanged for several decades.
Remember that using these rigs on 18 MHz is OK for receive, but unwise
on transmit because the inputs to the transmit mixer are 9 and 9.1 MHz
with second harmonics at 18, and 18.2 MHz, especially the 18.2 (varied
by the PTO) will come out of the antenna.
Some one at Tentec probably knows these parameters and has them on the
tip of their tongue and might even have the crystals on hand at a better
price than a custom crystal.
73, Jerry, K0CQ
On 1/28/2011 11:14 AM, Bill Acito W1PA wrote:
> Anyone know the Ten Tec part numbers for the WARC crystals for the Delta
> (580) and the Omni-C (546)? I know the frequencies from the manuals, but the
> manuals don't list their part numbers. I assume they were in the docs when
> ordered from Ten Tec. Checking here before I bother Ten Tec.
> I am working with ICM to get replacements.
> Bill W1PA
>> I have information on the 580 delta. Do you have the Ten-Tec part numbers
>> for the crystals you need. I do not have any information on the Omni-C, I
>> will need the load and tolerances.
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