[ARC5] Crystal Alternative

[Robert Nickels]

I've shared the following on a couple of groups and since many of you 
are already familiar with these parts, I figured it would make sense to 
pass it along here as well.    Please contact me off-list for additional 
information or questions since this is somewhat off-topic and shameless 
commerce, thanks.

73, Bob W9RAN


The announcement of the impending closing of International Crystals has
many people thinking about frequency control, which is essential to keep
many of our older radios on the air. The fact is, International is
closing for a reason - modern radios and electronics in general simply
do not generate much demand for standard quartz crystals, and it is even
more challenging to sustain any kind of one-off custom manufacturing
business.

Fortunately, modern technology provides alternatives. Since shortly
after my SDR converter article appeared in Jan. 2013 QST, I switched to
programmable oscillators made by Epson in a 4 pin DIP (non-SMT)
package. These are complete crystal-controlled oscillators with
integrated PLL circuitry that is programmed by the distributor (DigiKey)
to produce an output on any specified frequency from 1 to 125 MHz. The
accuracy is stated as 50ppm but I've consistently found it to be better
than that. These are fixed-frequency devices and cannot be
reprogrammed, nor can they be shifted in frequency by external
components such as is done by "warping" a quartz crystal for clarifier
or RIT, VXO, or FM modulator circuits.

However, they are great fixed frequency sources for receiver local
oscillators, up- or down-converters, SSB high frequency oscillators, AM
or SSB marine radios, and transmitters/transceivers. The output is a
5 volt p-p square-ish wave but this has not been a problem since
whatever harmonics are present are filtered out by existing tuned
circuits in the radio. It is usually possible to obtain proper mixer
operation by simply coupling the output to the crystal socket, but some
crystal-controlled transmitters will require an added external amplifier
to raise the drive level to that required for full power output.
Naturally, the application of these devices is the responsibility of the
user.

I have created a small PC board (2" square) to facilitate the use of
these programmable oscillators. The board has sockets for 1 to 4
oscillators (4-pin DIP package) and provides full buffering of all
control and signal leads to protect the delicate oscillators from
inadvertent damage. The board includes a voltage regulator that
accepts 8-18 volts input and requires a switch closure to ground or
logic level "0" signal to select a given frequency. For more information:

http://www.rantechnology.com/four-channel-oscillator-board.html

I've got a limited number of kits available for the price of $18 each,
postpaid in the US. If you're interested in one, please drop me a
private email and I will provide details. Note this is for the
four-channel board only; you must order the oscillators directly from
DigiKey (current price is $4.10 each, qty 1-10, specify desired
frequency in MHz in "Order Notes").

Based on our shared interest in restoring and using military radios I
wanted to give the group advance notice of this alternative.

Thanks and 73,

Bob W9RAN