On 07.06.2013 19:23, Perry Sandeen wrote:
List,
Another hardware possibility.
Double the 10 MHz to 20 MHz.
With another circuit of 74HC390’s divide 10 MHz to
200 KHz. Then double it twice to 800 KHz
with LM 1496 DBM’s. Apply the two
frequencies to a LM 1496 DBM and use a LPF to get the 19.2 MHz.
Hardware complicated? A bit.
Only a bit? Only the filter to rejetct the products that you will have
spreaded in all places, spaced 200kHz, and mainly to remove the 20.8
MHz spurious that you will have as a result of the last mixing, makes
this approach difficult. I would favour a PLL, and since for the
application, short-term stability seems unrelevant, even using a
conventional VCO and not a crystal would be enough. A 74HC4046 can reach
19.2MHz, and you only need a couple of dividers to get a 200kHz
reference to feed it.
However one doesn’t have to search for a microprocessor that you program
and may not be available in a couple of years. The IC’s are cheap and have
been and will be around forever.
The LM1496 was discontinued long ago.... it was a second source of the
MC1496 (that is in production). But never think it will be around
forever (yes, as a hobbyist, surely you can find a single piece forever,
more if price does not matter too much). Also, I'm not a bit fan of
PICs, quite the contrary, but for example the PIC16F84 has been
available from more that 16yr and it is on production... so following
your LM1496 criteria, will be available forever :)
IMHO sometimes an older *brute force* circuit
proves that more can be less in implementing what you desire to accomplish.
Brute force is usually brute :)
Regards,
Javier
Regards,
Perrier
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