In the last few months (year?) Elektor magazine published a circuit
of an RF  frequency stabiliser based on a 16C54. (I can probably dig
the article / reference up if required)

The original circuit is meant to prevent drift in a VFO once it has
been manually tuned.
The circuitry could probably be used essentially unaltered for
control of a series of preselected (or remotely input) frequencies.

As I recall the PIC applies error signals to a capacitor via
resistors (simple integrator) which controls a varicap VFO. I think
it had "fast" and "slow" resistors. Presumably these were drive n
either high, low or O/C.
VFO frequency is read by the PIC along the lines of the recently
discussed frequency meter.


    Russell McMahon


From: Chris Eddy <ceddy@NB.NET>
>I haven't done a PLL, but may have to on another project soon.  I
thought
>of coupling a PLL and PIC, but the customer wants an ultra low cost
>device.  Would it be possible (possible for sure, practical is the
>question) to couple an R2R or other DAC to a variable cap diode in
an RF
>circuit, then come back through a prescale into the PIC so that the
PIC
>can monitor frequency.  In this manner, the PIC can take charge of
the
>many PLL tasks, except for the RF portions.  My application would
only
>have to account for temp drift, and as such the PLL doesn't have to
have
>massive performance.I want to give the user easy selection of five
major
>transmit frequencies without any complex factory tuning.
>
>Starfire Zhu wrote:
>
>> Hi PIClisters,
>>
>> Does anyone have experience in progamming a PIC to control a
MB1511 or
>> the like? Please shed me a light.
>>
>> Thanks in advance!
>> --
>>                 __________________________________________________
>>                 :-))   TEL: 86-756-2236157  2115540   FAX: 2115541
>>                 :-))   Email: zhuxh@cheerful.com      ICQ#:7037093
>>                 ==================================================
>