What you want to build is a frequency locked loop. This stabilizes the
oscillator frequency but does not use the loop to clean up the
phase noise.

Wayne Ryder a friend built a General Coverage receiver using this
method. It worked quite well. The key is to make sure that the LO
phase noise is clean enough to meet your requirements.

Norman Gillaspie

> -----Original Message-----
> From: pic microcontroller discussion list
> [mailto:PICLIST@MITVMA.MIT.EDU]On Behalf Of Chris Eddy
> Sent: Friday, November 06, 1998 7:13 PM
> To: PICLIST@MITVMA.MIT.EDU
> Subject: Re: VHF PLL controlled with PIC
>
>
> Starfire; (Former anger set aside)
>
> 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!
> > --
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> >                 :-))   Email: zhuxh@cheerful.com      ICQ#:7037093
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