EMRFD Message Archive 2622

Message Date From Subject
2622 2009-01-22 18:14:36 ka3j12 DAC Control of VCO
Hi - This topic came up briefly at the end of May 2007. I wonder if
anyone here has actually tried to control a standard varactor-based HF
VFO (40-50 kHz tuning range) with a DAC or digital pot? I had two
different approaches in mind: one involving an 8 bit DAC or digipot to
handle xmit offset, RIT/XIT and stability compensation; or possibly
using a 12 bit DAC to control the tuning as well with roughly 10 Hz
steps at 1 mV per step. The former application would be easier and
would have 10 Hz steps at about 20 mV/step. This would be PIC driven
with a frequency counter in the control loop. Would appreciate any
thoughts and suggestions. Thanks.


Ron (KA3J)
2623 2009-01-23 14:19:41 joop_l Re: DAC Control of VCO
2625 2009-01-23 14:55:05 Johan H. Bodin Re: DAC Control of VCO

G0UPL has an impressive collection of information about Huff & Puff
stabilizers at http://www.hanssummers.com/radio/huffpuff/index.htm.

Johan SM6LKM

joop_l wrote:
> A DAC might be overkill. This is a PIC based PLL you might want to
> examine.
> http://homepage.eircom.net/%257Eei9gq/stab.html
> Also Elektor magazine presented a PIC PLL/stablizer several years ago.
> I know someone who built it. It meanders between two 10Hz points, but
> that probably is not a problem.
> This is probably the circuit:
> http://www.elektor.com/StreamFile.lynkx?path=Uploads/Forum/1829572760971.pdf
> Cheers,
> Joop
2626 2009-01-23 17:05:31 Jim Miller Re: DAC Control of VCO
look at the k3 schematic...


jim ab3cv