PLL chips that are quite good can be purchased for less than $2, the bigger problem is finding a VCO with wide range and low jitter and phase noise. The only one I've found that I'm happy with the specifications is from Mini-Circuits and runs in the 600MHz to 800MHz range but cost about $38, the extra division to get your final frequency helps cut down the noise.
If you want to limit yourself to a smaller tuning range then a conventional low phase noise oscillator controlled by a PLL chip would be a good alternative. I've been thinking of building a PTO controlled oscillator with a small vari-capacitor to lock it on the "channel" with a National PLL, the channels would be somewhere in the 20KHz range. At 10:26 AM 6/10/2006, you wrote: >In response to the statement that everybody finds A/D interesting, I'd make >the comment the everybody finds the DDS interesting. > >With the technology of Softrock as it is now, the DDS posses little >advantage as a frequency source and many problems. Let me suggest that a PLL >would be a better frequency source. The thing that I suspect everybody is >thinking is that with a DDS you can have continuous tuning. Well the same >thing could be achieved with only a bit of help for Rocky or one of the >other software packages. > >The complaint with a PLL is that it moves in discrete jumps, that seems >appropriate for channalized radio but not for continuous tuning. Borrowing >from the channel concept, what if the PLL jumped 12.5 KHz (it's PDF >frequency) but the Rocky software being aware of this could shift up or down >by the same amount, therefore keeping the signal of interest in a useful >position with the ability to tune up or down another 12.5KHz. Actually, I'd >let Rocky tune perhaps +/- 15KHz before issuing a command to change the PLL. > >I think that this proposal would make a whole lot more since than a lot to >frustration with the DDS and it's high cost, a PLL can be had for one tenth >the price. > >Cash Olsen, KD5SSJ > >Kits to build Scotty's Spectrum Analyzer http://www.zianet.com/erg >Scotty's Spectrum Analyzer website http://users4.ev1.net/%7Ewsprowls/ >Yahoo Builders Group http://groups.yahoo.com/group/spectrumanalyzer/ > >-----Original Message----- >From: [email protected] [mailto:[EMAIL PROTECTED] On >Behalf Of [EMAIL PROTECTED] >Sent: Friday, June 09, 2006 11:49 AM >To: [email protected] >Cc: [EMAIL PROTECTED] >Subject: Re: [soft_radio] Re: A/D Idea > > >Alberto: > > Everyone seems to find A/D interesting. I believe though that the >simplicity of the sound card will remain most useful with the majority of >people. The A/D idea may be mostly taken up by manufacturers of radios with >special software for that particular radio. > > But I will keep an eye out for the developments. > >ka9rza > > >_____________________________________________________________________ >Call Anyone, Anytime, Anywhere in the World - FREE! >Free Internet calling from NetZero Voice >Visit http://www.netzerovoice.com today! > > > > > > >Yahoo! Groups Links > > > > > > > > > > > > >Yahoo! Groups Links > > > > Cecil Bayona KD5NWA www.qrpradio.com "Windows the worlds most successful software virus" ------------------------ Yahoo! Groups Sponsor --------------------~--> You can search right from your browser? It's easy and it's free. See how. http://us.click.yahoo.com/_7bhrC/NGxNAA/yQLSAA/ELTolB/TM --------------------------------------------------------------------~-> Yahoo! Groups Links <*> To visit your group on the web, go to: http://groups.yahoo.com/group/soft_radio/ <*> To unsubscribe from this group, send an email to: [EMAIL PROTECTED] <*> Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
