The Huff and Puff moves the frequency to correct for drift and that is the key. Careful design and construction of the VCO will give you low drift therefore not many corrections.
At 12:10 PM 6/10/2006, you wrote: >Hi Cash, > >I mostly agree with you. The fact that the tuning is done in discrete >jumps is not a problem as long as the steps are small enough. >The advantage of the DDS is the very good phase noise characteristics, >the disadvantage are the spurs. The newer DDS are much better and if >clocked at 500MHz and up the spurs won't be such a problem when >generation low frequencies. The problem is the clock which is >difficult to make, especially with a low phase noise, the price and >the packaging of these new DDS does help either. >The problen with a PLL is to get a very low phase noise. >To get very good performance with a SDR is to have very low noise >oscillators. >Right now I am building one for 50 MHZ using a softrock V6 as a 9 MHZ >IF. The 9 MHZ oscillator (36MHZ or 12 MHZ is using 3rd harmonic >sampling) will be an Xtal oscillator and it should be easy to have a >low phase noise. >Ahead will be a low noise preamp followed by a mixer driven by a >variable LO and I am looking for some ideas for that oscillator. I was >thinking of a Huff & Puff, but the problem is that the oscillator will >toggle between 2 frequencies separated by the value of the step, not >good when listening to CW with a very narrow filter. As far as PLLs >are concerned the CDG-2000 PLL seems interesting but is rather >complicated and use a DDS difficult to get and pricey. >Does anyone as any idea? > >Jean-Claude PJ2BVU > >--- In [email protected], "S. Cash Olsen" <[EMAIL PROTECTED]> 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 --------------------~--> Protect your PC from spy ware with award winning anti spy technology. It's free. http://us.click.yahoo.com/97bhrC/LGxNAA/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/
