Hi Ignacio, Thanks for your response. And in theory of course you are correct.
However, I have much experience in this field using very simple equipment. Take a look at the attached link: http://www.nzart.org.nz/contests/2007/DougGormanMemorialFrequencyMeasuringContest2007.pdf You will see that the three joint ZL competition winners in 2007 (I was one) all had zero error (less than 0.1HZ). Even the fourth place entrant had average error of only 0.17Hz on three different frequency measurements!. In my case I used only a standard Icom 7000 plus a PC running MixW software in PSK31 mode. At least one of the other two winners uses a Rubidium standard I know that. The secret for me was to have 0.1HZ resolution - via MixW - plus visual averaging of phase display over 5-10 seconds. And of course check before and after against WWV on 2.5/10/15. So it can be done. For new SDR software all that is need is to look at Sigmira software phase display method and if possible provide 0.1Hz resolution instead of 1Hz. 73, Chris ZL1BOE http://www.nzart.org.nz/contests/2007/DougGormanMemorialFrequencyMeasuringContest2007.pdf You will --- In [email protected], EB4APL <eb4...@...> wrote: > > Chris, > > Regarding the 0.1 Hz or better resolution you will have to face 2 > problems at least: > > 1.- If you receive WWV via ionospheric path (like you and me) you will > see that the frequency can't be adjusted to better than 1 Hz or so, the > path length changes so much (and so the phase display) after a few > seconds that trying to go beyond that is frustrating and impractical. > > 2.- Unless your receiver has a very stable frequency reference (an OCXO > or the like) the frequency shifts several Hz due to temperature changes. > > I have been there. I have a SDR-1000 and it allows very fine frequency > offset adjustment, but it is useless trying to adjust it below a Hz, > unless you use an external very stable reference and you calibrate it > using a rubidium or GPSDO. > > In fact, if the receiver uses a sound card, the sampling frequency > stability of your sound card also affects the frequency calibration. As > far as I know, the guys currently involved in the frequency measurement > contests uses quite sophisticated equipment and calibration techniques > these days. > > 73 de Ignacio, EB4APL > > > CHRIS wrote: > > > > > > Hi Alberto, > > > > Many thanks to you - and others - who answered my post. > > > > First, I should make it clear I am not a programmer and am quite new > > to SDR. But longtime ham and enthusiast for digital modes, remote > > radio control etc. > > > > I first read about polyphase FFT on Alex VE3NEA website. > > > > http://www.dxatlas.com/Rocky/Advanced.asp > > <http://www.dxatlas.com/Rocky/Advanced.asp> It is most interesting. > > > > However, I may be confusing Polyphase FFT technique with the Rocky > > waterfall display which is attractively different to other SDR programs. > > > > Second, regarding frequency resolution. No, I am not referring to the > > excellent lower waterfall window of WinRad - rather to the ability to > > read/adjust the LO and TUNE frequency readouts with increased > > resolution - down to 0.1Hz. Winrad HD is already a step in the right > > direction with 1Hz resolution - as is Sigmira. Sigmira is also worth > > looking at as it allows modes AM, LSB, USB etc all drive the phase > > display, allowing the frequency readout to be closely synchronised > > with WWV or any other signal. So in a few seconds you can see the tue > > carrier frequency displayed to within 1 Hz. But even 1Hz resolution is > > not enough to bring the Sigmra phase display to a complete stop on my > > SDR-IQ. For that 0.1Hz control would be better. Plus the ability - > > like Sigmira - to make a semi-permanent correction to the inherent NCO > > error in the SDR-IQ - around 185Hz at 15MHZ in my unit. Maybe I don't > > understand how to compensate clock frequency in SDR14/IQ control panel? > > > > One other thing I omitted to mention in my original post is to ask if > > a future SDR program might be based on seperate server/client > > architecture? This would allow location of SDR at a remote site and > > control via internet? I think SpectraView 3 can do this but it is not > > as useful for ham radio applications as WinRad. A question - what > > broadband data rate would be needed to reliably operate a remote > > SDR-IQ for instance? > > > > Finally, I must emphasise that WinRad is a clear favourite for me in > > most respects over the other programs mentioned. So my suggestions are > > made with respect to making an already fine program even better! > > > > I will be following future discussion with grat interest! > > > > 73, Chris ZL1BOE > > > > __ >
