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 > > __
