yup, and i bet Mssr. Fourier had no clue what we would with his 'transform' either...
73, w5xz, dan --- On Tue, 6/5/12, Brian Lloyd <[email protected]> wrote: From: Brian Lloyd <[email protected]> Subject: Re: [FlexEdge] two 6500s = one 6700? To: [email protected] Date: Tuesday, June 5, 2012, 3:36 PM > > > On Mon, Jun 4, 2012 at 12:15 PM, Stephen Hicks, N5AC > <[email protected]>wrote: > > > >> Brian, > >> > >> The real problem here is that even though you could maintain > >> synchronization if you were phase-locked to GPS, you would lose > coherency. > >> There are methods to fix this, but it is complicated and the PC > >> isn't going to help with the problem. > >> > > > > Ah, I assumed (silly me) that the timestamps on the samples would be > > of sufficiently fine granularity to allow preservation of phase > information. > > > > ;-) The phase of what, precisely? If you think about it, the phase of > signals themselves is preserved with IQ data and the time stamp of the data > tells you when it was collected, but this is not the problem. That's about > all I'm willing to say about that. > Ah, now you are being pedantic! That is my job! :-) I think of time intervals less than a wavelength to be phase information. I also tend to fall back on my astronomy days and think in terms of wavefront preservation. In any large mirror, if I can maintain its surface correctness to better than 1/8 wave (resulting in preserving the wavefront to better than 1/4 wave) then I retain my ability to image the source accurately. So, we take multiple radios, sample, timestamp the samples with an error of less than 1/8 wave at the frequency in question, and then if we know the locations of the antennas to an accuracy of better than 1/8 wave, we have the ability to recombine all the sample information to "image" the source. The possibilities for "beam steering" and studying the vagaries of the Heaviside Layer (it just sounds so much more mellifluous than "ionosphere") are boundless. No other radio existing or proposed for amateur use (at this time) offers such possibilities. So, yes, you are right, we are not really preserving phase as we are preserving location information as a function of time. (Think GPS types of calculations being done at HF.) Am I making any sense? It is so obvious to me in my head but less so when I try to put it into words. <sigh> But you don't need to be so cagey. None of this is rocket science. It is something that has been done at great expense elsewhere but now falls into the reach of amateurs. I have no idea what this will produce (well, I have a few ideas and lots of potential experiments in mind) but I think it will be interesting, at least to a few. I don't see it having a lot of impact on the average rag-chewer but then, what do I really know? I am reminded of Heinrich Hertz's response to the newspaper reporter when asked about the practical value of his proof of the existence of the electromagnetic waves proposed by James Clerk Maxwell. Hertz replied that he could think of no practical use whatsoever. Now if ever there was an amazingly wrong and shortsighted answer in history, this has to be near the top. Me? I plan to keep an open mind. ;-) -- Brian Lloyd, WB6RQN/J79BPL 3191 Western Dr. Cameron Park, CA 95682 [email protected] +1.767.617.1365 (Dominica) +1.916.877.5067 (USA) _______________________________________________ Flexedge mailing list [email protected] http://mail.flex-radio.biz/mailman/listinfo/flexedge_flex-radio.biz This is the FlexRadio Systems e-mail Reflector called FlexEdge. It is used for posting topics related to SDR software development and experimentalist who are using beta versions of the software. _______________________________________________ Flexedge mailing list [email protected] http://mail.flex-radio.biz/mailman/listinfo/flexedge_flex-radio.biz This is the FlexRadio Systems e-mail Reflector called FlexEdge. It is used for posting topics related to SDR software development and experimentalist who are using beta versions of the software.
