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*Subject*: [Linrad] Re: Update on SDR-IQ + Linrad + MAP65*From*: Joe Taylor <Princeton.EDU; joe@xxxxxxxxxxxxxxxx>*Date*: Thu, 13 Nov 2008 23:07:11 -0500

Hi Ed, Many thanks for your note! I'll let you know when there's something ready to test. You should be able to run it on a single (fast) computer. Let's be sure to work on 2m this weekend! If you call CQ, I'll find you... -- Joe, K1JT Edward Cole wrote: > At 07:54 AM 11/13/2008, you wrote: > >> Yesterday I spent some time playing with an SDR-IQ (from >> RFSpace) on both HF and 2m EME. It is an impressive little >> box: very simple, it just does what it is supposed to do. >> It works fine with Linrad, as well as with the SpectraVue >> software by AE4JY. Running the SDR-IQ under Linrad, I found >> that 2m JT65 EME signals are easy to see on the waterfall. >> I'm sure that none of this will surprise any reader of this >> list who has already gained some experience with the SDR-IQ. >> >> I have worked out, on paper, a scheme that should allow >> MAP65 to work with an unmodified SDR-IQ running under >> Linrad, while minimizing necessary changes to the MAP65 >> program code. The scheme involves choosing suitable >> decimation parameters CIC2, CIC5, and RCF for the SDR-IQ >> (these are parameters you can set from within Linrad) and >> suitable lengths for the FFTs used in MAP65. >> >> For your interest, here's a table showing some parameter >> values in the present MAP65 (used with 96 kHz soundcard >> input) and in the proposed "MAP65-IQ" as it would be >> configured for the SDR-IQ: >> >> Parameter Soundcard SDR-IQ >> (MAP65) (MAP65-IQ) >> ----------------------------------------------------------- >> f0 RF sample rate (Hz) - 66,666,667 >> nd Decimation factor - 714 >> CIC2 CIC5 RCF - 7 17 6 >> f1 Baseband sample rate (Hz) 96000.0 93370.68 >> n0 FFT for sync search 32768 32768 >> w0 Bin width (Hz) 2.930 2.849 >> n1 FFT full transmission 5,376,000 5,378,240 >> Factors 7 5^3 3 2^11 7^5 5 2^6 >> t1 Time for complex FFT (s) 1.39 0.66 >> n2 Inverse FFT, each signal 77175 79380 >> Factors 7^3 5^2 3^2 7^2 5 3^4 2^2 >> t2 Time for complex FFT (s) 0.00607 0.00324 >> f2 Final sample rate (Hz) 1378.125 1378.102 >> >> Both systems provide usable bandwidths of 85-90 kHz -- more >> than enough to cover the relevant JT65 sub-bands for EME on >> 144, 432, and 1296 MHz. >> >> For each one-minute block of received data, MAP65 does 279 >> FFTs of length 32768 to get power spectra for all required >> half-JT65-symbol intervals. The resulting (32768 x 279) 2-D >> spectra are searched for JT65 sync signals and shorthand >> messages. The slightly different bin widths w0 in standard >> MAP65 and MAP65-IQ can be easily accommodated in the software. >> >> MAP65 then does an FFT over the full span of received data >> (about 52 seconds), with the complex data arrays zero-padded >> to length n1. Inverse FFTs of length n2 are then done with >> data around each frequency where a sync tone was found. >> This process yields downsampled complex data with effective >> sample rate f2=f1*n2/n1. As you can see in the table above, >> the parameter values given in the MAP65-IQ column yield an >> f2 with almost the same value as in the present version of >> MAP65. This condition is desirable because it requires a >> minimum of changes to the remaining downstream program code. >> >> As shown in the table for both MAP65 and MAP65-IQ, the >> selected values of n1 and n2 can be factored into a number >> of small primes. This condition is necessary for the >> efficient computation of FFTs. The FFT lengths for MAP65-IQ >> are actually "better" than those in the present MAP65, in >> that their FFTs run nearly twice as fast (see values of t1, >> t2 in the table). Of course, since MAP65 operates on >> dual-polarization data while MAP65-IQ processes a single >> polarization, MAP65-IQ already has less than half the >> computational load. MAP65 is fast enough on a modern >> computer. MAP65-IQ will be several times faster. >> >> MAP65-IQ should be an excellent tool for anyone using JT65 >> with a single-polarization (or switchable polarization) >> receiving system on 144 and 432 MHz. It should also make a >> superb JT65 system for 1296 MHz, where circular-polarization >> EME is the norm. >> >> I hope to find time to work on code for MAP65-IQ over the >> next few months. >> >> -- 73, Joe, K1JT >> > > Joe, > > Thanks very much for working on this. I will try this out with my > SDR-IQ and Linrad. I guess you are still running Linrad on a > separate computer from MAP65 (or not). I have not gotten into the > interfacing of Linrad to MAP65 since I was waiting for the SDR-IQ solution. > > Is there things to do to make Linrad talk to MAP65 in the above > procedure? I can also run Linrad on the same 2.33 GHz computer If I > can find out how they port together. > > > *********************************************************** > 73, Ed - KL7UW BP40iq, 6m - 3cm > 144-EME: FT-847, mgf-1801, 4x-xp20, 185w > 1296-EME: DEMI-Xvtr, 0.30 dBNF, 4.9m dish, 60W (not QRV, yet) > http://www.kl7uw.com AK VHF-Up Group > NA Rep. for DUBUS: dubususa@xxxxxxxxxxx > *********************************************************** > > > > --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "Linrad" group. To post to this group, send email to linrad@xxxxxxxxxxxxxxxx To unsubscribe from this group, send email to linrad+unsubscribe@xxxxxxxxxxxxxxxx For more options, visit this group at http://groups.google.com/group/linrad?hl=en -~----------~----~----~----~------~----~------~--~---LINRADDARNIL