Tsys is essentially irrelevant for HF receivers, since Tambient is much, much higher (thousands of K) than even some really-poor RF engineering scenarios.
At HF, galactic background can be very high--1e4K or more. On 2016-03-30 10:30, Marcus Müller wrote: > Hi Daniel, > > haven't made experience with any of these upconverters; but: > > The really temperature-sensitive aspect of an upconverter is probably > the oscillator, not the mixer. So the trick might really be keeping > your upconverter in the same environment as your SDR receiver (assuming > both don't have overly well temperature-compensated or oven-controlled > oscillators), as that will just as much limit your frequency accuracy. > > Mixer circuits do exhibit conversion loss that tends to get worse with > rising temperature, but that'll not distort your signal much. > > The core question here is whether you'll deterioriate your system > performance if you keep your upverter far from your antenna; my guess is > that you'd have an LNA close to the antenna, anyway, so keeping the > upverter's oscillator warm and cozy near your SDR device won't be that > complicated, probably. > > That brings one down to the question whether you have the chance to use > the same oscillator for both your SDR device and the upconversion; that > way, you'd only have to worry about one device drifting under any > circumstance. Does your device give you the chance to couple out a clock > or maybe transmit a sine? > > Best regards, > Marcus > > On 30.03.2016 09:18, Daniel Pocock wrote: > >> Hi all, Has anybody been using any of the upconverters for SDR and has >> anybody made any comparison of them? I've seen some comments suggesting that >> many of the low cost models have poor thermal stability[1], has anybody seen >> problems with this in practice for receiving modes like SSB on amateur HF >> bands? If this is an issue, is anybody aware of alternative models that are >> more robust? Regards, Daniel 1. >> http://www.rtl-sdr.com/review-of-the-spyverter-upconverter/#comment-79953 >> [1] _______________________________________________ Discuss-gnuradio mailing >> list Discuss-gnuradio@gnu.org >> https://lists.gnu.org/mailman/listinfo/discuss-gnuradio [2] > > _______________________________________________ > Discuss-gnuradio mailing list > Discuss-gnuradio@gnu.org > https://lists.gnu.org/mailman/listinfo/discuss-gnuradio [2] Links: ------ [1] http://www.rtl-sdr.com/review-of-the-spyverter-upconverter/#comment-79953 [2] https://lists.gnu.org/mailman/listinfo/discuss-gnuradio
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