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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 _______________________________________________ Discuss-gnuradio mailing list address@hidden https://lists.gnu.org/mailman/listinfo/discuss-gnuradio
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