Re: [Discuss-gnuradio] comparing SDR upconverters, thermal stability

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 Discuss-gnuradio@gnu.org https://lists.gnu.org/mailman/listinfo/discuss-gnuradio

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