Clocks on SDRs
Andrew Thornett
Marko Cebokli
Most natural sources are broadband, so unless you are doing inerferometry, for total power radiometry, clock quality is not important, anything will do.
For hydrogen line and similar work, a TCXO will be a excellent, allowing Doppler analysis etc. Just for detecting it, a plain crystal oscillator, as found in most SDRs will be enough.
It would be more important for narrow line sources like masers, especially if you work at 12 or 21 Ghz, you will need a better frequency reference, important for the down conversion, like at least a PLL LNB, if possible, hooked to a good reference (TCXO, OCXO).
Also, if you would want to study pulsar timing, you would need an even better clock, like GPS controlled.
Just for detecting pulsars, clock quality won't be that important.
So I would say, if you want to start with hydrogen line, do not agonize much about the clock, there are other things, like antenna and LNA, which will be more important in the beginning. Later, as you build up your system, you can improve your clocks as you go.
Marko Cebokli
21.06.2026 14:46, je 'Andrew Thornett' via Society of Amateur Radio Astronomers napisal
I have noticed recently discussions about quality of clocks on SDRs and this also came up in recent Monday evening practical RA meetings.When and for what is it important to have a good quality clock on your SDR?Andy
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Marcus D. Leech
Just for detecting pulsars, clock quality won't be that important.
That includes better clocks, because otherwise, the pulses tend to get smeared down into the noise as you're doing synchronous detection. Having at least a
TCXO helps.
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Andrew Thornett
Sent: Sunday, 21 June 2026 15:14:42
To: sara...@googlegroups.com <sara...@googlegroups.com>
Subject: Re: [SARA] Clocks on SDRs
Marcus D. Leech
I hear thay Airspy is pretty impressive wirh its clock, is that right?
At what point does the clock in am Ettus B210 become relevant i.e. at what what will an amateur even notice the difference using the one device over another?
o wider tuning range compared to AirSpy R2 (50MHz - 6GHz)
o higher sample rates (up to 56Msps)
o Dual mutually-coherent channels (makes interferometry pretty straightforward)
o keeps all that pesky cash out of your bank account or wallet :)
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