SunSDR2DX frequency calibration

Yes, I know that many of you do frequency calibration in one way or another for a living, playing with expensive professional toys. To you, frequency calibration is trivial, and you are probably smiling wondering – seriously, it this really necessary?

Well, it is. Ham radio is a hobby which naturally attracts radio professionals – but also newcomers from all other, non-technical fields. People without professional equipment, who would dare not to poke around with a screwdriver, messing with their brand-new radio.

When it comes to the frequency calibration of a modern SDR transceiver like SunSDR2DX, no expensive calibration equipment is needed at all. Neither is the knowledge of which trimmer cap to turn!

Here is a practical example. Using an IC-7700 as standard, the SunSDR was about 30Hz out of frequency. Not a big deal in CW or phone, and not that much of a deal even on digital modes where the entire FT8 band is 3Khz wide. But totally unacceptable for WSPR-2 where the band is 100Hz wide.

Adjustment: simply change the coefficient in the frequency correction setting. Which way to go: To add or deduct? Well, since I wanted to shift down (to be right onto the green bandwidth) the coefficient had to be increased. Couple of tries – and the signal was spot on. Value saved.

Of course, tuning into a WWV or any other time/frequency on-air carrier would do the trick too.

Here is the WWV 20.000MHz signal emitted from Fort Collins, Colorado.

(Tip: set the dial frequency to 19.999 plus 1KHz in audio spectrum of JTDX decoder.)

If you really like to be super calibrated, you can get your radio calibrated below 1Hz but that would make no sense unless the radio is physically kept at a very exact and consistent temperature.

Anyway, this is a non-technical tip to non-technical people. With SDR there is always something new to learn / play with. And if you stuff it up, simply load default value – and start again.