UHF 3.5kHz Off Frequency How to Adjust?

[woodpecker]

Just received my sdrplay and its 3.5kHz off frequency at UHF, I'm using SDR-Console 2.3 v2381 and cannot see any way to calibrate it?

I have various other SDRs, an Airspy and some Nooelecs with TXCOs and none need any calibration at all.

Any advice please?

[Tech_Support]

Hello Woodpecker,
There is currently no direct method of applying a PPM correction in SDR Console V2.3, although it is our understanding that this is a feature that will ultimately be added to V3. We plan to incorporate PPM correction in our next release of the API making it easier for S/W developers to add the feature to their packages by simply making a function call and passing a parameter.
On the other hand, if you use HDSDR, there is currently a PPM correction via our ExtIO plugin interface. However, if you prefer to stick with SDR Console, apparently one users has worked out a method by which is can be achieved in the current versions of SDR Console. We have not verified this ourselves, but it might be worth you trying

Quote:

viewtopic.php?f=7&t=510&p=1910&hilit=correction#p1910

I have found this work around for now if you use HRD and DM780

1. Add your transmitter as the external radio.
2. Tune to WWV and then use the Offset in the external radio setting to find the correct setting to center the frequency. Record this number. In my case it is -23
3. Reset back to 0hz.
4. In DM780 goto "Program Options" -> "QSO" -> "General Tab" -> "Transmit Offset" Adjust this number to the negative of the number in #2. In my case it is 23.

Have a PSk31 contact and tweak the setting. In the end I use 25 and it works fine.

I hope this helps until there is a PPM correction.

End of Quote

I hope this helps

Sincerely

SDRplay Tech_Support

[woodpecker]

I can't seem to find any offset in sdr-console to set looking at those notes.

I've got to say I expected better from the sdrplay, now I realise you are using +/- 10ppm crystal for the oscillator (which doesn't seem to appear in any specs of the unit) I can see the problem, surely this isn't a good design in a receiver branded for up to 2GHz operation.

It also suffers some pretty chronic overload even with an FM broadcast band filter and a variable attenuator tweaked for optimum receive, I was hoping to get performance similar to the Airspy but with HF included, its a long way behind from my initial tests.

[13dka]

The workaround mentioned above seems to apply to transmitting PSK31 with Hamradio Deluxe only, describing how to set an offset in that software which was measured in SDR Console before?

I can only recommend using SDR# v1367 or HDSDR for VHF/UHF for the simple reason that the SDRPlay ExtIO.DLL has an oscillator trim feature. That doesn't really help with the problem that there are no signals above the FM band that could serve as a reliable calibration signal though, and even FM transmitters are not always well-calibrated nowadays (I'm getting a few kHz of variation here on different stations on the FM band, so I have to rely on averaging those that were paid with my tax money and still employ some engineers, and do not blast music into the air 24/7).

As for the FM images, they are mostly a problem between 250 and 420 MHz, so for the time being (and I guess for the RSP1 that will be a "forever", since it's a inherent "feature" of the design) that range is only usable on frequencies that don't have an image on them. But I'm surprised that the FM band stop filter does not help, what type/design/make/model are you using? I'm asking so I'll buy something different in case I want to try a filter myself.