RSP2 Frequency is Incorrect - Why?

[ultravista]

I just bought a 2nd hand RSP 2 on eBay (from a ham).

With SDRUno, SDR#, and HDSDR, the frequency is off a bit compared to a known signal. For example, in SDRuno, my local Las Vegas NOAA frequency is 162.555.000 but the applications above don't 'center' with the signal @ 162.555.000 but 162.555.200 instead.

By 'center', I mean the peak of the signal in the application.

The issue is similar across every application, so I know it's not an offset problem with a single application.

For the record, my RTL-SDR v1.3 dongle tunes exactly on the right frequency.

What would cause the RSP 2 to tune incorrectly?

What are the last three digits and the frequency above, hertz? In other words, the RSP is off by 200 hertz?

 

[slicerwizard]

No, it's off by about one part per million. Not exactly a big deal or unexpected with these devices.

 

[SCPD]

NOAA is 162.550 so *if* the OP *is* tuned to 162.5552 - that's more like 32 ppm.

 

[jonwienke]

PLL-controlled radios have a reference crystal they use as a frequency reference. If that reference crystal is off-frequency, then every frequency generated by the PLL will be wrong by the same percentage.

The RTL-SDR dongle uses an extra-accurate TXCO frequency reference that is accurate to within one part per million, so the PPM adjustment in SDR# or other programs usually best left at zero.

The RSP2, evidently not so much. It could be why you got a deal on it.

 

[mbott]

I just bought a 2nd hand RSP 2 on eBay (from a ham).

With SDRUno, SDR#, and HDSDR, the frequency is off a bit compared to a known signal. For example, in SDRuno, my local Las Vegas NOAA frequency is 162.555.000 but the applications above don't 'center' with the signal @ 162.555.000 but 162.555.200 instead.

<snip>

My local NWS is not exactly on the freq. they claim to be operating on. What is the difference on any of the WWV or CHU frequencies?

--
Mike

 

[ultravista]

PLL-controlled radios have a reference crystal they use as a frequency reference. If that reference crystal is off-frequency, then every frequency generated by the PLL will be wrong by the same percentage.

The RTL-SDR dongle uses an extra-accurate TXCO frequency reference that is accurate to within one part per million, so the PPM adjustment in SDR# or other programs usually best left at zero.

The RSP2, evidently not so much. It could be why you got a deal on it.

I am surprised that a much more expensive piece of equipment is off-frequency compared to the $25 RTL-SDR. Yes NOAA 162.555.000 tunes in precisely at 162.555.200.

 

[Your_account]

The RTL-SDR dongle uses an extra-accurate TXCO frequency reference that is accurate to within one part per million, so the PPM adjustment in SDR# or other programs usually best left at zero.

my dongle are between +/- 60ppm!!!