Benchmark tone

[shifty21]

What frequency can I tune to to set the oscillator on my USB dongle? I thought I had correctly adjusted it by tuning in to 470.309.000. I saw that on a YouTube video. However, it still seems that I'm off.


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[DaveNF2G]

Every one is slightly different. The correct way to calibrate is to use the ppm offset setting. You might need to adjust this setting slightly differently for various frequency ranges.

 

[shifty21]

Thanks for replying but that's my point. I'm in southswestern Ontario Canada. I need an absolute frequency by which to tune to to set the offset

 

[joeuser]

I used a control channel from my local P25p1 system. I suppose you could use an FM station with RDS or something?

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[KC8ESL]

+1 on the known CC of a P25 system.

NOAA WX radio is also a great source, though extremely wide.

 

[shifty21]

FM radio station is too wide I think. I found an amateur radio frequency in use and used that. The shipped antenna isn't good enough to pull in NOAA. Any suggestions there?


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[KC8ESL]

Where are you that you can't tune in a NOAA WX broadcast?
Do you have any other radios that support that same issue?

Find a $2 cookie sheet and use it as a ground plane for that little antenna.

 

[shifty21]

Sarnia, Ontario, Canada. I can get the NOAA on my Baofeng and FRS radios. Just not the RTL2832 dongle with included antenna


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[KC8ESL]

Well then... Canada, ok, so I suppose NOAA wouldn't be a very reliable source.

I think that ideally, a p25 cc would be the way to go. Narrow carrier, easy to hit on frequency.

 

[Token]

What frequency can I tune to to set the oscillator on my USB dongle? I thought I had correctly adjusted it by tuning in to 470.309.000. I saw that on a YouTube video. However, it still seems that I'm off.

What you used to calibrate was an ATSC Pilot tone (list of other usable pilot tone freqs seen here North American television frequencies - Wikipedia, the free encyclopedia ). Note that ATSC Pilot Tone standard is + and – 1 kHz, so the actual freq can be XXX.309000 to XXX.311000 MHz. If all you want is that level of accuracy then you can use tones from multiple TV channels to make sure each band segment is good to go.

T!

 

[shifty21]

Thanks folks

 

[nd5y]

You should not use ATSC pilot carriers for calibration unless you the exact frequency a particular TV station uses. The pilot carrier frequency can vary because there are several frequency offsets that can be used.
Refer to page 79 of http://www.atsc.org/cms/standards/a_54a_with_corr_1.pdf
and page 12 of http://www.atsc.org/cms/standards/a_64b.pdf

 

[joeuser]

Thanks folks

Good luck!

 

[slicerwizard]

You should let the dongle warm up by using it (not just leaving it plugged in) for ten minutes and then tune to a high frequency signal, like Spectrum Communication's control channel on 857.3125 - don't waste your time on a VHF weather channel. Don't know why some folks can't grok the concept of parts per million...

 

[KC8ESL]

Seriously? I "grok" the concept but if he has a crappy antenna attached, sometimes it (NOAA) is all you can hear/see on the spectrum.

Take what you can get and improve from there.