Frequency Error?

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jschall
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Frequency Error?

Post by jschall » Wed Dec 30, 2015 8:04 pm

I finally connected a longish wire as an indoor antenna, and was pleased to be able to pick up a known signal on 40 meters.

But I'm wondering if there is a frequency error of about 1.5 kHz from 7850.0 kHz, or am I just seeing a single sideband modulation, 1500 Hz audio?


Is there any way of correcting frequency errors with SDRPlay?

CHU Error.png
CHU Error.png (156.7 KiB) Viewed 8640 times
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Mont St-Hilaire, Québec

vsboost
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Re: Frequency Error?

Post by vsboost » Fri Jan 01, 2016 1:11 am

In the mixer section "Frequency Trim PPM" adjust that value until it is centred with a good known frequency, mine is set to 2.30 but they all vary.
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IW2NYX
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Re: Frequency Error?

Post by IW2NYX » Fri Jan 01, 2016 2:43 pm

1500Hz seems a lot, i suggest to switch on the carrier of another station, ie wwvh NIST (http://www.nist.gov/pml/div688/grp40/wwvh.cfm)

With -0.7ppm LO trim my SDRplay is frequency "spot on" on most reference stations.


Image
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jschall
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Re: Frequency Error?

Post by jschall » Fri Jan 01, 2016 6:33 pm

Thanks for pointing out the Frequency Trim function. I set mine to +5, and the CARRIER is bang on 7850 kHz. But the MODULATION is still off to the right. I looked it up on Wikipedia:


"CHU transmits 3 kW signals on 3330 and 14670 kHz, and a 10 kW signal on 7850 kHz.[2] These are nonstandard time signal channels; however, due to the prospect of interference with WWV and WWVH, the nonstandard frequencies are necessary. The signal is amplitude modulated, with the lower sideband suppressed (emission type H3E). The same information is carried on all three frequencies simultaneously including announcements every minute, alternating between English and French."
chu mod.png
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@IW2NYX: WWVH should be at 10.000 MHz, not 9.996 MHz. You'd better adjust your Frequency Trim :-)
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IW2NYX
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Re: Frequency Error?

Post by IW2NYX » Sat Jan 02, 2016 12:56 am

"@IW2NYX: WWVH should be at 10.000 MHz, not 9.996 MHz. You'd better adjust your Frequency Trim :-)"

Dear jschall,

that screenshot is about the time signal of Moscow Institute of Metrology for Time and Space, that transmits on following freqs :

4996 Khz
9996 Khz
14996 Khz

http://www.vniiftri.ru/index.php/en/

Here in EU comes quite strong with all three freqs.

I suggested NIST stations because i assumed that you are from North America region, am i right or wrong ?
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