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From: | Marcus Leech |
Subject: | Re: [Discuss-gnuradio] Carrier offset on DBSRX. |
Date: | Tue, 27 Mar 2007 21:40:30 -0400 |
User-agent: | Thunderbird 1.5.0.10 (X11/20070221) |
Trond Danielsen wrote:
I use the DBS_RX for radio astronomy, and I use a narrowband calibration signal (not from a precision source, but within a few Khz). That signal shows up in my FFT display within a few Khz of where it should be. I never see any errors as large as 500Khz, that's for sure, and I've used 3 different DBS_RX boards over the last coupleOkay, I think I understand. But still, when inspecting the signal with ursp_fft.py, the signal is not at baseband, but offset by approx. 500kHz
of years.Also, 21cm emissions from the galactic plane are usually within 200Khz of 1420.4058Mhz, and that's where they show up, so I'm reluctant to believe that in *general* observed frequencies can be off by as much as 500Khz.
Something else is wrong.
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