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Re: [Discuss-gnuradio] R820T frequency tuning issue

From: Marcus D. Leech
Subject: Re: [Discuss-gnuradio] R820T frequency tuning issue
Date: Sat, 28 Mar 2015 10:47:48 -0400
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.2.0

On 03/28/2015 10:23 AM, address@hidden wrote:
As a quick followup to my previous post, I confirm that the R820T is well 
suited for GPS
signal decoding. I was not expecting the huge frequency offset (> 100 kHz at 
1.57 GHz) and
was not searching far enough from the expected carrier frequency during the 
acquisition phase.
However these results were acquired by runnig rtl_sdr -s ... -f ... while 
running gr-osmosdr is unable to lock at 1.57 GHz and barely locks (for a few 
seconds !) at
1.56 GHz. I have analyzed the various version of librtlsdr (used by rtl_sdr and 
by gr-oscmocom)
as well as the set_frequency functions and am unable to track any difference 
between the two
codes (so far).


The R820T is generally flaky above about 1550MHz. Maybe in your rtl_sdr tests, you just got lucky.

gr-osmosdr uses the *SAME* underlying library as rtl_sdr, and at the level of Gnu Radio, all of the low-level stuff like
  "is the PLL locked" is utterly invisible to the Gnu Radio layer.

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