Re: [Discuss-gnuradio] R820T frequency tuning issue

[Marcus D. Leech]

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 
> gnuradio-companion
> 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).
>
> JM
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.