What's the settling time after new frequency set to dongle?

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Nikos Balkanas nikos.balkanas at eyeonix.com
Tue Jan 14 16:47:27 UTC 2014


On Tue, Jan 14, 2014 at 5:50 PM, <steve at steve-m.de> wrote:

> Hi,
>
>
> On 2014-01-14 15:23, Jiao Xianjun wrote:
>
>> Is there any information or hint on the settling time after new
>> frequency set to dongle?
>>
>
> That depends a bit on the tuner and the sample FIFO of the RTL2832,
> but you need to drop a few buffers, as the PLL of the tuner takes
> some time to lock and stabilize.
>
> Sample FiFO should be full at all times in a DVB-T. I have never seen it
empty due to interfernce, noise, etc.

>
>  Can I immediately read samples after new frequency is set by
>> rtlsdr_set_center_freq? If so, will the samples quality be degraded?
>>
>
> Kyle Keen did some experiments for his scanning application
> (rtl_power), and he settled for waiting a few milliseconds and
> flushing the buffer to get optimal results. See here:
>
> http://cgit.osmocom.org/rtl-sdr/tree/src/rtl_power.c#n626
>
> Regards,
> Steve
>
> That's a little too long, making large spectrum tuners inoperable. In my
scanner I use a read immediately after the frequency
set without any problems. Of course I cannot vouch for correct frequency,
but I have noticed that the frequency doesn't drift
appreciably when resetting frequency and locking to a band.

BR,
Nikos
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