What's the settling time after new frequency set to dongle?
Hi, Is there any information or hint on the settling time after new frequency set to dongle? Or is there any method to read information from dongle to see if all things get stable? Can I immediately read samples after new frequency is set by rtlsdr_set_center_freq? If so, will the samples quality be degraded? Thanks! BR Jiao Xianjun
Yes, you can read traffic immediately after setting new frequency. No settling needed ;-) Just make sure your read buffer is at least 512 B or libusb_bulk_transfer will fail :-( BR, Nikos On Tue, Jan 14, 2014 at 4:23 PM, Jiao Xianjun <putaoshu@gmail.com> wrote:
Hi,
Is there any information or hint on the settling time after new frequency set to dongle?
Or is there any method to read information from dongle to see if all things get stable?
Can I immediately read samples after new frequency is set by rtlsdr_set_center_freq? If so, will the samples quality be degraded?
Thanks!
BR
Jiao Xianjun
Settling time should be wery small (up to few tenths of ms or even faster), internal buffering in dongle is also small. You should drop few thousand samles to be sure all is fine. This results are from observation, not from measurement, can someone provide hard data? Dne 14.1.2014 15:23, Jiao Xianjun napsal(a):
Hi,
Is there any information or hint on the settling time after new frequency set to dongle?
Or is there any method to read information from dongle to see if all things get stable?
Can I immediately read samples after new frequency is set by rtlsdr_set_center_freq? If so, will the samples quality be degraded?
Thanks!
BR
Jiao Xianjun
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.
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
On Tue, Jan 14, 2014 at 5:50 PM, <steve@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
We forgot the most important parameter. The frequency "jump". If the frequency change is large, i.e. from 10 Khz to 1 Ghz, then of course it will take longer for the tuner to equilibrate. In my scanner, when I approach a target I take 10 baby steps of 2 Khz each to zero in. Drift is negligible. I tried using the 5000 us in my scanner, and the results were the same as without it, except for the delay of an additional 50 s. I promptly removed it. The way I see it, tuner needs some time to settle in a new frequency, but there is no fixed delay. It is situation specific and depends highly on the amount of frequency change. HTH, Nikos On Tue, Jan 14, 2014 at 6:47 PM, Nikos Balkanas <nikos.balkanas@eyeonix.com>wrote:
On Tue, Jan 14, 2014 at 5:50 PM, <steve@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
participants (4)
-
Jiao Xianjun -
Jiří Pinkava -
Nikos Balkanas -
steve＠steve-m.de