If you're comparing real time (system clock) to your sample stream,
you'll get jitter, not drift, using a throttle. Throttle maintains a
sample rate over time, but operates on blocks, and also is running under
a non-realtime operating system.
If you're talking about drift between the clock on your receiver and the
real world, that's normal and you have to find ways to deal with it.
- Jeff
On 10/08/2014 07:33 AM, Carlos Alberto Ruiz Naranjo wrote:
Yes, it is not a real time clock. This "clock" tracks the current time
of the signal in GNURadio.clock2 and clock1 have a drift because the
number of counted samples are different.
For example, if it pass 10230000 samples the delay block is entering the
delay in signal time = 1 second.
1 second in the real world (later I replay the signal with a USRP).
2014-10-08 13:18 GMT+02:00 Martin Braun <martin.br...@ettus.com
<mailto:martin.br...@ettus.com>>:
If you don't have hardware involved, you have no 'clock'. And as such,
it can't drift.
M
On 10/08/2014 12:29 PM, Carlos Alberto Ruiz Naranjo wrote:
> Sorry, I have explained bad: S
> I have the signal saved in a file and 10230000 samples are one second
> (in the real world).
>
> In the first graph I have two clocks (counters samples). When passing
> 102300 samples it increase0.01 seconds.
> In the first watchthis time controls the position of the
satellite and
> hisdelay in this time. It allows to know what signal time is
passing in
> the delay block.
>
>
> But I have a problem: clock 2 (a test clock) and clock 1 haven't the
> same time; it has a drift.
>
>
> Then, I must use clock 2 (
> count the samples in the delay block output, not input). But it creates
> a loop.
>
>
>
> 2014-10-08 12:07 GMT+02:00 Marcus Müller <marcus.muel...@ettus.com
<mailto:marcus.muel...@ettus.com>
> <mailto:marcus.muel...@ettus.com <mailto:marcus.muel...@ettus.com>>>:
>
> Hello Carlos,
> On 08.10.2014 09:10, Carlos Alberto Ruiz Naranjo wrote:
> > I generate the signal from a file (10230000 samples/s) to a file. My
> > sampling clock drifts significantly :S
> No. Unless I misunderstood you, you have a big misconception:
> "sampling clock" is *not* the rate at which your samples pass through
> your processing chain (ie. GNU Radio). It is the time base at which
they
> are measured, or simulated to, mathematically.
> The device/software that actually captures the samples and saves them
> has a fixed clock. If that clock changes too much a) compensate that
in
> software, if possible or b) get a better device.
> This is digital signal processing. Real world time has *no* meaning
> here, everything is measured relative to the interval between two
> sampling times. You can process the signal as fast or slow as you want
> to (as long as that doesn't lead to things like overflows), and
nothing
> in the processing chain should care.
> >
> > - Picture one: Counter Clock 2 is correct but Counter Clock 1 no.
> > Then I should use the second configuration, but it is not allowed
because I
> > have a loop, right?
> I don't understand your graph, sorry :(
>
> Greetings,
> Marcus
>
>
>
>
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