Re: [Discuss-gnuradio] Really low sample rates for gr_sig_source_x()

[Tom Rondeau]

On Sun, May 9, 2010 at 11:33 PM, Eric Blossom <address@hidden> wrote:
> On Sat, May 08, 2010 at 06:13:15PM -0400, Marcus D. Leech wrote:
>> It looks like when you set low sample rates (say below 1KHz), the NCO
>> code doesn't seem to work right,
>>   *never* putting out samples.
>>
>> I haven't done exhaustive testing.
>>
>> This was prompted by Bill Pretty's issue with his flow-graph that uses a
>> triangle or sawtooth generator,
>>   at low sample rates (2Hz) and low Fc (a fraction of a Hz) to drive the
>> tuning variable going back into
>>   the USRP.
>>
>> I tested the graph he gave, and after making a few fixes, observed that
>> the signal source appeared to be
>>   never producing any output.  Hmmmm.
>>
>> So, I did up my own flow-graph, consisting of a signal source, a
>> throttle, and a number sink and scope.
>>   It only started to work when I cranked the sample rate up to about
>> 1KHz on the signal source.
>>
>> Any ideas?
>
> Does it work without the throttle?
>
> Eric


I just tested it in GR with sig_source -> throttle -> scope sink.

I set the sample rate to 10 and the frequency of the signal to 1. It
took a while, but it eventually plotted output. I then used the 10 as
the sample rate for the signal source and 10k for the rate of the
throttle and it worked with results coming in much faster.

I think it's working as it should.

Tom