Re: [Discuss-gnuradio] Why do I have a sampling rate limit of 33.333 Msps?

[Tom Rondeau]

On Wed, Oct 3, 2012 at 2:00 AM, LD Zhang <address@hidden> wrote:
> Hi Nick,
>
> Thanks for your helpful comments. I have followed up on this train of
> thought on specifying a frequency for the USRP. I guess the advantage is one
> can achieve the same level of over-sampling with lower sampling rate with
> this technique when one shifts closer to the frequency of interest. I gave
> it a try in the USRP and have the following observations:
>
> 1. The spectrum center essentially shifts to the specified frequency. No
> band pass filtering seems to be applied at all. My only concern is that this
> lack of band pass filtering may hinder dynamic range in certain cases but
> not a problem for now.

Yes, that's right. The daughterboards are designed to have a wide
range in frequency. If you are concerned about this issue, the idea is
that you will have to provide your own filtering (and probably
amplification) for a particular frequency band you are interested in.

> 2. I have kind of a logistic question. I am running the GRC file which
> directs the output to a file sink. Since I am doing different parameter
> studies of the system performance, I need to generate different files with
> different operating parameters. I don't know how to automatically dump
> parameters like samp rate, samp duration, center freq, BW, gain, etc., to
> the recorded file so that analysis can be somewhat automated. Maybe this is
> a question that should be asked under a different subject heading.

There is nothing that really does that right now. It's been on the
to-do list for a while, but the issue is doing it right. There's a lot
of history about how to store metadata in sample files, and we haven't
wanted to lock ourselves into a way of doing this without using
something that people would find the most useful.

Tom


> Thanks,
>
> LD