Re: [Discuss-gnuradio] Up Conversion Weirdness

[Thomas Schmid]

Hi Tom

On 10/25/06, Tom Rondeau <address@hidden> wrote:
> First, I assume you meant the second to last line to read:
> > self.connect(self.multiplicator, self.amp, self.u)

No, this is exactly the problem. Even if I directly hook up the
interpolator1 to the USRP, it doesn't work. So, hooking up something
to a different path in the flow graph results in the problem. But I
also tried it this way with the same effect.

> What is the sampling rate at this point in the flow graph, and what is the
> frequency of the sine wave? I'm just trying to make sure you're not
> upconverting beyond the first Nyquist zone. For this app, you're still
> looking at the upconverted signal as baseband, so your sampling rate must be
> at least 2x(f_sin + signal BW). I assume that's what the interpolator is
> doing, but just making sure.

Sorry, I forgot to mention that.

The frequency of the sine wave is around 500kHz. The Sampling rate of
the sine wave is 4MS/s and the signal bandwidth is around 300kHz. So
yes, the interpolator interpolates the signal to the required 4MS/s.

> What's the file look like when you plot it locally?

After doing some more tests, I found out the following. Instead of
sending it to the USRP, i sent the data to a second file sink. The
data looks fine, but it is way too short. In the case where it works,
the filesize is around 80MBi for 100 sent packets. In the second case,
the file is only about 4MBi and contains only the first 9 packets
instead of 100 (tested by running it through the decoder).

Thomas