Re: [Discuss-gnuradio] More Swept FFT

[Marcus D. Leech]

On 05/03/2010 10:37 PM, William Pretty Security Inc wrote:

Ok.

So I combined the suggestions from Josh and Marcus:

 

Variables:

decim:                  Value:   8

samp_rate:         Value:   100e6/decim

tun_freq:            Value:   56e6+(tune*1e6)

tune:                     Value:   0

 

Signal Source:

Output type:      float

Sample Rate:     samp_rate

Waveform:         Triangle

Frequency:         .01

Amplitude:         1

Offest:                  0

 

Variable Sink:     tune

Type:                     Float

Decimation:        decim

Vec Length:        1

 

Here’s what happened:

The FFT Sink block controls work, but the center frequency doesn’t change.

Also the arrow between the Signal Source and the Variable Sink is grayed out and I don’t know why ??

 

 

I would set the sample rate of the triangle source to something closer to nyquist myself. Having
  it run at 12.5 SPS seems rather wasteful when you're trying to generate a sub-Hz signal.

You may need also to put in a throttle block right after the signal source, and have that throttle
  match the sample rate of the signal source.  I would suggest a sample rate of 1000Hz would be
  more than adequate to give you the resolution you need for  a sub-1Hz triangle wave.

-- 
Principal Investigator
Shirleys Bay Radio Astronomy Consortium
http://www.sbrac.org