Re: [Discuss-gnuradio] fft display frequency spotting

[Chuck Swiger]

At 05:01 PM 9/26/2005 -0300, you wrote:
> Hello everybody
> I would like to know how I can get a frequency
> precision with the fft_sink.
> If anybody can help me, I would like to receive any
> example with this.
> I saw this link
> http://lists.gnu.org/archive/html/discuss-gnuradio/2005-08/msg00019.html
> but when I implemented in the mc4020_fft.py, I had
> problems.

Rosciano - here is a quick hack of the above into usrp_fft.py  (I do not have
a mc4020, but this works with a usrp)  and only works in certain conditions

1) you do not resize the window and
2) you use the default decimation

To change size or decimation you must change some scaling and offset
numbers in the Mouse() function.   I've made notes of additions with
# (CS).

http://webpages.charter.net/cswiger/usrp_fft_mouse.py

If one could make the display fixed size (I tried putting size=(320,480) in 
the fft
statement but it didn't fix the size)  and factor the decimation into the 
offset
and scale factors it would be more auto-magic.  I tried, as Eric suggested
to get into plot.py and use find_closet_point() but didn't have any luck. 
In fact,
we don't actually want the *closest* point, just the X position in terms of 
the
frequency scale ;)

Being able to get an accurate frequency reading is a desirable feature, 
this kludge
might do untill someone does it right.

--Chuck