Ok, i’ve attached very simple grc chart
with slider you can change the frequency, two waterfalls shows spectrums
before and after xlating.
So i had test it in apco25 env and took apco signals as a reference. So
when i saw signal e.g. at 451.378 MHz and tuned to it i saw no signal
after
xlating nevertheless it was the same time on waterfall before xlating.
You can test this chart with you radio environment.
Then i testing the same logic with gr 3.6 (code is not compatible i have
to
redraw it…) and here it is! xlating worked like a charm.
redraw it…) and here it is! xlating worked like a charm.
Try reversing the sign of the center frequency value for the xlating
filter. I’ve been using this block for some tests of my own this week
and it’s working as expected.
Tom
Specify what you configured, what the expected outcome was and what
Research Associate
National Laboratory of the Helmholtz Association [email protected] Discuss-gnuradio Info Page
Hi Anton,
it is really hard to capture apco25 signals in Germany.
Could you really open a ticket, attach a few captured samples saved
using a file sink,
and the 3.6 and 3.7 flowgraphs; or provide some kind of test case with
GNU Radio Signal sources
that simulate a signal. Be sure to attach screenshots of your waterfall
plots.
It is really hard to guess what goes wrong otherwise.
It’s not just you, I noticed this too. This change broke gr-atsc ( but I
fixed that ).
The problem is on line 80 of
gr-filter/lib/freq_xlating_fir_filter_XXX_impl.cc.t: the 2 was not
negative
in 3.6 but is now, i’m not sure why.
It’s not just you, I noticed this too. This change broke gr-atsc ( but I
fixed that ).
The problem is on line 80 of
gr-filter/lib/freq_xlating_fir_filter_XXX_impl.cc.t: the 2 was not
negative in 3.6 but is now, i’m not sure why.
Good catch, thanks.
The “old style” version of the block in gnuradio-core in 3.6.5.1 works
correctly. The “new style” version of the block in gr-filter in 3.6.5.1
has the sign change. When all the old-style blocks were removed for
3.7, this of course left only the changed one.
Since it was Tom who did the conversion on that block, I’ll wait until
he chimes in on whether his change was an accident or intentional.
The “old style” version of the block in gnuradio-core in 3.6.5.1 works
correctly. The “new style” version of the block in gr-filter in 3.6.5.1
has the sign change. When all the old-style blocks were removed for
3.7, this of course left only the changed one.
Personally I always thought that the previous block (in 3.6) was
“weird” because the parameter was named “Center freq” but you in fact
had to give it the frequency shift you wanted. The new one behaves
more like I expect.
The “old style” version of the block in gnuradio-core in 3.6.5.1 works
correctly. The “new style” version of the block in gr-filter in 3.6.5.1
has the sign change. When all the old-style blocks were removed for
3.7, this of course left only the changed one.
Since it was Tom who did the conversion on that block, I’ll wait until
he chimes in on whether his change was an accident or intentional.
I’ll defer to those who know the code better than I, however I will note
that the fact that it was “reverse” (ie negative values went “up” in
frequency within the filter" confused me at first…
…But then I spoke to others that used other SDRs, and found that they
had the same behaviour. So I stuck a sign in front, and carried on,
believing it was some strange function of the way things worked deep
in SDR theory, and didn’t worry about it any more.
Would suggest that if others do it this way (ie negative values in the
FIR filter go up), it may be worth to keep that behaviour for
convention’s sake if there’s no better reason to change it