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[Discuss-gnuradio] Re: FM stereo problem
From: |
Patrick Strasser |
Subject: |
[Discuss-gnuradio] Re: FM stereo problem |
Date: |
Wed, 26 Jan 2011 01:25:29 +0100 |
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Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.7.6) Gecko/20050602 Thunderbird/1.0.2 Mnenhy/0.7.2.0 |
schrieb Patrick Strasser on 2011-01-25 16:55:
> schrieb Bernardo Gonçalves am 2011-01-25 10:15:
>> Basically, the problem is that it works just as mono, not stereo...
> Second, I looked at your flowgraph. You shift the difference part from
> center frequency 38kHz to 0 with the Xlating FIR filter, and then use a
> complex-to-float block. This will not result in the positive
> frequencies. You'd rather have to filter out the negative frequencies
> with a Hilbert transformer, that is a special FIR filter keeping only
> positive frequencies, before converting to float again.
Sorry, I was wrong. You did the low-pass filtering, that was already right.
But two other things I did notice:
1) The difference signal, which is shifted down from 38kHz is several
10dB lower than the sum signal. With different gains I got something
more stereo-like.
2) The sum signal is faster than the difference signal. In the
diff-signal path you have more blocks that are processed. Some delay
(delay block) could maybe fix this problem, but I did not get the right
value at a quick try.
Patrick
--
Engineers motto: cheap, good, fast: choose any two
Patrick Strasser <patrick dot strasser at tugraz dot at>
Student of Telematik, Techn. University Graz, Austria