Forum: GNU Radio preemph time constant

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Dimitris S. (Guest)
on 2009-02-27 20:18
(Received via mailing list)
the fm_preemph and fm_deemph functions in blks2impl/fm_emph.py take
the argument tau (time constant), which is 75μsec for the US and
50μsec for Europe and the rest of the world. If now tau is given, the
75 is assumed by default...

Now, the wfm_rcv and wfm_rcv_pll of blks2 don't take a tau parameter
and subsequently call the fm_deemph without tau, meaning
blks2.wfm_rcv{_pll} defaults to the US modus operandi, and there's no
way to tell it to do otherwise...

Is it ok to add this (optional) parameter and send a patch to
removed_email_address@domain.invalid, or is there some risk of breaking stuff?

By the way, I sent another (trivial) patch on Feb 5 to
removed_email_address@domain.invalid, adding documentation to two blocks, which
hasn't made it into the trunk yet. Is there anything I should do,
other than being patient, obviously :-)

Also, the fm_preemph function doesn't complete the right answer (and
is stated so with a FIXME), I will try to fix it and send you another
patch soon

Dimitris S.
"If you think you're too small to make a difference, try sleeping with
a mosquito!" - Amnesty International
John Ackermann N8UR (Guest)
on 2009-02-27 20:34
(Received via mailing list)
I don't recall the details, but I believe that (at least in the US) the
preemph for WBFM (ie, FM broadcast) is different from that for NBFM (ie,
2-way) -- 250usec comes to mind.

John
----
Josh B. (Guest)
on 2009-02-27 20:48
(Received via mailing list)
This seems like a job for ~/.gnuradio/config.conf
Johnathan C. (Guest)
on 2009-03-02 23:25
(Received via mailing list)
On Fri, Feb 27, 2009 at 10:15 AM, Dimitris S.
<removed_email_address@domain.invalid> wrote:

> Is it ok to add this (optional) parameter and send a patch to
> removed_email_address@domain.invalid, or is there some risk of breaking stuff?

Go ahead and send this to the patch-gnuradio list, we'll put it in the
review queue.

Johnathan
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