[Top][All Lists]

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: [Discuss-gnuradio] preemph time constant

From: John Ackermann N8UR
Subject: Re: [Discuss-gnuradio] preemph time constant
Date: Fri, 27 Feb 2009 13:32:46 -0500
User-agent: Thunderbird (Windows/20081209)

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.


Dimitris Symeonidis wrote:
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
address@hidden, or is there some risk of breaking stuff?

By the way, I sent another (trivial) patch on Feb 5 to
address@hidden, 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 Symeonidis
"If you think you're too small to make a difference, try sleeping with
a mosquito!" - Amnesty International

Discuss-gnuradio mailing list

reply via email to

[Prev in Thread] Current Thread [Next in Thread]