Re: [Discuss-gnuradio] Squelch developments

[Norvald H. Ryeng]

On Sat, Jun 17, 2006 at 12:58:12PM -0700, Johnathan Corgan wrote:
> I am creating a new squelch block:
> 
> gr.pwr_squelch_cc

[...]

> As far as naming goes, calling this pwr_squelch_xx is anticipation of
> other squelch type blocks:
> 
> gr.pwr_squelch_ff - same as pwr_squelch_cc but for audio, like a "VOX"
> switch
> 
> gr.ctcss_squelch_ff - gate or zero audio output when a ctcss tone is not
> present
> 
> gr.noise_squelch_ff - gate or zero audio output when noise is present (I
> think this what standard_squelch is detecting)
> 
> gr.dcs_squelch_ff - gate or zero audio output when digitally coded
> squelch is not present
> 
> etc.

Great!

I would definitely want to see those. In some cases it is nice to have a
recording of all communications without all the noise in between. I've
been doing this for some time using the "listener" program
(http://www.vanheusden.com/listener/) and input through the soundcard
from a radio, but with that approach I need one radio and soundcard for
each channel. I've been thinking of using gnuradio and a USRP to record
all channels simultaneously, and that would require some of these
blocks.

There is one nice feature in listener that I would really like to see in
these blocks: the ability to start output a few seconds (or rather a
given number of samples) before the squelch opens and keep it open for a
while after the signal disappears. This corrects for bad tone modulation
and weak signals that otherwise would make the squelch block cut the
transmission into several chunks. Also, for my purposes, it makes the
squelch stay open during the "think time" between request and reply.

Listener also has parameters that set a minimum and maximum time for the
squelch to stay open. The last one could easily be implemented as a
separate block, but the first one has to be implemented in the squelch
block. I'm not sure how useful these options are (I'm not using them),
but implementing them should be fairly straight-forward.

> (Not that I'm signing up to write all these!)

Me neither. I'm new to gnuradio (hi to the list, by the way -- I've been
lurking for a few months) and still at the getting-things-to-work stage.
I hope to spend some time this summer learning more about gnuradio, but
I'm still far from writing my own blocks.

Regards,

Norvald H. Ryeng, LA6YKA