[OZAPRS] TNC

[James Cameron]

On Wed, Jan 13, 2010 at 10:05:10AM +1100, Norm, VK3XCI wrote:
> I've been using a 2M Quansheng for APRS for some time and I'm well
> aware of the Sleep problem. I've just never quantified it so thank you
> James.

I've a unit that when the batteries are fully charged or if you give it
a DC input above a certain point ... clicks the speaker at the wake up
point.  Recording that sound gives an accurate measure.  Also used a CRO
at a slow scan rate, measuring the current draw of the radio, while
varying DC input.

> The DC effect is a new one to me, but does explain some odd things.

Yes; if the combination of the received audio and the DC offset during
the first 25 mS causes the level to clip, the FSK demod is troubled.

> Obviously transmitting also wakes up the rx.

Yes, it does.  That's another way to solve it on a private APRS link;
send very frequently.  Antisocial in other contexts.

> BTW, defeating the sleep mode with the monitor switch really kills the
> battery life on rx as it runs the receiver and audio.

Indeed it does.  I used an external supply to make that less of a worry.

> Wonder if there's a software/firmware way of defeating it and still
> having a squelch

Periodic very short closures of the monitor switch, perhaps.

Other than that, I've found no useful programming or firmware hacks.
;-)  I wish for an open firmware radio.

-- 
James Cameron
http://quozl.linux.org.au/