[aprssig] D700 Tip. Reading Mail

Wes Johnston, AI4PX wes at ai4px.com
Tue Jul 31 15:03:07 EDT 2007

Some radios do allow for a different pl for TX than RX, and in that case,
set the RX pl tone to 100 and the TX pl tone to anything but 100hz.


On 7/31/07, Robert Bruninga <bruninga at usna.edu> wrote:
> >>> How do we call CQ locally on APRS?
> >>
> >>Voice Alert.  Each of packet contains a 100 HZ tone which will
> >>be heard [by] all surrounding APRS also running Voice Alert.
> >
> > I never quite got this.   In order for this to work,
> > I'd need to run PL squelch, right?  So how, then,
> > would my APRS station be able to hear, say, the
> > local digi or WX station that *isn't* transmitting
> > a PL of 100?
> The D7 and D700 take their TNC data from the radio receiver in
> front of the CTCSS tone squelch.  The CTCSS tone squelch only
> silences the speaker in the D7 and D700.  This is why we can get
> dual use from the 144.39 APRS channel for both APRS data
> (without PL) and for the occasional human-to-human voice call
> with PL 100.
> Running Voice Alert in the mobile, is like adding another free
> radio channel in the APRS mobile.  This hidden-back-channel is
> for being able to make a voice call to such an operator on a
> guaranteed known voice calling channel that you know he is
> monitoring... Because you hear his (and only his) packet when he
> is in SIMPLEX range (about 1 to 3 miles)...
> It works!
> But the WORST killer of this function is HOME stations or 24/7
> parked cars that still TX their Voice Alert PL100 packets
> *without* an operator present.  This is very frustrating since
> other voice alert mobiles that might be passing by, hear these
> "CQ's" yet no one is listening in response.
> So remember, Voice Alert is a MOBILE-to-mobile system only.
> Home stations that TX it continuously can kill the golden goose
> due to QRM.  People willturn their APRS channel volume down and
> forget about it, and then they also do not hear voice calls to
> them.
> Of course you CAN monitor with CTCSS 100 from home for passing
> simplex mobiles BUT ONLY IF YOU DO NOT TX PL100 24/7.  Problem
> is that most radios cannot independently set their RX CTCSS
> without also automatically enabling their TX PL...  This is why
> we simply ask home stations to never TX with voice alert
> enabled.
> Bob
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In theory there is no difference between practice and theory.
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