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[aprssig] PIC processor for APRS info for D-STAR mobiles?

John Habbinga kc5zrq at gmail.com
Tue Jul 8 13:04:25 UTC 2008


>> Yep, except it does "break squelch" in that there would be at least one
>> beep for every transmission through a repeater.

There is not a beep on a D-STAR repeater.  If you hear a beep, then
that is a function of your radio and it can be turned off, in which
case the end user will hear nothing when a data transmission takes
place.

If the signal is very
>> weak, there could be audio generated on the receiver if the forward
>> error correction gets defeated (this happens, the generated audio is
>> "affectionately" called the R2D2 effect).

This can happen, but is very infrequent when sending short data only bursts.

> Forgot one more thing: if a transmission with silence for audio ("data-only") is being received correctly (no R2D2), the other people trying to use the frequency for voice communications will likely key up over the data causing both transmissions to be lost (similar to a collision in AX.25 or doubling on a repeater).  The only way to avoid this is for all the voice communicators to always be looking at the radio (which shouldn't be happening when driving ;-).  While most of the radios will not transmit on an in-use channel based on "auto-transmit when data available on the data port", they will transmit when you physically press the PTT button.

This is a fact, but it can be avoided by turning on "Repeater Lockout"
(RLO) on the users radio.  This brings up an interesting thought.
Data being transmitted through the serial port connection will hold
off until the air is clear.  Location data from a GPS being "beaconed"
in GPS mode does NOT hold off and will interrupt in progress voice
communications.  This is a good argument for using an external
DPRS/APRS type encoder instead of beaconing in GPS mode.

I would also encourage two-way APRS/DPRS activity to take place on a
simplex frequency, not a repeater.  145.670 MHz can be used for DPRS
and simplex voice calling with very little problems.  DPRS activity
over the repeater can be limited to sending position information with
PTT or limited rate beaconing.




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