[aprssig] TM-D700A question
Stephen H. Smith
wa8lmf2 at aol.com
Tue Sep 6 04:20:48 CDT 2005
dave at emv.co.uk wrote:
>In any case, it only works AFIK for users with the D700 rig... D7's,
>trackers, radio's and TNC's etc, wont open a new RX audio path.
This issue generates a flame war on this SIDE of the Atlantic also every
time Bob brings it up!
From a technical standpoint, however, radios other than D700s CAN do it.
Connect the TNC directly to the discriminator of the FM rig (such as the
"9600 baud" pin of the miniDIN-6 "data" connector on a radio so
equipped) rather than the speaker jack. You can then enable PL to mute
the speaker until someone transmits a PL'ed voice signal, meanwhile the
TNC will always receive data.
Radios with TX-only trackers can do the same thing. Setting PL-muted
receive won't affect their ability to transmit. The only effect on
simple trackers like TinyTracks is that PL muting will prevent their
audio-sensing DCD channel-busy function from working to inhibit transmit
on a busy channel . You can work around this by using the "SQUELCH" or
"BUSY" line on the miniDIN-6 packet jack, which provides an indication
of activity whether or not you can hear it in the speaker. Or grab the
DC line that lights up the "BUSY" light on the front panel.
Note that the intent of "Voice Alert" is for mobiles only (never fixed
stations, especially digipeaters) to transmit the PL'ed signals. When
a PL-transmitting APRS mobile is within direct (not digipeated) range
of your PL-muted mobile (i.e. within just a few miles) your speaker will
unmute and let you hear the packet brrapps on 144.390 . Even if you
DON'T make a voice call on the APRS channel, it does alert you to the
presence of another mobile within 2 or 3 miles.
Another question: 144.800 may be safe from this in any case. Is the
Euro version of the D700, etc even capable of PL encode? I seem to
recall it only does 1750 tone bursts on keyup.
Stephen H. Smith wa8lmf (at) aol.com
EchoLink Node: 14400 [Think bottom of the 2M band]
Home Page: http://wa8lmf.com
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