[ao16aprs] Re: [ss] Re: info

["Tim Cunningham" <tim_cunningham@mindspring.com>]

>As to radios, any radio will work.  The TM-V7A is very flexible.  It will
>allow you to run APRS on VHF and allow you to talk on VHF at the same time.
>I have one and I really like it.  Order the kit to mount the display in
>another place.  I can never find a good place in today's cars/trucks to
>mount the radio where it is a good viewing spot.
>
>Scott



Does the TM-V7A have a PTT line on the microphone or is the PTT signal
digitally encoded from the microphone like many of the other new radio's
on the market?

I have another brand of radio I have been using with an APRS Mic-Encoder,
but there is no PTT line on the microphone plug.  Instead, the PTT signal is
encoded on a serial stream of data to the radio from the microphone and
the radio decodes the information.  The APRS Mic-E does not work with
this type of arrangement at all, unless you get real creative with some
fancy
modifications to the radio.  The radio I am using has a 1200/9600 packet
connector on the back of the radio that I wired to the Mic-E, but I had to
modify the radio to the get a decoded PTT signal back to the Mic-E so it
would hold the PTT line at the packet jack on the  radio.  Unfortunately,
when the PTT is dropped from the microphone, the radio unkeys before the
microprocessor in the radio looks at the PTT signal at the packet jack.
This
is a real pain.  The result is that my signal drops momentarily when I unkey
the microphone and rekeys the transmitter when it discovers that the PTT
is activated from the packet jack (PTT challenged).  So, when I am on a
voice repeater and unkey the microphone using my Mic-E, there is a short
squelch tail before the data from the Mic-E is presented at the end of a
transmission.  This requires the end of transmission to be longer in order
for the transmitter to settle and send the APRS posit which equates to
about 200-300ms longer than what it really should be if the transmitter did
not
drop in the first place.  Considering that most courtesy beacons are more
annoying than the Mic-E posit, it may not matter anyway.

Anybody who wants to use a Mic-E or similar device on some of these new
radio's should be aware of this condition as a Mic-E will not work without
some radio modification if the radio does not have a dedicated PTT line.
In some cases it may not be possible or require major effort.

If one wants to merely use a radio for APRS on 2M just to beacon on the
APRS network, most radio's that have a packet data jack or a true hardwired
old fashion PTT line on the microphone jack can be utilized.  Most can be
modified if they do not meet the above requirements.  However, my point
is specifically directed to those who may be interested in using a Mic-E or
similar device to attached an APRS packet posit at the end of a voice
transmission.



73's,

Tim - N8DEU
Huntsville




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