[aprssig] New Yaesu mobile does APRS?
Stephen H. Smith
wa8lmf2 at aol.com
Sat Aug 17 15:56:23 CDT 2013
On 8/14/2013 1:52 PM, Kent Hufford wrote:
> In the new QST is an ad for the YAESU FTM-400DR. Says it is a touch screen
> mobile that does C4FM FDMA and shows
> an APRS screen. Even with a Father Bob asterisk.
> The opposite page is their FT1DR C4FM GPS HT.
> Will these do regular, standard 144.39mhz APRS with the stuff built-in?
> Or is this something that will be shoved over the 12.5khz data channel?
> Even has a Handmic snapshot option. Shades of the D7 and what was that camera
Note that "C4FM" (four-frequency FSK that shifts the radio's carrier between
+1600 Hz, +800 Hz, -800 Hz and -1600 Hz) is the same basic modulation scheme
used in P25 digital public safety radio. However the data transmitted on top
of this basic modulation scheme is utterly different in P25 and the Yaesu radio.
I was wondering the same thing about classic APRS interoperability. There is
no mention of classic analog TNC functionality being built-in ala TH-D7 or D72
or even VX-8.
I'm also wondering if the "mic-cam" outputs anything remotely compatible with
normal SSTV, --- or is it once again (like D-Star position reporting) only a
functional equivalent that will require a computer translation system somewhere
to inter-operate with older analog systems.
Note that the VC-H1 was completely self-contained with both cam and display
internal, requiring only RX audio in/TX audio out/PTT to connect to the radio.
I suspect the Yaesu mic-cam requires extensive support from firmware inside
the radio to function (the "SSTV" RX display is after all the radio's own
screen), meaning almost certainly the mic-cam can't be used with just any old
It would have been really cool if the mic-cam had implemented something similar
to N1VG's/Argent Data's SSTV cam board that goes from live scene to standard
SSTV TX audio inside the unit, ready to plug into ANY radio. However, Something
along the lines of the VC-H1 or the Argent SSTV board wouldn't work in the
digital modes of the Yaesu radio.
The analog-to-digital / digital-to-analog voice codecs in these digital voice
radio systems are tuned to the unique characteristics of human voices to
minimize the data rate required over the air. They just create a hideous
garbled noise on steady-state tones like SSTV, DTMF or AX.25 packet. (Have you
ever notice the "wheezing gasp" of a tone you get from the "beep" of an analog
answering machine called from a digital cell phone?) I.e. you can't just stuff
in-band audio tones from external gadgets like sound cards, TNCs, DTMF dialers,
etc into the mic input of digital radios.
You must provide a logic-level data stream directly to the digital side of the
radio, in whatever logic level/error coding/block size/header-formt/etc
the radio's data transport format requires.
By the way, I finally got a TH-D72 after a successful day at a local swapmeet
where I retired my TH-D7AG. Last night, I verified that the D72 does indeed
work perfectly with the VC-H1 handheld SSTV device. Further, the VH-H1
combined with the built-in GPS in the TH-D72 makes for the ultimate
self-contained setup for my mobile APRN (Automatic Picture Reporting System)
that combines SSTV and APRS.
With the D72 set to beacon on unkey of PTT (rather than automatically at
intervals), it is trivially easy to tag each SSTV transmission with an APRS
posit at the end of the picture transmission. [I did do this with the TH-D7
but had the added complexity and messiness of an external GPS to deal with.]
Stephen H. Smith wa8lmf (at) aol.com
EchoLink: 14400 [Think bottom of the 2-meter band]
Home Page: http://wa8lmf.net
Long-Range APRS on 30 Meters HF
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