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On 6/7/2012 1:08 PM, Andre wrote:
<blockquote cite="mid:op.wfjlv41kmwiqe0@huiskamer.fritz.box"
type="cite">besides being ham I'm also communication volunteer for
the dutch red cross and my region is looking into assets tracking,
currently google earth is used but this is manual so I figured
APRS could play a good roll in that especialy as it is
bidirectional.
<br>
The need is not a constant update of every station as posts only
rarely move so only a position burst after a transmition is more
then enough like it was done with the original Mic-E trough
repeaters, also the frequenties and radios are limited so it is
likely that data bursts will have to go trough the voice channel.
<br>
So the question is what trackers there are that still have the
original Mic-E function of appending the data burst after the
transmition and wich ones are capable of 9k6?
<br>
</blockquote>
<br>
The TinyTrack III and Tigertronics TigerTrack TM-1 can both do this
burst on unkey, as can the Kenwood D700, TH-D7, D710 and TH-D72
APRS radios with built-in TNCs. You enter the Kenwood APRS menu and
by change their beacon mode from "AUTO" to "PTT". <br>
<br>
The standalone trackers can only do 1200 baud. The Kenwood radios
with their built-in TNCs can also effortlessly do 9600 as well.
The 9600-baud bursts-on-unkey are almost un-noticeable to the users
-- the 9600-baud data stream sounds almost like white noise and
blends into the receiver squelch crash that follows it.<br>
<br>
The 1200-baud bursts are quite noticeable to the user. The
traditional approach, if doing voice operation through a repeater is
to attach a TNC, configured as a digipeater, to the repeater receive
audio. When it hears packet CARRIER DETECT, it mutes the repeater
retransmit audio briefly. The transmit side of the TNC keys up a
separate transmitter at the repeater site that transmits on the
usual APRS frequency (144.800 in your case??). <br>
<br>
<br>
<br>
The external trackers have to be able to monitor the state of the
radio's microphone PTT line to trigger the burst-on-unkey. In the
case of the TinyTrack, the device must be in SERIES with the mic PTT
line; i.e. the TT has separate MIC PTT-in (that monitors the state
of the MIC button) and TX PTT-out (that actually keys the radio)
pins. <br>
<br>
(For this type of Mic-E operation, I have a TinyTrack packaged in a
small metal box with a female mic jack on one end, a male mic plug
on a 15 cm cable (to go to the radio) coming out the other end, and
a DB-9 male connector (to mate with a serial GPS) coming out the
side. The unit is powered by the 8 VDC present on one of the
conductors from the radio mic jack. I was able to power a
very-low-power GPS plugged into the box from the same 8 VDC source.
You unplug the existing mic from the radio, plug it into the jack on
the box, and then plug the box into the radio's mic jack.) <br>
<br>
<br>
The TigerTrack has a single tri-state I/O pin that bridges the mic
PTT line in parallel. Normally it presents a high-Z CMOS-type input
as it monitors the state of the PTT line. When it sees the PTT line
go low (mic PTT button pushed) and then return to the high state
(mic button released), the single pin changes function and becomes
an active-LO output that shorts the PTT line to ground to key after
the voice transmission. I.e it's edge-triggered when it sees a
LO-to-HI transition on the mic PTT line. <br>
<br>
<hr size="2" width="100%"><br>
<br>
1200 is easy to interface - basically just parallel the microphone
and tracker TX audio at the radio mic jack. For 9600, you need
direct DC-coupled access to the transmitter's FM modulator.<br>
<br>
This means cutting into the radio somehow, unless the radio has the
6-pin mini-DIN "data" or "packet" jack --AND-- configuration or menu
support for 9600 baud mode. The DIN connector has two receive
outputs: One is normal de-emphasized RX audio for 1200-baud
operation. The other is a direct DC-coupled connection to the
receiver discriminator that supports 9600-baud receive. <br>
<br>
However on TRANSMIT, the DIN jack has only ONE connection. The
radio must provide an explicit jumper or configuration menu option
for switching this single pin's function from audio input for the
1200 & 2200 Hz audio tones used for 1200 baud to the direct TTL
logic-level data stream used for 9600-baud operation. <br>
<br>
<br>
<hr size="2" width="100%"><br>
--<br>
<br>
Stephen H. Smith wa8lmf (at) aol.com <br>
Skype: WA8LMF<br>
Home Page: <a class="moz-txt-link-freetext" href="http://wa8lmf.net">http://wa8lmf.net</a><br>
<br>
<br>
High-Performance Software-Only Packet TNC <br>
<a class="moz-txt-link-freetext" href="http://wa8lmf.net/miscinfo/UZ7HO-Soundmodem-Install-Ver-0.44-Beta.exe">http://wa8lmf.net/miscinfo/UZ7HO-Soundmodem-Install-Ver-0.44-Beta.exe</a><br>
<br>
High Quality Calibrated Static Maps for Any APRS App <br>
<a class="moz-txt-link-freetext" href="http://wa8lmf.net/aprs/PM9_StaticMap_Export.htm">http://wa8lmf.net/aprs/PM9_StaticMap_Export.htm</a><br>
<br>
Vista & Win7 Install Issues for UI-View and Precision Mapping<br>
<a class="moz-txt-link-freetext" href="http://wa8lmf.net/aprs/UIview_Notes.htm#VistaWin7">http://wa8lmf.net/aprs/UIview_Notes.htm#VistaWin7</a><br>
<br>
<br>
"APRS 101" Explanation of APRS Path Selection & Digipeating <br>
<a class="moz-txt-link-freetext" href="http://wa8lmf.net/DigiPaths">http://wa8lmf.net/DigiPaths</a> <br>
<br>
<br>
<br>
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