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[aprssig] Mic-E and non ham aprs use

Andre aprs at pe1rdw.demon.nl
Thu Jun 7 18:19:49 UTC 2012

On Thu, 07 Jun 2012 19:51:09 +0200, Stephen H. Smith <wa8lmf2 at aol.com>

> On 6/7/2012 1:08 PM, Andre wrote:
>> 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.
>> 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.
>> 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?
> 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".
The kenwoods will be left out because the red cross already has it's own
trancievers so guess it will have to be a TinyTrack 3 or better or a

> 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.
Yes it's why I asked about 9k6

> 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??).
144.800 is out of the question, it will have to be trough the output or a
rarely used uhf frequentie as nearly everyone involved will not be a ham
and will definatly not be using ham callsigns.
> 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.
> (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.)
> 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.
The transievers in use are icom landmobile analog radios that have all
lines available at the back so connections should not be a problem
> -------------------------------------------------------------------------------
> 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.
> 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.
> 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.
The radios don't have the ham datajacks but do offer access to both voice
input and "data" input on seperate pins so that should not pose any
problem as wel
> -------------------------------------------------------------------------------
> --
> Stephen H. Smith    wa8lmf (at) aol.com
> Skype:        WA8LMF
> Home Page:          http://wa8lmf.net
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73 Andre PE1RDW

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