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I recently purchased a T3-Mini to enable APRS plotting and beaconing with my Yaesu VX-7 and my Garmin GPSMAP 496 via a CT-H4 cable.
Please see attachment for the schematic.
In configured the T3-mini for NMEA mode (4800 baud). All other settings remained in default.
The Garmin 496 offers a variety of serial data formats:
Garmin Data Transfer - —the proprietary format used to exchange data with a PC or another Garmin GPSMAP 496. Garmin Data Transfer is disabled when the USB is connected and the unit automatically switches to USB format. When the USB is
disconnected, the USB field changes to Transfer Mode.
Garmin DGPS — used to connect the GPSMAP 496 with a Garmin DGPS beacon receiver.
Garmin remote Sonar —supports the input/output of a Garmin remote sonar device.
NMEA in/NMEA out — supports the input/output of standard NMEA 0183 version 3.01 data and sonar NMEA input support for the DPT, MTW, and VHW sentences.
Aviation in — the proprietary format used for connection to a Garmin panel-mounted GPS receiver. Allows the GPSMAP 496 to show a Go To or route selected on the panel-mounted GPS receiver. This eliminates the need to enter the destination on both units.
Aviation in/NMEA & VHF out — receives aviation data and transmits out both NMEA data, at 9600 baud, and VHF frequency tuning information to a Garmin Nav/Comm radio.
TIS in — receives TIS data from a Garmin Mode S transponder.
TIS in/NMEA & VHF out — receives TIS data and transmits out both NMEA data, at 9600 baud, and VHF frequency tuning information to a Garmin Nav/Comm radio.
RTCM in — allows Differential GPS (DGPS) input using a standard RTCM format.
RTCM in/NMEa out - allows Differential GPS (DGPS) input using a standard RTCM format and also provides NMEA 0183 version 3.01 output.
RTCM in/text out - —allows Differential GPS (DGPS) input using a standard RTCM format and also outputs simple text data that includes, data, time, location, and velocity.
Text out - allows the unit to output simple text data that
includes, data, time, location, and velocity. The Baud can be set
to 1200, 2400, 4800, or 9600.
None — provides no interfacing capabilities
I selected NMEA In/ NMEA Out. The Advanced NMEA Output Setup Page allows to set the output rate, change the precision of the Lat/Lon minutes, set Waypoint IDs to names or numbers, as well as turn on and off the GPS status, the GARMIN Proprietary sentences, and Waypoint/Route (WPL, RTE).
GPSMAP 496 NMEA
Sentence Output (NMEA version 3.01 compliant):
Always transmitted: GPRMC, GPGGA, GPGLL, GPBWC, GPVTG, GPXTE, GPRMB
Switchable sentences: GPGSA, GPGSV, GPWPL, GPRTE
GARMIN proprietary: PGRME, PGRMZ, PGRMM, PGRMH
I selected normal output rate. Fast does not work, even when putting the T3-Mini into 9600 baud.
Using the above described setup the T3-Mini begins blinking the green LED, after a while this is accompanied by red flashed, whenever the Yaesu VX7 receives and APRS packet. The T3-Mini also briefly activates PTT every once in a while, but no actual beacon is sent out. I can activate PTT from the firmware software and also send and hear the two different tones.
However, the plotting and beaconing features do not work at all.
WHAT I HAVE DONE SO FAR
All other Garmin 496 serial formats including "Garmin Dat Transfer" formats. They did not work, i.e. the T3 does to even detect the GPS position, does not detect an APRS packet or attempts to send a beacon. No variation of any of the advanced NMEA settings enabled plotting beaconing.
I also tested a setup with my Lowrance GM 100. The problem is exactly the same. GPS detection in NMEA mode yes, plotting and beaconing no.
Lowrance Globalmap GM100: http://gpsinformation.net/main/gm100rev.htm
It is inconceivable to me that two independent, advanced GPS mapping receivers do not perform the advertised function of the T3-Mini i.e. APRS plotting and beaconing. The Garmin 496 is capable of plotting data from various sources, i.e. sonar, TIS etc. Why would APRS plotting not work? I assume I made a mistake.
What am I doing wrong?
Garmin 496 manual: http://avsport.org/acft/Garmin/gpsmap496_ownersmanual.pdf
Garmin 496 pc wiring instructions: http://www8.garmin.com/specs/pcwiring.pdf
GPSMAP® 496 | Garmin
Garmin 496 power/data cable (bare wires): Power/data Cable (bare wires) | Garmin
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