The system contains a Kenwood TH-D7AG handheld, amateur band radio with builtin TNC and APRS support which is connected to a Magellan Meridian Platinum GPS. To connect the devices, I added a male DB-9 connector to the cable with a 2.5 mm plug that was included with the radio. This allows it to plug into the computer cable supplied with the GPS. This connection allows the radio to get GPS coordinates to send out as APRS packets, and also allows the radio to create waypoints on the GPS to plot the position of incoming APRS packets. One minor annoyance when the radio is connected to the Magellan (as opposed to newer Garmin units) seems to be that the waypoints created only have the last 6-digits of the incoming APRS ID. For example, the ID XX1XXX-11 would be displayed as "XXX-11". Another minor annoyance which occurs with all GPS units is that the waypoint icon is the default GPS waypoint icon, not an APRS icon. But you can manually change the waypoint icon to something else.
The radio is shown with a Comet SMA 501 antenna, which is very compact and works pretty well considering its size, but I would prefer to use something larger.
Kenwood TH-D7AG radio, Magellan Meridian Platinum GPS, and cables.
I plan on using a single waterproof bag to hold both the radio and the
GPS. Below is a picture of them both in a Voyageur waterproof bag
intended to hold a CD
or tape player. This provides protection from water, and with the
padded back, also provides some cushioning as well as flotation. The
clear flexible front allows me to see the displays reasonably well,
and also allows access to the controls for both devices. One of the
reasons I selected the Magellan Meridian GPS was for the convenient
front mounted controls.
Voyageur Waterproof bag for CD players holding Kenwood TH-D7AG
radio, Magellan Meridian Platinum GPS, and cables.
I am planning to try to modify this bag so that I can attach an
external antenna and an external earphone and microphone, while still
maintaining waterproofness. The bag already contains a 3 conducter
cable with a 3.5 mm audio jack and plug, intended for connecting
headphones to a CD player. This will work for the microphone input to
the radio. I will need to add a 2.5 mm connection for the speaker
output from the radio, and a coax antenna cable, probably with BNC
connectors for quick connection. I might also try to add a fused power
connector, to allow for an external 12 VDC power connection.
Other notes:
I downloaded the North American Marine basemap from the web, and replaced the basemap in my Meridian Platinum. Instructions for this can be found in the FAQ for the Magellan Meridian Yahoo Group. The Magellan Meridian Gold and Marine units have identical hardware (other than different colored cases). The only difference is the basemap. Apparently the marine basemap has all the same information as the land basemap, but adds additional marine information, such as aids to navigation. The Platinum adds an electronic compass, a barometer, and a temperature sensor. You can also download and install both land and marine basemaps for Europe and Australia in any of the Gold, Marine, or Platinum models.
The Kenwood TH-D7AG can be modified to allow transmitting on the Marine VHF frequencies, as well as some others. This is a farily simple modification, which requires removing two diodes. I haven't yet done this, but plan to soon. This radio isn't FCC type approved for these frequencies, so this should be an emergency-only use of this radio. I plan to get a dedicated Marine VHF for normal usage.
In any case, since I plan to have the Kenwood on pretty much all the time for APRS, I will probably use one band on the radio for APRS, and use the other to scan the appropriate Marine VHF and 2-meter ham frequencies.