Communications in my RRC will include 2m Amateur Radio, Automatic Packet Reporting System (APRS), and the US Coast Guard weatherband. The NW Overland Society uses 2m for vehicle to vehicle trail communications. APRS allows me to see other APRS equipped vehicles on my GPS in real-time. US Coast Guard’s Weather band makes it easy to keep appraised of changing weather conditions. The goal is to get all of this into the truck in a way that performs well, is reliable, and looks like it could have come from the factory.
Creating a setup that meets these goals and is easy/convenient to operate is a challenge. Many Overland vehicles are covered in antennas, computers, amateur radios, SPOT messengers, handheld GPS units, dash mounted phones, iPods, and CBs. It gets a bit ridiculous after a while. I long ago decided that my phone, SPOT, iPod, and other devices that don’t require my interaction while on the trail get put away in my seat bag. I’m fortunate to not have to use a CB with our group, leaving only the HAM radio and Navigation devices to contend with in the cabin.
The setup I decided to go with is much harder to setup than a Kenwood D710a. If you are looking for an easy to install, turnkey solution for Amateur Radio communications AND APRS then just get the Kenwood. I’m going to a lot of trouble to get a slightly cleaner installation and a couple of additional features.
I’ve elected to go with the Icom 2720h 2M/440MHz Dual Band mobile radio that I kept from my Discovery II. This radio is small, displays green to match my dash, integrates beautifully with 3rd party APRS trackers/TNCs, has weather band support, has been a reliable performer for me in the past. Besides, I own it so it’s FREE and this is a budget build afterall. The radio is essentially 2 radios in one housing that share an antenna. It can be configured so that the APRS communications happen on the sub-band (secondary radio). If it is transmitting on the sub-band and I press the microphone to talk on the main band it will stop transmitting on the sub-band. It automatically mutes the microphone when transmitting on the sub-band. These sound like standard *expected* features, but in my experience the Kenwood D7xx and the Icom 2*20h series radios are the only ones that support this. This radio doesn’t have APRS built in, so I’ll pair it with a 3rd party TNC/Tracker.
For the TNC/Tracker I’ve selected a Byonics TinyTracker4 (TT4). Using a separate tracker, increases the amount and complexity of the wiring required to get an APRS setup working. The benefit to me is that I can use a radio with a smaller faceplate and thanks to the author for adding a couple of custom features it will also allow me to beacon my position when Overland Navigator isn’t up and running.
The Kenwood D710a and other trackers integrate with Overland Navigator (Computer) with two separate wires like this:
While the TT4 can integrate that way, it has a couple of extra features built in that allow it to integrate without requiring the computer to be up and running (or even installed). This configuration makes sense because most people leave their radio permanently installed in their vehicle, whereas the computer tends to be frequently installed/uninstalled.
In this configuration the GPS sends it’s signal to the TT4. The TT4 uses this GPS information to decide when to send out an APRS position report over the radio. If Overland Navigator is running, the TT4 relays this incoming GPS information to it. Overland Navigator uses this GPS input to determine where it is currently located. Only one connection goes into the computer running Overland Navigator; a second GPS isn’t required because the TT4 provides the GPS input required. When the radio receives someone else’s APRS position report over the air, it delivers it to the TT4, which decodes the APRS packet and forwards it to Overland Navigator as an NMEA (GPS) waypoint in a format that includes the appropriate APRS symbol.
I selected a US GlobalSat MR-350P permanent bulkhead mount GPS. It is a WAAS/ EGNOS enabled external GPS receiver which when activated can provided sub 3m accuracy. It utilizes a bulkhead (7/8" through-hole) style mounting design for a more permanent weatherproof and factory looking installation. The receiver has an active patch antenna and uses the “20” channel SiRF Star III high performance GPS chipset that is very sensitive, even under tree cover. IPX7 Water Proof Design (Immersion for 30 minutes at a depth of 1 meter).
I decided to get everything working on the bench before running out to the truck and installing things. This turned out to be a good choice. I wound up having to make a custom cable and testing with my desktop computer made the entire process easier. I use a 12V 10 amp power supply from Radio Shack to simulate the 12VDC battery in the truck.
The radio wiring is straight-forward. I simply connected the handset, faceplate and antenna to the radio. Ran the positive and negative wires directly to the battery (power supply). and turned it on.
Once you I had power to the Icom 2720h, I had to configure a number of things to run APRS & voice at the same time. With these instructions it takes about 5 minutes.
- Select the Left Side as the main band by pressing the left side’s “Main” button.
- Configure “Initial Set Mode” settings
- Enter Initial Set Mode
- Power off the radio
- Power on the radio while simultaneously pushing the [SET] button (P 60 of the manual)
- Setup the Right Side of the panel for packet mode (p 62 of the manual)
- Press the [SET] button repeatedly until you see “paC” on the LCD
- Rotate the left band’s [DIAL] to select “paC – r” on the LCD
- Set the packet speed for 9600 baud
- Press the [SET] button until you see “bpS” on the LCD
- Rotate the left band [DIAL] to select “bpS – 96”
Note 1: This will mute the microphone during packet transmissions, so you won’t have to unplug it.
Note 2: During voice operations, data transmissions will be suprressed. Vx has priority.
Note 3: Flashing ‘S1’ will appear in the lower right corner when transmitting on voice.
Note 4: You can still run 1200 baud packet, the 9600 baud setting enables “Dual Mode”.
- Exit “Initial Set Mode”
- Set Sub-band frequency
- Rotate the right band’s [DIAL] to tune the frequency to 144.390MHz.
This is the common APRS frequency and positions sent to this frequency will be gated to the internet. http://aprs.fi
The NW Overland Society uses 147.460 when on the trail. We use 147.50 if the other frequency is busy.
The Tiny Tracker 4 (TT4) is a hub as it connects to 12VDC power, the radio, and the GPS.
The tracker can receive power directly from the battery as it accepts a wide range of voltages making it safe even when starting. I’m going to use a relay, but haven’t decided if I’ll switch it off the ignition switch or a separate toggle.
The tracker plugs into this radio using the Byonics M12P cable. One end plugs into the radio/power side of the TT4, and the other end goes to the 6 pin mini DIN “Data” port on the Icom 2720h base unit.
In order to interface to both a GPS and a PC at the same time, I used Byonics “TinyTrak4 Serial Splitter and Null Modem Adapter”. This cable is described on the Byonics website as:
This adapter will split the 2 serial ports available on TinyTrak4 J2 to two separate DB-9 connectors. The computer side in the primary port, contains a null modem adapter and will plug directly to a computer serial port. The GPS side is the secondary port, will plug directly to a GPS serial DB-9 plug, and carries the GPS power on pin 4. This cable can also be used to update the TinyTrak4 firmware, and connect with the Configuration software. With it, the above null modem adapter/cable is not needed. Note: Only the TinyTrak4 Alpha firmware supports the second serial port at this time. Other firmware does not.
The “GPS” side is used to connect to the GlobalSat MR-350 GPS. I’ll document that in the GPS section.
I plugged the “Computer side” into my computer using a Serial to USB converter. This connection is used to configure the TT4 and later is used to provide GPS input to Overland Navigator.
Once connected to the computer I updated the TT4 to the latest firmware and configured the device for use with Overland Navigator. Many of the options required to use the TT4 with Overland Navigator are not available via their Windows configuration utility. The TT4 supports a “terminal mode” that allowed me to access all settings.
This required me to obtain a Vista 64 based terminal emulation program. I found the Indigo Terminal Emulation Program from a company called ShadeBlue Software. http://www.shadeblue.com/products/indigo/default.aspx I configured it for the COM port where I had connected the TT4, set it to 19200bps, N, 8, 1 and hit connect. I hit ESC 3 times when prompted and I was in.
I set the following TT4 settings by simply typing the following one at a time:
BMODE GPS – to setup the TT4 port the GPS is connected on
BBAUD 4800 – to set the GPS baud rate
PPERIOD 300 – to set the position report rate to 5 minutes
DIGI1 WIDE1-1 – to set the first digipeater in your requested path
DIGI2 WIDE2-1 – to set the second digipeater in your requested path
WYPTXT TRUE – Send waypoint info to the PC cable
PKTICOM FALSE – Don’t send the raw APRS data stream to the PC cable
GWAYLEN 20 - Long waypoint names
GWAYMODE KENWOOD – Send Overland Navigator the Kenwood Waypoint format that includes APRS symbols
GRELAYBITS 3 – Relay all the GPS data on the GPS cable out to the PC cable (Input to Overland Navigator)
GRELAYRATE 1 – Relay all GPS data. Don’t skip any.
TSWPT FALSE – Don’t send a waypoint for ourself
ABAUD 4800 – Set PC cable to 4800 baud
SBEN TRUE – to enable Smart Beaconing
At this point I exited the terminal session in Indigo, changed the baud rate to 4800, then reconnected. I saw gibberish as expected since the TT4 is outputting 19200. I power cycled the TT4 and started seeing APRS stations that were heard. GPS data wasn’t available yet, because the GPS hasn’t been wired up.
NOTE: Byonics offers a plug and play GPS with the same chipset as the GPS I’m using. Their GPS works out of the box with the TT4. I selected the GPS I did because it mounts on the outside of the vehicle and looks like a factory installed option.
I plugged the “GPS” side into my GPS using a custom built cable. The custom cable allowed me to power my GPS using the same connection I was transferring the GPS data on. This isn’t normal as most Serial GPS units get power from a battery or a cigarette lighter. My GPS ran off 5v instead of 12VDC so I needed a power source. I was very happy to learn that the TT4 provided 5VDC on this connection. In the end I have very simple wiring for what is traditionally a fairly complicated thing to get working in a vehicle. In order to get the 5VDC on pin 4 of the GPS connector I followed the “Getting Started Guide” and configured the JP6 jumper on the TT4.
The GlobalSat MR-360 has a male PS2 port that normally connects to either a USB pigtail or a serial pigtail. The serial pigtail has both a DB9 connector and a PS2 connector and requires power be provided on the PS2 connector. After digging around the internet for wiring schematics for the GPS I decided to create my own pigtail that was DB9 serial and that also provided power to the GPS on PIN 2.
So the GPS has a male PS2 connector and the TT4 has a male DB9 serial connector. My custom cable has a female PS2 port on one end and a female DB9 connector on the other with the following wiring:
PS2 PIN 4 –-----> DB9 PIN 2 (+5v)
PS2 PIN 2 ------> DB9 PIN 5 (GPS Tx)
PS2 PIN 5 ------> DB9 PIN 1 (GND)
With the last cable wired up, it was time to give it a test. I plugged the GPS cable in, and the TT4 green GPS LED lit up. Good sign!
Time to test with the terminal emulation program to see if the TT4 is outputting it’s GPS input to the PC cable as NMEA0183. Success!
Last but not least, is a check to see if it works with Overland Navigator. Yep, we have GPS position info (red dot). We even have another APRS station showing up on the screen within the first 2 minutes of testing.
A quick check on aprs.fi shows that the TT4 is sending that position out to the world over the radio.
Setting up a TT4 is significantly more complicated than it was to setup the Kenwood D710a. And unlike the D710a, I can’t tweak the settings easily in the field. Hands down, the Kenwood is easier to setup and use. I’ll continue recommending it to Overland Navigator customers.
The TT4 offers additional configuration and functionality that just isn’t available with the Kenwood. With a couple of evenings worth of work I was able to get all of the wiring sorted out in a way that will allow for a simple installation in the vehicle. Though more difficult to setup, the TT4 and Icom 2720h can be tucked away, which will yield a very clean install into the vehicle. Finally, the TT4 will make it easy to add APRS messaging to Overland Navigator.
Now that everything is working solidly on the bench, the next step will be to get it installed and working in the vehicle. Stay tuned…