Older Kenwood mobiles, like the TM-D700 I own, have a GPS input to connect an external GPS device in order to send APRS packets with your position data to the network. You can find a ready made GPS mouse, but the cost is around 70-80 USD.
You can build your own GPS mouse for around 15-20 USD if you buy the necessary components from eBay or other Chinese suppliers. If you choose eBay then search for the following :
1. NEO-6M GPS MODULE (about $10,00)
2. MAX3232 CONVERTER (about $2,00)
3. 5V USB STEP DOWN MODULE (about $2,00)
You will also need a small plastic box (about $4,00). That's all you need.
Check the photo below for the components (the USB step down module in not shown because it's housed in another box in my car, serving also other devices).
The above modules need 3.3 to 5 Volts to operate properly. This is why you need the USB step down module. When ordering the USB step down module pay attention to order one that accepts 24 Volts input. If you order one that accepts only 12 Volts, then you will most likely burn ALL the connected modules because the car alternator supplies much higher voltage (mine supplies at peaks almost 16 Volts) and WILL burn the step down module.
Only 2 wires needed between the GPS and the MAX3232 module. Just connect the GPS output (TX) to the TTL input of the MAX3232 (RX) and of course the common ground. You don't need other connections.
The RS232 to TTL converter is needed because the TM-D700 accepts RS232 signals and the NEO-6M GPS module provides TTL signals. Don't forget to connect the 5V supply from the USB step down module and of course the common ground. Check the connections below :
The RS232 output (TX) from the MAX3232 module goes directly to TM-D700 gps input. If you have the original gps cable that came with your transceiver, then you must connect this to the white cable (some others report the red cable, I guess different batches may have different colors). Of course, don't forget to connect the common ground. If you don't have the original cable, then you can make your own like the schematic below :
Here are the main components inside the plastic box. It's size is slightly larger than a matcbox. Later, using a hot glue gun, you can secure the cables and the modules inside the plastic box to avoid the mechanical stress from car vibrations.
And finally a few words about the USB step down module. I got this one :
I use it for about 2 years without a problem. I kept the usb connector and I put it in a small plastic box near the instrument panel of my car. I soldered 2 cables that go to the NEO-6M and MAX3232 modules for the power supply and I added a small switch at the input in case I need or want to disable the gps by cutting the power.
Please have in mind that NEO-6M GPS module works at 9600 bps, so in order to work with your TM-D700, just go to the relative menu setting and change the gps speed from 4800 to 9600 !
That's all... The whole system is working flawlessly for more than 2 years at extremely high temparatures inside the car. Now you can transmit your position data to the APRS network.
73, Fanis
SV1BGM
You can build your own GPS mouse for around 15-20 USD if you buy the necessary components from eBay or other Chinese suppliers. If you choose eBay then search for the following :
1. NEO-6M GPS MODULE (about $10,00)
2. MAX3232 CONVERTER (about $2,00)
3. 5V USB STEP DOWN MODULE (about $2,00)
You will also need a small plastic box (about $4,00). That's all you need.
Check the photo below for the components (the USB step down module in not shown because it's housed in another box in my car, serving also other devices).
 |
| NEO-6M GPS Module and MAX3232 RS232 to TTL |
Only 2 wires needed between the GPS and the MAX3232 module. Just connect the GPS output (TX) to the TTL input of the MAX3232 (RX) and of course the common ground. You don't need other connections.
The RS232 to TTL converter is needed because the TM-D700 accepts RS232 signals and the NEO-6M GPS module provides TTL signals. Don't forget to connect the 5V supply from the USB step down module and of course the common ground. Check the connections below :
The RS232 output (TX) from the MAX3232 module goes directly to TM-D700 gps input. If you have the original gps cable that came with your transceiver, then you must connect this to the white cable (some others report the red cable, I guess different batches may have different colors). Of course, don't forget to connect the common ground. If you don't have the original cable, then you can make your own like the schematic below :
Here are the main components inside the plastic box. It's size is slightly larger than a matcbox. Later, using a hot glue gun, you can secure the cables and the modules inside the plastic box to avoid the mechanical stress from car vibrations.
And finally a few words about the USB step down module. I got this one :
I use it for about 2 years without a problem. I kept the usb connector and I put it in a small plastic box near the instrument panel of my car. I soldered 2 cables that go to the NEO-6M and MAX3232 modules for the power supply and I added a small switch at the input in case I need or want to disable the gps by cutting the power.Please have in mind that NEO-6M GPS module works at 9600 bps, so in order to work with your TM-D700, just go to the relative menu setting and change the gps speed from 4800 to 9600 !
That's all... The whole system is working flawlessly for more than 2 years at extremely high temparatures inside the car. Now you can transmit your position data to the APRS network.
73, Fanis
SV1BGM
