A while back I made a GPS receiver module add on for the VX8-DR so that it could be used for APRS while on SOTA hikes.
The module worked well although it was not that practical for portable operation because it had to be attached somewhere (usually rubber banded to the rear of the radio) and this made the radio difficult to carry.
After a recent SOTA expedition where we were using APRS, I thought it was time to try and repackage the GPS module. One of the drawbacks of the previous module was that it had a small rechargeable LiPo battery which had to be charged.
The target is for a GPS receiver that plugs into the top connector of the VX8-DR and uses the power from the radio. The unit should also be of a similar size to the original VX8-DR module.
The old GPS module had the GPS receiver and the protocol converter board in line. The protocol converter board was moved and placed on the back of the GPS receiver. A Supertronic PP12N hobby box was cut in half to house the module and converter as this size was almost perfect.
Plugs for the VX8-DR are hard to come by at a reasonable price, so a USB programming lead was sourced from Ebay and the radio plug cannibalised. The USB plug lead doesn’t bring out the power wire, so the plug was trimmed down to the point where the pins were exposed. A U bracket was folded from Aluminium and a hole drilled in the bracket to take the plug as a tight fit. Polyurethane glue was used to fix the plug into the bracket.
It turned out reasonably well and compact as well (compared to the old one).
Some work needs to be done to make it robust such as a bracket like the original Yaesu one that provides support to the module from the antenna mount.
The photo to the left shows a button like mark on the box. This is where I was experimenting with milling from the inside and overheated the plastic. Luckily I have more of these boxes so can put another one together. A cable tie is holding the lid on for the moment.
The GPS receiver obtains a fix very quickly and works pretty well inside the house.
From this diagram,
VCC goes to Pin 2 on the accessory connector,
Ground to Pin 6,
Module RX to Pin 4 and
Module TX to Pin 5.
Things to do when time permits:
- Make a PCB for the Atmel protocol converter. Use an SMD chip.
- Make a support for the module back to the antenna mount.
- Maybe do a 3d printed box for a better package.
2018-03-10: Changed the interface PCB for an Arduino Pro Mini. This is a very compact unit that saves some space. I came across another VX8-DR GPS project from 4X1MD, and thought I would give it a try. It worked well and gets around the issue of garbage characters to the radio screen while the GPS is acquiring signal. This software uses a single serial port compared to the previous software that had a second software implemented port. There is no real need for two ports as the GPS sends to the protocol converter and the converter sends to the radio.