The Icom IC-9700 has a GPS data input available but no oficial accessory from Icom. It’s a 2.5mm TRS connection that allows users to connect a GPS unit with an RS232 output to the IC-9700 and use that data for DSTAR transmission. There are several GPS units on the market that can provide the data but they are often expensive standalone units or cheaper, older generation units with lower sensitivity and performance when it comes to tracking GPS satellites.
I wanted a cheap, compact solution with good performance and an external antenna so I built my own.
GPS Puck unit with RS232 output – https://www.aliexpress.com/item/32878492421.html
12v to 5v Regulator – https://www.unmannedtechshop.co.uk/product/micro-bec-voltage-regulator-3-3v-5v-12v (My GPS needed 5v.)
Screw Terminal DB9 connector – https://www.aliexpress.com/item/32879710103.html (Make sure it’s the correct fitting to match your chosen GPS connector. Mine was the Male Nut version.)
2.5mm TRS audio lead – https://www.ebay.co.uk/itm/2-5mm-GOLD-Stereo-Jack-to-2-5-mm-Jack-Audio-Cable-Lead-5m/192884532103
Construction is very simple. The regulator fit’s inside the screw terminal DB9 shell providing 5v to the GPS unit using the 13.8v supply from the radio PSU. The RS232 serial data is then passed to the IC-9700 via the 2.5mm TRS audio lead.
The finished adaptor complete with external GPS unit.
As expected, it works very well and allows users to place the GPS antenna outside where it has a good view of the sky. For a total cost of less than £20 including the postage, I am very happy with it.
— UPDATE —
I’ve had a few questions about how my adaptor is connected. Below are the basic details. Remember this could be different for your GPS.
2.5mm Jack Tip – DB9 Pin 2 (TX Data on my GPS unit)
2.5mm Jack Ring – DB9 Pin 3 (RX Data on my GPS unit)
2.5mm Jack Sleeve – DB9 Pin 5 (Ground on my GPS Unit)
+5v from regulator – DB9 Pin 9 (DC 3.6V-5.5V supply on my GPS unit)
-v from regulator – DB9 Pin 5 (Ground on my GPS Unit)