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Kenwood TH-F7E Interface

Kenwood TH-7FE PC Interface Construction

Introduction

Although it was perfectly possible to program the radio via the buttons it was soon clear that doing it from my PC would be much easier! I knew that Kenwood supplied a PC interface, but a little Googling found Build your own Programming Cable which gave detailed examples of various implementations of the interface all following the same basic circuit diagram. I decided to build the best documented one (To long in IT!) and besides I doubted I had the skills to scratch build the SMT version..

Construction

“If you can't solve the problem, change it..”

Components were sourced from my Brothers parts collection (!) and Maplins, assembled, then very carefully checked and checked. Even on such a small circuit the scope for misplacing (for me at least) components or wire links is immense. But this proved not to be the problem..

Testing

Construction proceded quite rapidly, then time to test. I downloaded the Windows software from Kenwood Inc Amateur Radio Home Page then connected the radio up. "Timeout" Oh dear things were not working. Next I checked the COM port and generally looked things over. The interface certainly seemed to be wired correctly and the software "should" work. Over the course of several days on and off I checked voltages and rechecked the circuit. I was stuck as I only had the vaguest idea of how the circuit was supposed to work and I could not be certain the software was working..

Bread boarding

Kenood TH-F7E Bread Board Version
Bread Board Version

Seeking a way forward, I built the circuit again on bread board, checking again as I assembled, an interesting exercise but exactly the same result.

Opportunities

Well, as they say if you can't solve the problem change it.. So I found the command set connected everything back up again and used hyper terminal to see what I could send or receive from the radio. I could send commands to the radio but got no response from it. Progress. I then read that people had problems with the 2.5 mm speaker socket on the radio, having to file the face of the plug so it fitted better. This solved the problem!!

Kenwood TH-F7E Circuit Board Closeup
Circuit Closeup

Completion

A suitable box was found. The interface is proving very useful, much easier to program the radio. The PC file format used to store the radio settings is also easy to edit if you have a lot of data to enter. Kenwood only supply a Windows version of the program and have no plans for a Linux version, so an Open Source Linux version may be a future project!