Since the FTM-100 is always drawing power even when switched “off” and for safety, I have added an in-line power switch. This actually comes via a relay from the right handlebar switch  remembering that the power the rig draws can be significant (High power Tx on 70cm ~13amps+)

The connections to the PTT, Mic and speakers all run via the Microphone and speaker sockets on the main body of the FTM-100. (You could use the DATA port if you prefer.) To keep things simple, I took a spare microphone for the FTM-100 (the MH 48) and removed the Mic capsule and PTT switch from the circuit board, leaving the rest of the unit in the case. The reason for this is that the FTM-100 uses a powered non-standard electret mic element (needs to be exactly 1.2KΩ)

The wires run away as follows:-

  • PTT+ and PTT- to a non-latching switch on the left handlebar and in parallel to a locking switch on right handlebar switch pod.

  • Mic+ and ground via the interface box (the old mic unit) and

  • Speaker+ and ground via the speaker socket to the helmet.

  • A second speaker line has been run to a waterproof loudspeaker on the bikes dash from the speaker socket, but I have added a switch so I can silence it if required.

The speaker and microphone built into my helmet has a safety break away connector, to allow disconnection getting off the bike, but more importantly to come away if I unexpectedly part company with the bike whilst riding it! This is done with a waterproof 6pin DIN plug and socket (plug = helmet end) although it is possible to use a ¼” stereo jack and line socket, which I previously used for many years on my old Honda Silverwing. The important thing is the socket should be waterproof to prevent corrosion.


Mounting the antenna…

 Antenna on TB1  ant bar  ant bar2

It’s worth mentioning the antenna setup for a second, after all this is really the business end of the radio.  A poor antenna mounting is worse than useless and could damage the rig.

 Link to ST13 wiki drawings for an antenna bracket.

Whatever type of antenna you use, it must be strong, and mounted to a good earth. When fitted on a car, there is a massive ground plane under the antenna. You don’t have this on a bike so I found the best way was to fabricate a flat metal bar at least 3mm thick and ~60mm wide. The bar should be long enough to pass completely under any top box and leave enough room on the Off-side to fit the antenna mount. This stops the antenna bouncing on the top-box and prevents an annoying sound at best, or a damaged top box and antenna at worst.

The flat bar is firmly bolted to the bikes frame using the top box mounting bolts. I drilled two holes the same diameter as the top box bolts and fixed the bar between the bolts and the top box mounting frame to ensure a good earth. As my top box frame is metal it also acts as a radial to improve the earth. The rig is dual band so I have gone for a solidly built dual band antenna, the Comet SBB2 (63cm long 2.5db/5db) is ideal for general round town work and the SBB4 (96cm long 3.0db/5.5db) for Raynet work/longer runs.

That's it. It works and I have had quite a few interesting chats with various other radio hams, not just locally but via the repeater networks literally all over the world and it always raises an eyebrow when you sign as “/motorcycle-mobile!”

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