So I do a lot of bicycling, and I work the larger events from my bike (typically chase vehicle for marathons or triathlons. The guys at the back are usually not too fast for me. Finding the LOST folks is more challenging). This usually means two handhelds, one for my voice comms, and one dedicated to APRS.
Unfortunately, I can only get one mobile antenna on the bike, so the other is a rubber duck (one with more gain than what comes with the radio). This means that we have times when either my voice comms are questionable, or we lose the APRS telemetry. To fix this, I came up with a plan to put TWO mobile antennas on my bike.
I’m using an SBB-5, which is 1/2 wave on two meters. This eliminates the need for a ground plane or counterpoise, but means I really shouldn’t be on high power on 440. I have it on a UHF mount, which is stuffed into an old water bottle. For the event, I place it in the bottle holder on the back of my good bike pack, slide it all on the rack, and secure the co-ax.
Slide it on the rack? Yep. The pack in question is a Topeak MTX system. The bottom of the pack has a widget that slides into the rack (which is made to handle it). It clips on the front to remain secure. Easy on, easy off. Great for my morning commute! so what I plan to do is make (or rather, have my metalworking brother make) an aluminum piece shaped like the widget, so I can mount the antennas directly on that.
My big question is whether to just make it an antenna mount and use a regular pack (which is smaller, but I would worry less about having it damaged), or try to replace the plastic widget with the new one on the main pack. The latter isn’t as easy as it seems, since everything would need to be counter-sunk somehow, and I’m not sure the old one comes off in a manner that won’t just break it.
At any rate, when done, I would be able to have TWO UHF mounts, both firmly secured to the bike, so I could get good performance from both radios. Sadly, these things would be ridiculously close together, and it might be that this just won’t work well. But the only way to find out is to try it.
Some of the more radio-savvy among you are saying, “Listen, you idjit, the Kenwood D72 does both!” Yes, it does. But my bike rig includes the Pryme Blu — a Bluetooth PTT switch. This allows me to use the radio without taking my hands off the handlebars, and without being wired to the bike in case I have to get off the bike in a hurry. Unfortunately, the unit I have doesn’t work with the D72. Once pressed, the PPT doesn’t release, and the radio transmits until the timeout is reached. It works quite well with my F6A and my Wouxun (bought used because it rained for 7 hours at the last marathon, and I needed a cheap spare).
At any rate, some pictures below before we start the project!