Bicycle Portable—Mark Ⅳ

The fourth version of my bicycle portable setup initially consisted of a Diamond NR770HNMO (NMO mount) 2m/70cm radialless antenna (3.0/5.5 dbd) mounted directly to the rear rack of the bike. (Since this configuration lasted less than one day, I am not giving it a separate version number.) The cool thing about this method, however, is that since this antenna has a very nice fold-over feature, you can fold the antenna forward, to be in-plane with the top tube of the frame. This enables you to fit the bike anywhere it could without the antenna, and to mount it a little more easily.

However, I wasn’t all that satisfied with the signal improvement I achieved (I was too close to the antenna and its base was even a little lower than the HT’s antenna when mounted to the handlebar). So I took an old telescoping fiberglass pole (formerly part of a tree pruner), cut several inches off the bottom of the outer pole and several inches off the top of the inner one (to avoid cutting off the spacing ring at the bottom of the inner pole), mounted the antenna to the top, snaked the coax down the hollow center, and then attached it to the rear rack with a pair of hose clamps.

It’s hidden by the pole, but the vertical support for the rear rack is the mouting point—all it took was two hose clamps to make the attachment secure.

Collapsed, and with the antenna folded over, the highest point of the setup is 78″—with the pole fully extended, the top of the antenna is up at something like 12′–14′. When the pole is collapsed, I gather up the excess coax and loop it through the bars under the seat, securing it with the strap at the front of the luggage rack bag.

Fiberglass pole retracted, antenna folded over. Heighest point: 78″.

Fiberglass pole retracted, antenna in normal, upright position.

Fiberglass pole extended, antenna in normal, upright position.

Another update to this version is the addition of a proper foam windscreen to the microphone boom. I used RadioShack Catalog # 43-2004, which also contains a replacement earpiece cushion, which might be useful in a future project. Of course, Mr. Murphy got me here—I had recently thrown out some old telephone headsets that I didn’t care for any more, including a Jabra EarBoom that had horrible audio and a horrible fit, but a windscreen that would have been perfect.

My Kenwood TH-F6A is mounted to the handlebar, and connected to a PTT button epoxied near the right hand grip.