Motorcycle Mobile on the Hf Bands
he addition of some more controls to deal with when you consider the controls a rider already has to deal with, just might be the controls to cause a crash. So, operating in town just is not a good idea. Leave it to the police. Being a hood ornament on a Chinese gunboat with Cadillac written on the stern is no fun.
So, skip operations in town. Let us concentrate on the touring aspect of riding the open road. That is the best place to operate and the chance of getting squashed is lessened. Besides, being in the open is where you will get out the best any way. We will concentrate on open road hamming on two wheels.
Problems Lurking under the Seat
The biggest problem is IGNITION NOISE. Although with the installation of cb/am/fm radio combinations on the bigger machines like the Gold Wing, and the other similar class bikes of that size, the noise is there. If someone knows of a good way to do it, pass it on. Motorcycles are not known for having strong ignition systems, and my Yamaha TX 650A only has 10 kV out of the coils. The CX500 I had prior to this had nearly 18 kV out, as measured on a scope, but both have spark noise to rival the most ferocious thunderstorm ever known¼ more noise than a ’54 Ford, and covers the radio spectrum from dc to light.
Shielding is nonexistent on any wiring on a motorcycle, so the problem is there, and really bad. Unfortunately, there is only one diesel bike on the market, but it is a 250cc single, and not too swift, taking a mile or so to get to 60 mph and that is without a head wind and with a skinny rider on it. So, that option is out, for right now anyway.
One problem is the frequencies that are going to be the best for operation from a bike are the ones prone to being interfered with the most, namely 20/15/10 meters. Not that 40 or 75 meters are out of the question, but more on that later. Ever wonder how or why we got the noisy frequencies? Well, no matter, we are stuck with them and so we must make the best we can of what we have.
Another problem is, what will our transmitted rf have on the on board electronics? Since BMW and others have marketed their version of ABS on the K series, soon Yamaha, Suzuki, Honda, and Kawasaki will have some form of cruise control and there is no telling what a ssb signal will do to this sort of stuff. A 100-watt rf output transmitter is a lot more signal than a 5 watt cb, so, keep this in mind when installing a 100-watt mobile. Remember the problems that occurred when cars started to switch over to microprocessors. On two wheels it could be a real disaster to have either the brakes not work or to have full throttle turned on when you called CQ.
Most primary 13.5v dc systems now can handle the power of most of the smaller Icom 735 type rigs. The mono-band Dick Smith 30-watt rigs would have been fine as well as the Yaesu 707 class rig. These rigs are just about all anyone would like to have on a bike, but one chap (WA3MXO) ran a TS-430 into an NCL 2000 with a 2.5kw ac Honda generator in a trailer he was towing behind his Gold Wing. That is rather impressive for two wheels. In general, we should keep the power to reasonable levels to keep from badly overloading the primary 13.5vdc system on your bike and running down the battery. Headlights is a nice feature as is pushbutton starting since there are no kick-starters on bikes anymore.
Now, to more antenna-related things, namely what antenna to use. Just about any antenna you would use on a car will do, but, mounting it is your problem, since each bike is different and no two riders ever set their bike up the same. It will be a problem for some while others will not have too much trouble. Bear in mind the vibration and general pounding that a touring motorcycle is subjected to is a lot more than any car other than an off-road race machine or police car ever gets. Also, the possibility of dropping the bike is very real, so construct your mount accordingly. If you don’t ride alone, be sure your rider cannot contact the antenna under any circumstance. That might cause some friction in any relationship. Rf burns on the buns along with a 70-mph dragonfly between the eyes just might be more than any relationship could stand.
Assuming you have your rig and antenna mounted on your Cavalcade, Voyager, or whatever, the next thing is to tune up the antenna. Now comes the burr under the saddle blanket. You will have to find a way to hold up your bike with rider and everything configured just like you would be if you were on the road. No feet on the ground just like you were riding. Possibly the best way to do this is with plastic milk cartons under the crash bars and poly rope tied to the handlebars. Be sure to be in the clear as much as you can so nothing is likely to cause the tuning to change when you get on the road.
It really doesn’t help that the capacity to earth ground shown by a motorcycle is no where near that of a car, since the surface area of the underside of a motorcycle is less than that of a car. This will influence tuning at the lower frequencies, 75/40 meters more than at 20/18/15/12/10. So, tuning on the lower frequencies will be more difficult, but not impossible. Possibly the best way to do this type of operation is with an Icom 735 and the matching AH-2 automatic coupler, or similar automatic coupler. Putting the rig in a hard plastic saddle bag or trunk, mounting the coupler externally with a small control box for volume, tuning and ptt on the handlebars, or in the fairing, would get the rig out of the rain and weather and allow you to QSY without stopping.
There are several automatic antenna couplers made for the marine radios that would do the job very well, requiring only 13.5vdc and rf input, but, they are very expensive. Some of the military couplers such as the Collins 490T series will do also, but, they require some conversion, and the construction of a 13.5v dc to 115v ac, 400 cps power supply. They can stand a lot more power than the commercial couplers and if you wanted to use a Metron mobile kW, the coupler would not burn up when you fired up the rig on a different band and forgot to tune up at low power.
Remember, keeping your eyes on the rig is secondary to keeping your eyes on the road and the Chinese gunboats that are being piloted by myopic no-see-u drivers. So, plan your installation and operations accordingly, with emphasis on keeping the bike under control over operating the rig. You can always park and operate, but using your hide and motor to clean the pavement by sliding along it at 60 mph is not my idea of fun.
Operating the rig should be kept at a minimum as far as control usage is concerned. One idea is the use of a car cd adapter with your onboard stereo system to feed the audio from the ssb rig into the already existing audio amps, speakers, etc. Provided you don’t get any rf into things which will cause a lot of audio feedback. By doing this, you will be able to use the handlebar mounted controls that some of the touring bikes have. Vox operation is not a good idea, because telling the world the clown that nearly converted you into a pancake had a cocker spaniel for a mother isn’t considered good manners. Thus, ptt is the way to go.
Keep in mind these are only ideas and NOT explicit “do it this way instructions”. Every rider has his own ideas about his motorcycle and how things should be done on it. Just use the ideas here as food for thought, and go from there.
Originally posted on the AntennaX Online Magazine by Richard Morrow, K5CNF
Last Updated : 13th March 2024