All posts for the month August, 2011

I’ve been working at quite a few rallies now, and one of the biggest things that a radio volunteer gets to do is listen.  When people listen long enough they start to think they know it all and can do a better job.  After Rally West Virginia I’ve kind of reached that point and humbly want to start compiling information into a more complete resource.  This is the start of that.

So, where to begin…..


Every rally that I have worked relies on the 2 meter amateur radio band for its communication.  Communication that is vital to both the safety of everyone involved and the logistics of running a rally.  The radio communications are usually directed by one individual called ‘Net’ that is typically located at the rally HQ.  Now there are lots of exceptions to both of those things, but I will cover that later.  The volunteers give information to Net who then disseminates it to the proper individual.  For example the 0 car will radio to Net from the finish that the course is clear and suitable for competition.  Then Net radios the stage captain, gets his assessment, then radios the start control and tells start that the stage is hot and to begin competition.

Order in this structure is absolutely critical for a smoothly functioning rally.  If one point needs to communicate with another point they either have Net transfer the information or ask to speak directly.

Most rallies also work through devices called repeaters.  Instead of each radio talking to every other radio, they communicate to a completely independent device on top of a nearby tower.  This device then repeats the information back out immediately, hence the name.  This allows for a much longer range and lets a spread out rally all work as one.

Like I said earlier, there are exceptions to all of these.  At NEFR for example each stage is run as it’s own self-contained unit.  Radios communicate using Simplex, where each radio just talks to each radio and works without a repeater.  In this case the Stage Captain or someone near the Stage Captain should be functioning as Net.

This leads us to hardware.  Almost all of use have gotten into rally due to hardware, but typically it’s automotive hardware and once a ralliest has his technicians license he doesn’t care anymore.

The absolute best mobile communication setup that one can have is a 75 watt 2 meter radio (like the Yaesu FT-2900) connected to a drilled NMO mount on the roof with a clean ground equipped with either a 1/4 wave antenna or a 5/8 wave antenna.  The quarter wave has 0 dBi of gain while the 5/8 has about 3 dBi.  The way to understand what this means is to imagine the radio being put out of the antenna as a donut.  The more gain it has the flatter the donut.  A flatter donut pushes more out the sides while having less height.  So a 1/4 wave is better for a more mountainous region.  For a general way to figure which is better if the target is over 45 degrees above/below you the 1/4 wave will be better.  If 60 degrees the 1/4 wave will be significantly better.

It should be noted that both of these antennas need a ground plane.  The roof of the car (or the trunk for those less willing) when tied in correctly acts as a ground plane.  It actually becomes part of the antenna allowing the maximum amount of signal to get out.

If one doesn’t want to drill, and use one of the many magnetic options a 1/2 wave antenna becomes needed.  The half wave doesn’t need to be coupled to the roof as a ground plane.  For maximum performance here the antenna’s whip has to be cut to ideal length.  This is called tuning, and a poorly tuned antenna can be the difference between putting out 20 watts or 65.  This is best done by someone who has the right tools and has done it before.

Another option is the HT or hand-held transceiver. These are mostly limited to 5 watts, and are great for listening and control working especially with a nearby repeater.  Some rallies can be conducted entirely with HTs, but there are not many.

Congratulations, you just read through Rally Radio 101.  I’ll think of more and add it later including radios in course cars, how to absolutely positively make sure your signal gets there, and additional means of propagation that should be employed by rallies.  If I made a mistake anywhere please comment or email me.