Can you hear me now? Episode #2

Hello fellow 'radio heads',
I just came from a very interesting visit with Steve Hoehn of Banner Mountain Communications. Although I have some background in electronics I wanted to be sure of certain facts. The next couple of paragraphs will address some technical issues that may be boring to some. If you just want the bottom line please feel free to skip to the last paragraph. I think I have some good news to report there.

CAUTION: SCIENCE CONTENT

There are basically two ways to send data on a radio wave. The first, and oldest is what is called AM (amplitude modulation). In this form the information causes the strength of the carrier to vary according to the data, in this case a voice is impressed on it. It is simple and it works. But, virtually all of the natural background noise in nature is also of an AM nature. So lightning, spark plugs, generators, electric fences, etc. are also transmitting in this medium. CB radios are AM.

The second way is called FM (frequency modulation). In this medium the frequency of the carrier wave is moved up and down within a range that changes with the data. Nature for the most part does not do this. So by it's nature FM tends to have much less background noise than AM. Our club radios are FM.

The next thing to know is about something called wave length. If you could see a radio wave you would become aware that it has peaks and valleys that repeat within a given time and distance. The distance between these peaks is called the wavelength. It varies with the frequency of the radio wave. The higher the frequency, the shorter the wavelength. Who cares? Well, it has to do with how an antenna works. To be most effective a antenna needs to be at least one quarter wave length long. Other lengths will work, but at a much reduced efficiency. CB radio works at a frequency of around 27 MHz (27 million cycles per second) That sounds pretty fast, but at that frequency the quarter wave length of an antenna is about 102. That is about 8.5 ft. folks. What looks fine on a 18 wheeler does not look so great on a hotrod. And, how can you do that with a hand held? This is not to say that CB does not work at all, but the efficency is very much compromised by this fact of nature. Our club radios work on a frequency of roughly 465 MHz. At this frequency a quarter wave length antenna is about six inches.(.5 ft.) This is very close to what our club radios have.

GOOD NEWS NOW!

OK, all this technical BS means nothing if you can't use the radios as needed due to interference. Most of the complaints are about a repeating noise that has been blamed on a radio with a dying battery, or that is somehow out of tune. This is not the cause. Steve has tried to track this problem down and has failed to find a single source. It may be radar, it might be something from Beale AFB, maybe aliens. But the good news is that there may be a relatively simple solution. There is a feature called tone coding. What it does is tell your radio to ignore any signal it hears that does not have a 'secret tone' riding along. The tone is something that you can't hear, but the radio can. So when this mysterious noise occurs, the radio ignores it, because it does not have the secret tone.

The best part of this is that this feature is BUILT IN to our Kenwood radios. Steve says he will give us a special rate to make this work if we can gather up all our radios and bring them in. He estimates a cost of around $5.00 each. Pretty darn cheap to get rid of our main complaint with these radios. If there is a down side it is that we all have to do this, because without the tone your radio won't be able to 'talk' to the other units. They will think you are transmitting noise. Also, for those of us that have the older Radio Shack one channel version, the modification is a little more complex. However it is not a real big deal even for these. Our original radio guy that got us started with these radios just a happens to produce the module to make this work. I don't know the cost for that yet, but I can find out. Most of our members have the Kenwoods anyway, so there are only a few of us that need to go this route.

In conclusion, I want to thank Dave G. for investigating the problems we have with our radios. However, both Steve and myself feel that moving to CB would not be a better way to go. We have a good system, we just need to tweak it a bit. And it turns out that we may be able to improve our situation relatively easily.

By Lanny N. • Graphic by Ray Yedding.

Next month: About Our Club Batteries

Note from Dave G.: I contacted Steve Hoehn of Banner Communications. Unfortunately, he will not be in town for our Oct General Meeting. He will be able to give a presentation at our Nov. General Meeting. He hopes to be able to explain, in better detail, items in both my and Lanny's articles. (Dave G.'s article was in the Sept '09 newsletter). He can help us all understand what needs to be done to make our radios work together a whole lot better.

2009 Car Show Photo Albums • Loma Rica Car Show • Vintage Car Races
Geezer Picnic & Thank You Party • Pontiac Progress • Club Radios - Part II
Buzzards Movie • AB32 & AB118 Report • Calendar