~ Tips & Tricks ~
I am sure one of you reading this will fill in the blanks on "why", since all I can do is help with what! RC folks often use the words frequency and channel interchangably. That is fine, because most know what they are referring to. BUT when someone asks you "What channel are you on?", and you say, "You mean frequency?", that is when the fun begins.
What channel, er What Frequency, er...HELP!
The bottom line is that a channel number, or color, is assigned to actual frequency numbers with the supposed purpose to help people communicate better (channel numbers/colors are easier to remember than frequency numbers).
There is no correlation between channel numbers/colors, and the frequency numbers, which I find very amusing. Whoever did this, must be laughing insanely, knowing full well that none of us can remember what is what.
Bands - To understand the whole picture of frequencies, we need to start with Bands. Our radio systems are tuned to a certain band. Within the band are frequencies. The 27 mhz band, and the 75 mhz band, contain designated "Ground Frequencies". Therefore, these are the bands that boats, cars and other ground vehicles must use. The radio system that you receive with your boat is already tuned to a band, and you cannot change that. But you can change the frequency within the band by changing the plug-in crystals.
Those that fly will kill you if you sail your boat using a "air frequency" system, those in the 72 mhz band. Fortunately, you can't accidentally use a 72 mhz frequency in a 27 or 75 mhz band radio. Whew, thank goodness for little favors. But, I have talked to many RC flyers that want to use their radio systems in their boats - that is a No No! Obviously, a glitch in control in an airplane is far more catastrophic than in a boat or car. That is why the fly-boys are so crabby about what we lowly sailors are using.
Frequencies in a Band - We only use 5 frequencies in the 27 mhz band. They are listed below - and strangely they are given channel color names rather than numbers! Since there are only 5 frequencies, compared to the 30 frequencies we use in the 75 mhz band, the percentage of 27 mhz radios in the field is proportionately distributed. So if you have a 27 mhz radio system, don't think you are being descriminated against, there are not that many of them out there, proportionately.
Look into the Crystal Ball? Well, even though sometimes a crystal ball would be helpful, the frequency crystal is the heart of the frequency control program. This little quartz chip is what establishes the frequency in your system.
Crystals are little two-pronged plug-ins. They usually have a paper tag on them that tells both the Channel and the Frequency. How nice. Just to make it confusing, there is a crystal for the transmitter and another for the receiver - and they look exactly the same - BUT they are NOT interchangeable. I hear someone laughing at us!
The Transmitter crystal is marked TA, and the Receiver is marked RA. Don't ask. If the paper tag is missing, you may see an H in front of the TA, etc., printed on the metal crystal housing.
The transmitter crystal is usually mounted somewhere on the face of the transmitter, with a little plastic crystal holder that you just pull out with you fingernail. The receiver crystal is usually stuck into a slot in the side or end of the receiver.
Be very careful that the two prongs of the crystal actually go in the socket correctly. Sometimes they can be inadvertantly wedged in beside the socket where they feel like they are properly installed - but they are definitely not.
Crystals are fragile so don't drop them or keep spares rattling around in a tool box. Wrap your spares in foam or cotton.
Spare Crystals - If you travel around and sail with different people a lot, it is wise to buy a second set of crystals for your radio system. That way, if you show up and someone is using your frequency, you can change your crystals and go sailing. Bigger clubs often have loners.
Radio Tune & Performance - As mentioned, you can change the frequency of your system (within the Band) by changing the crystals. Many believe that the radio is tuned to the crystal frequency and that if you change your frequency crystals very far from the one the radio came with, that the radio will not perform. The fact is, in most of the inexpensive radio systems that we use, the reduction in performance is less than 2% for the entire range of frequencies! So don't worry about putting channel 82 in a radio that came with channel 63 - not a problem.
Please note - You cannot use a 27 mhz frequency crystal in a 75 mhz system and vice versa, even though the crystals look the same, fit perfectly, etc.
Band/Frequency Designation numbers - Note in the chart below, that the frequency number begins with the band designation number followed by a point (.), and then the frequency number. Therefore Channel 65 is frequency 75.490. Isn't this fun? The 75 is the band number, and the 490 is the frequency designator number. You would not believe how many people think their frequency is either 27 or 75 (the band number).
Yes, I know, the first frequency in the 27 mhz band starts with 26! How rude - just when I was catching on too.
As I said, print this little chart and put it in your tool box, on the wall, in the car, wherever, because, believe me - no one knows these things by heart - or if they do, they are probably dangerous to be around.
Channel flags?? - I thought you would never ask. Most of our boats come with a channel flag. If yours is a 27 mhz radio system, then you get a colored flag that you can attach to your antenna.
If you have a 75 mhz radio system, then you get a kit! Why me? In the kit are all the numbers. You chose the CHANNEL number you have, install that number in the plastic holder, and then you snap it to your antenna.
However, at most sailing venues, we don't use the flags. Most clubs use a pin system, or some other method to make sure that no two people are sailing on the same frequency. More about frequency control systems in the club management section.
Well now - I think I have told you more than you ever wanted to know - now you can go sit in the corner and suck your thumb while that insane laughing goes on in the background.
~ Tips & Tricks ~