On Fri, Aug 13, 2004 at 11:49:42AM -0700, Bill Swingle wrote: | But, in my experience. Most any antenna designed to be shorter than the | factory monopole will Decrease signal. The R/C site agrees with this and | claims a minimum range reduction. No surprise here.
Right-o. Probably the best receiving antenna for a plane would be a dipole with an electrical length of 1/2 wavelength (1/4 wavelength per side.) But this would only be marginally better than the half dipole that most receivers come with, and would require that you open up the receiver and figure out where the second wire should be connected. Probably not worth messing with in most cases. Now, there is some room for improvement by making sure that the antenna's electrical length is exactly 1/4 wavelength, as most antennas seem to be sort of close but not right on, but even doing this assumes that you know that they don't tune the antenna internally somehow. The same goes for transmitter antennas -- the manufacturers seem to be sloppy about the length, but it could just be that they tune for whatever antenna length they can get cheaply, and so adjusting the antenna length would be a bad thing. It all depends. You can get antennas with high gain, but for general R/C use high gain is bad. A high gain transmitting antenna sends most of it's signal in one direction -- which is great, as long as the antenna is pointed in the right direction. If not, things are *worse*. Receiving antennas work the same way -- if they have high gain, that means they receive best in only one direction. (Even a dipole has some gain, but it's low.) But ultimately, none of this matters because most of the time we have more range than we need. With standard equipment you can get 1.5 miles of range but probably can't see your plane at much over 0.5 miles away, so it doesn't matter. Unless you're trying to break altitude records, you don't really need to muck with your antennas, and you can even get away with installing less efficient but smaller antennas, or by not stretching the antenna straight out, stuff like that. If the plane has a foam wing, and you aren't covering it with carbon fiber or foil or some other conductor, just use an exact-o knife to cut a shallow trench (just one cut, just deep enough to bury the antenna) out on the wing, and spread it apart and stuff the antenna into it, then cover. You probably won't even know it's there. If you have to, you can double the antenna over itself, or turn at a 90 degree angle, but do be aware that things like this will reduce your range a little, so do it as little as possible. Don't ever cut the wire, unless you plan on fixing it later -- changing the length away from the 1/4 wave length will really affect your range. If you ever remove the receiver, cut the antenna off and leave it in the plane, but make a note of how long the part that was cut off was so you can make a replacement antenna, and so the new receiver knows how much antenna to cut off in order to use it. For your replacement antenna, all that really matters is that the length is the same. It's also smart to use stranded wire, because as was already mentioned, it's much more resistant to breaking. But beyond that, thickness, material, etc. don't matter much. Solder it on to make sure there's a good connection. -- Doug McLaren, [EMAIL PROTECTED], AD5RH For adult education nothing beats children. RCSE-List facilities provided by Model Airplane News. Send "subscribe" and "unsubscribe" requests to [EMAIL PROTECTED] Please note that subscribe and unsubscribe messages must be sent in text only format with MIME turned off.
