During a recent visit to a local hobby store, I got an education about an important but often ignored tool of rc modeling – antennas. During the course of this blog, we will provide an overview of antennas and their applications for rc planes.
For all of the sophistication of antenna theory, the techniques for the successful operation of an rc model antenna are relatively simple. To gain further insight, we must define an antenna and how it operates. A transmitter antenna is a straight wire or telescoping pole device which converts an electric signal in the form of a radio frequency into an electromagnetic field. For successful operation, the antenna must be connected to the transmitter device at one end with the other end connection free. In the case of rc model planes, a receiver antenna is also necessary. A receiver antenna is usually a straight wire, which converts the transmitter radio signal and its associated electromagnetic energy into an electrical signal, which controls the aircraft. As with transmitter antennas, one end is connected to the aircraft, while the other is free from contact. Frequencies denote the number of times an event occurs within a given time period. Radio frequencies are stated in Megahertz, or cycles per second with one hertz expressed as one cycle per second. A radio band is a spectrum or range of frequencies designated by the Federal Communications Commission for a particular purpose. Most rc models operate in the 27MHz, 35MHz, 40MHz, 72MHz and 75MHz bands. Electromagnetic fields can be explained in the form of static electricity creating energy. However, the electrical charge traveling from the rc model transmitter contains more energy, traveling through space at the speed of light. The magnetic and electric fields change as the transmitter antenna frequencies change.
Directing the antenna for the best performance is another issue. When the hobbyist points the antenna in either a forward or direct vertical position, the antenna is often pointed at the model. If the model flies straight, there is usually no problem, but if the aircraft is performing a manuever it could result in a pause, from a temporary loss of signal. Some hobbyists even point their antennas toward the ground. By doing so, they lose the strongest part of the signal and limit the distance from which they are able to control the plane. An advantage of pointing the antenna to the side other than constant signal strength is pointing the antenna toward the plane results in more stress on the antenna from being continually flexed, which causes both more breakage and repair bills. There are also several troubleshooting procedures to make sure your rc plane is responding properly. The first and perhaps most obvious is to check the on and off switches, not just to make sure they are on or off, but to determine if they are in working order. Next, be sure the transmitter is set to the right frequency for the plane. Often this can be corrected by merely changing the crystals in the transmitter. Be sure both your transmitter and receiver batteries are at a full charge before flying. Ideally, they both should have an equal charge. Next, inspect the receiver antenna for proper installation with the transmitter antenna fully extended. Based upon prevailing rc radio frequencies, a transmitter antenna length of 28″ and a receiver antenna of about 40″ provide optimal performance for most rc models. Switching rc model and transmitter combinations is another way to isolate problems. These are but a few procedures to make sure the rc pilot has a trouble free flight.