Ham Radio Forum

Hi, i want to know how to measure freq. of any external radio wave switch??

Thanks.

What radio wave switch are you referring to? Are asking about the frequency at which radio waves switch polarities or about some type of switch that somehow controls radio waves?

hi, i am asking for switches which are used in locking car by RF control ( some thing like auto cob).

reply.......!!

Someone else probably didn't answer your question sooner, because you didn't provide enough information to enable a short answer. The answer to your question depends on whether or not the approximate frequency is already known, the frequency measurement accuracy required, the frequency measurement speed required, the technical knowledge of the person who will be making the measurement, the types of test equipment that are available, or if suitable equipment is not already available, the amount of money that is available to purchase equipment. An entire book could be written to adequately explain all aspects of those issues.

If the approximate frequency is not known, the first step is to determine that before proceeding with precise measurement. There are a variety of ways to determine the approximate frequency. Devices that emit RF energy are regulated by government agencies in each country. They assign frequencies or bands of frequencies that can be used for various purposes and their frequency assignments are published publicly in most cases. In the United States and Japan most automotive radio remote control devices operate at a frequency of 315 MHz, because that frequency has been assigned by regulatory authorities in those two countries. Similar remote control devices in Europe generally use 433.92 MHz, but the 868 MHz band also has been authorized to meet the growing demand for such devices.

If the approximate frequency cannot be determined that way, it can be estimated by someone trained in electronics from antenna dimensions and various electronic circuit design clues. It also can be determined using various types of measurement equipment, such as spectrum analyzers or special radio receivers that are capable of tuning over very wide frequency ranges.Spectrum analyzers will provide the approximate frequency quickly, but they are expensive (many thousands of U.S. dollars). Special radio receivers that are capable of tuning over wide frequency ranges also are expensive and frequency determination by that means can require a considerable amount of technical knowledge and time.

If the approximate frequency is known or can be determined, more precise measurements can be made using specialized laboratory test equipment designed for the purpose. The best type of equipment to use depends on many factors, including the frequency range, the required measurement accuracy, the user's technical knowledge, etc.

However, if you have asked about this with the hope of constructing equipment that will give you access locked vehicles, you should know that in addition to that being illegal, control frequency knowledge alone will not give you access. Automotive radio remote control devices use digital codes that are not easy to defeat. Knowledge of the remote control frequency is about as valuable as knowing the type of key that will fit into a mechanical door lock. Knowing that is a long way from knowing how to shape the key so it will open the lock. The same is true of knowing the RF frequency used by radio remote control devices.

Roberto