Nortek Security and Control KB

How do I increase the range on my radio receiver?

Sources of Interference:

In many cases, if you are having a problem with outside radio interference (RFI) that seems to have no source and no remedy, changing your receiver and remotes to something on a different frequency may be the only way to remedy the situation.

The frequency range that garage door and gate controllers operate on is listed as "government" frequencies.

These devices (openers) are unlicensed, which means that if a legally licensed transmitter is interfering with your remotes, and that transmitter is being operated properly, then changing your controller and remotes to a system on a different frequency is probably your best solution.

Before replacing your system, you need to find out what frequency range is affected. You could find this out by using a radio scanner (some call it a police scanner) that will receive in the 300 to 400 MHz range. You would need to scan this frequency range and listen for any signals.

Most manufacturers make controllers and remotes that operate in the 295 to 400 MHz frequency range.

Linear products are available in the following frequencies:

300, 303.875, 310, 315, and 318 MHz. There are other companies that make products in the 390 MHz range.

Without knowing the general frequency of the interfering signal, it would be impossible to recommend a system that will not be affected.

Correcting Sources of Interference:

While it is beyond the scope of these instructions to provide a comprehensive list of electromagnetic interference (EMI) solutions, the following are some examples and possible solutions.

Note: Radio Shack components are used only as examples, other sources of EMI filters are available.

Signal and control lines can conduct RF emissions and conduct RF energy from an offending source to the receiver. Radio Shack sells a series of snap-on ferrite filters (P/Ns 273-104 and 273-105). These often will clean up the signal if placed close to the source of the interference or at the receiver terminal strip. If possible, wrap several turns around the ferrite core before snapping the core shut.

Power line EMI filters / surge suppressors (P/N 61-2333) will reduce power supply noise from computers and other noise generators. Although it is less effective to place filters at the receiver, this may still help if the source of the interference is not known.

Telephone lines can also conduct RF signals and interfere with radio receiver range. A Radio Shack telephone RF Line Noise Filter P/N 43-150 may help to clean up the noise. This would be most noticeable when using a telephone entry system as the telephone line is routed into the housing, in close proximity to the built-in receiver.

Antenna leads may become corroded and dirty. They should be cleaned to be sure that they are making good connections. Poor antenna connections will cause the RF signal level to be reduced or the signals to be noisy.

For an isolated low voltage AC transformer, the clamp on ferrite cores may be effective, but wrap several turns around the ferrite material (P/Ns 273-104 and 273-105) before closing the clamp. Place the ferrite core as close to the power input terminal strip as possible.

If DC power (usually 12 volts) is being used, Radio Shack has a series of filters that are normally used for automobile radios and stereos. The power supply should, normally, be as close to the receiver as possible. For short runs of wiring, first try plugging the DC power supply into an AC power line filter. If that is not effective, try using the following noise filters: (P/N 270-030 (3 Amp), 270-051 (10 Amp), or 270-055 (20 Amp), depending on availability and required current ratings. In extreme cases, it may be necessary to use an AC power line filter as well as the above listed noise filters.

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