Band expanders in imported vehicles

Some people choose to fit a band expander in their imported vehicle to improve radio coverage, however these can cause problems. We recommend replacing the radio with a model designed for the FM band used in New Zealand instead.

Frequency range for FM broadcasting

The frequency range agreed internationally for FM broadcasting includes 88-108 MHz, and is used in many countries — including New Zealand. Japan, however, uses the frequency range 76-90 MHz.

Image shows the overlap of the Japanese FM bands available in imported cars and the range of bands this can be expanded in the International FM bands.

If you drive a used car imported from Japan it will probably be fitted with a Japanese car radio which, without modification, only receives some New Zealand radio stations.

Band expanders

In order to receive all available local radio stations, many people choose to fit a band expander in their aerial lead. Band expanders "shift" FM radio signals used in New Zealand to the frequency range used in Japan.

If you have fitted (or are thinking of fitting) a band expander in your car it's important that you read the following information:

Radio Spectrum Management (RSM) consider band expanders to be unsuited for New Zealand conditions. We don't endorse or encourage the use of band expanders, and we don't take them into consideration when planning and engineering FM broadcasting bands.

Problems with band expanders

If you own a Japanese second-hand import car that has been fitted with a band expander, you may experience problems with your reception. They have also been found to cause harmful interference to sensitive two-way radio systems at airports and other important radio infrastructure.

Degradation of your listening experience

If you own a Japanese second-hand import car that has been fitted with a band expander, you may experience some or any of these problems with your reception:

  • Wrong interpretation of frequency.
  • Distortion due to high signal levels (overload).
  • Degraded reception due to radiotelephone signals.
  • Intermixing of radio stations.
  • Radio may switch between signals, seemingly at random.
  • Blank-spots at some places on the tuning range.

The above is not considered "interference" in terms of the Radiocommunications Act as the degradation occurs within the receiving equipment.

You may even hear some of these effects on your normal car radio when parked near to a car using a band expander.

Harmful interference to other signals (EMC Compliance)

Band expanders have been found to cause harmful interference to sensitive two-way radio systems at airports and other important radio infrastructure.

We've undertaken laboratory testing of some band expanders offered for sale in New Zealand, and have determined that they may not conform to New Zealand electromagnetic compatibility (EMC) standards.

The supply, installation or use of interfering equipment may result in compliance action by Radio Spectrum Management in accordance with the penalty provisions of the Radiocommunications Regulations.

Radiocommunications Regulations 2001(external link)

Solution

The best solution — to allow full reception of all local radio stations without degradation or interference — is to replace your Japanese car radio with a model designed for the FM band used in New Zealand.

Talk to your local car audio supplier, or contact us for more information.