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Ofcom EMF Guidance for Aeronautical Radio Users - Prepared in Conjunction with AOPA

Ofcom have now published guidance for Aeronautical Radio Users in respect of compliance with EMF conditions for licence holders. This guidance comes after AOPA and other Associations raised complaints about the Ofcom consultation process that did not involve stakeholders from the GA community or even the CAA. AOPA and other Associations worked with the CAA to produce this simplified guidance for Aeronautical Radio users.

As anticipated, the guidance confirms that there is little or impact on the majority of Aeronautical Radio Users.

For VHF Radios:

These radios may either be permanently installed to the airframe with an external antenna or a handheld unit temporarily connected to the airframe.

They operate in the frequency band of 118-136 MHz and typically have power levels of less than 6 Watts for handheld equipment and up to 25 Watts for permanently installed equipment.

  • If you only use handheld equipment, you do not need to comply and do not need to take any further action in relation to your VHF radio.
  • If you use fixed equipment with an external antenna and a radiated power of 25 Watts, and you transmit for less than 25% of the time in any six minute period (i.e. less than 1 minute and 30 seconds), you do not need to comply and do not need to take any further action in relation to your VHF radio.

Ofcom expect that there should be very few situations where operators would need to transmit for more than 25% of the time. The CAA’s Radiotelephony Manual emphasises the need for clarity and brevity in transmissions.

However, if you consider that you may routinely need to transmit for more than 25% of the time in non-emergency situations, you should carry out a compliance check, as described in Step 2 of the guide.

For Transponders:

These devices transmit on 1090 MHz (in response to an interrogation from a ground station). Aircraft transponders generally have a nominal output power of up to 260 Watts, with a typical antenna gain of 3dB.

However, they transmit very short pulsed signals with a duty cycle of about 0.55% (i.e. it only transmits for 0.55% of the time). This means that the average radiated power of this equipment is in the region of 4-5 Watts.

Ofcom has calculated that, in the absence of a ground plane, the compliance distance for this equipment would be in the region of 26cm. However, the presence of an antenna ground plane will mean that compliance distances will be very small (typically much less than 10 cm).

In most cases therefore, you will not need to take any further action in relation to your transponder.

If, however, you:

  • do not have an antenna ground plane installed AND
  • the transponder antenna is located less than 26cm from a passenger who is a member of the general public,

you will need to carry out a compliance check, as described in Step 2 of the guide.

Other Radio Equipment:

If you have other radio equipment installed you will need to carry out a compliance check, as described in Step 2 of the guide.

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