Trig Avionics Limited

The requirement for 1090ES equipment on aircraft to have class B1 transmitters represents an unnecessary burden on smaller aircraft. Existing transponder carriage rules allow smaller aircraft (currently based on operating speeds and altitudes) to use 70 watt non-diversity transmitters. This is proven to give adequate coverage to ground radar receivers and to airborne collision avoidance systems. The same will be true of 1090ES ADS-B transmitters; for a small airframe there is little advantage in a diversity installation (because the opportunity for physical shielding by the aircraft itself is limited) and there is little advantage in higher power (because the lower airspeeds mean that the air-to-air service volume need not be so large). Since 1090 MHz is already a "congested" frequency, there is merit in keeping the transmitted power as LOW as practical, and therefore lower power transmitters should be encouraged rather than prohibited.