Nice to meet you Alan. The short answer is that if you are transmitting on the lower frequencies, a few feet seperation (a few multiples of wavelength) and on low power, it should be OK. If not transmitting, no problem at all although a few feet seperation would be advisable - it wouldn`t look so cluttered!! I`ve several aeriels on the same mast and transmit on several amateur bands, including 1296Mhz (23 cems), but following the rules, there is about five feet from the 23 cems aeriel to the Radarbox twig and only run fairly low power. Never had any interaction between 1296Mhz and 1090Mhz and find the Radarbox pretty well bombproof. Hope this helps, best of luck. Roger PS, just been informed that the aerial mentioned is for receive only so forget all the info on transmitting !!