Tabb uses the 1.3 setup.... I myself use 2 iftron 5.8s and 2 lawmate 900s.... there is no reason you cant use 2 1.2s....as long as you put them both on different channels in that band.
If you do go with 1.2's, consider putting this filter on the RF output of the transmitters. It will reduce the amount of harmonic frequencies radiated that might interfere with the 2.4 Ghz RC data (2.4 Ghz, as you've probably figured out, is the first harmonic above 1.2 Ghz). Andy.
Hi Andy so your suggestion no matter what is if I use 1,2, 1.3 I should use the filter to avoid the chance if interference with the 2.4 of the RC Graupner Mx-20 correct, I am planing to use for now 1280 for the copter and 1258 for the gimbal on the ground they are working independently I have not try them yet in the air apart from the filter what do you think of this setup ?
I would certainly use the filter -- not because there will be problems, but merely to reduce the probability that there are. Yes, the concern is that your transmitting perhaps as much as 1000 milliwatts one harmonic away from the 2.4 Ghz receiver that you're relying on to keep your bird in the air. The use of the different frequencies is something that really depends on the quality of the transmitters, I'm afraid. The issue is how tightly confined the radio frequencies are to the frequencies you've selected and you'd have to measure those transmitters -- the further apart the frequencies are, the better, though. Sorry to be so indefinite, but there are too many variables and not enough equations.... Apart from which, you may know of "Osborne's Law" : constants aren't and variables won't. Andy.