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Is It True That Using 1.2 GHz VTX Will Interfere GPS signal? Need Advice Please

Hello guys, I need to do long range Surveillance (with Real Time Video Tx.) about 20-30 km within hills and mountain area. So this is a BLOS mission. Unfortunately in that area there is no internet/cellular signal available. To my knowledge the proper way is to use 1.2GHz Video TX with 5-10watts power output (or using expensive digital VTX system). But I read somewhere that this 1.2GHz strong signal from the VTX will interfere GPS reception. Anybody can advise me how is the best way to do this is?? Thank you.

I have no experience with VTX in aircraft but based on my experience with high-power rockets there is a very real possibility of interfering with the GNSS receiver. The higher power your telemetry transmitter the more likely you will have an EMC (electromagnetic compatibility) problem. I have seen this manifested as long time to acquire, or reacquire, position lock and a reduced number of satellites in the solution. The external fields can introduce timing jitter in the GNSS receiver which leads to uncertainty in the correlators and hence in position. Ground testing should show up any sensitivities to your telemetry transmissions. Remember to keep your Tx antenna as far from the GNSS receiver as practicable. Careful antenna placement will definitely help. Keeping transmission power down also helps, if you can manage with the lower power. The higher the power, the more problems you will see. I also suspect the cheaper units will likely cause more interference, but I don’t know for sure.

FYI, I am currently working on a system with 600mW at 1.3GHZ and 1W at 915MHz. They are on a 4" diameter rocket and the antennas are around 300mm from the uBlox GNSS Rx. They seem to be playing well together on the ground.

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