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Corey

Two TX on one aircraft...

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In my continuing hobby-level experiments I tried something today with crummy results that seemed kind of odd and I can't figure out what was going on.

I used both a 500mw 900Ghz TX and a 250mw 5.8Ghz TX on the same heli, mounted about 4" apart, both with the stock whip antennas facing straight down to the ground. My thinking was that if one frequency was not getting decent reception for whatever reason the other frequency might work fine. The wiring from the camera up front was spliced to feed both TX units and I ran all three devices from one 3 cell lipo, separate from the lipo for the heli's power. The two ground receivers were connected to an Oracle diversity unit and the resulting output was a fast flicker from with the image from one frequency shifted slightly out of registern with the other. The 900Ghz receiver was pretty standard with an 8dBi patch antenna and the 5.8 receiver was a Yellowjacket Diversity receiver with two 8dBi patch antennas. When I manually switched the output from one receiver to the other the image was indeed shifted. I'm no rocket scientist but it seemed very odd to me since both receivers were using the identical video signal (weren't they?). Needless to say, the heli never left the ground and I guess I won't be trying this again.

Any comments? Would it possibly have worked with both TX on the same frequency? Also, while I'm here... Has anyone used the DMD long range fpv equipment with better than usual results and is there any where you can get English documentation for their product?

Corey

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If you are seeing slightly shifted images then that is not normally a problem. However, it sounds like you have connected the camera in parallel with both video Tx's without the required buffer/amplifier to ensure video levels are maintained. If that is what you have done then you will invite problems and will usually freak out the Oracle because the video levels will be non-standard.

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