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Adjusting transmitter module

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Hi there. I've been at VR flying for a while now, but find image quality and dropouts a persistant problem. OK, here in the UK I'm limited to 10mW, but even close up my CX161 cam disappoints across a radio link. I've never achieved anything like the quality of the videos e.g. on the RC-Tech website. I suspect poorly-adjusted transmitters and/or receivers are in part to blame.

See the attached image - it's one of those teeny 2.4GHz transmitters from a Swan combined camera/Tx. When I connected it to my CX161, it worked, but the image looked 'over-exposed'. When I looked at the board:

- By adjusting Trimmer 2, I can adjust the image 'exposure' and correct this to look the same over a wireless link as the image obtained from the camera's output direct.

- By adjusting Trimmer 1, I can adjust the image quality in a manner that appears to adjust the amount of sort of 'interference lines' on the image and their orientation (like a grill superimposed on the image, the pitch can alter, as can the rotation).

After adjusting, things can take a while to settle (perhaps I should use a non-metallic trimmer adjuster?); and it's really quite difficult to set things for an 'optimum' image, especially as the two settings interact :blink:

Does anyone know enough about these 2.4GHz modules to tell me:

1. What these two trimmers are probably actually doing?

2. Is there a simple way to align them for an optimum picture?


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The red trimmer1 cap changes the VCO reference voltage, which changes the transmit frequency.

The trimmer2 resistor adjusts the composite video signal level.


Freq Cal: With the Rx running at room temperature, adjust trimmer1 for a stable and reliable image. If there is a tuning knob on the Rx, it should be set to its "neutral" position (probably centered).

Video Level Cal: With the Rx video driving a 75 ohm load, adjust trimmer2 for a standard 1V composite signal on the output of the Rx (o-scope required). The camera should be looking at a fairly bright white light source during the video level adj.

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Thanks Mr RC-Cam! So tricky to get this sort of info from anywhere else!

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