Troubleshooting the VideoLynx 434
 
Here are a few hints that will help you solve some common problems.

Unstable Picture:

The Videolynx434 provides a 50 ohm antenna match. If you use anything other than 50 ohm coax to feed the antenna, severe RF reflections or high SWR may occur. This could result in the output amplifier of the VideoLynx 434 becoming unstable, usually resulting in a distorted received image. Remember the VideoLynx 434 is a relatively high power output device for its class. Therefore it is vital to provide good antenna matching. Supplying it with a properly matched antenna is critical. If for any reason you cannot supply a matched antenna system,such as the case of an R/C (model rocketry etc) type application, where you are constrained to using a small 1/4 wave piece of wire for an antenna, you may compensate for any video instability by adjusting the linearity control clockwise. This reduces the power output of the VideoLynx 434, which in turn will stabilize the picture by reducing the RF energy that is reflected back to the 434. However, this may come at the cost of reduced power output. Therefore, it's best to provide a good antenna system (50 ohm, at 433.92MHz) for optimal operation of the VideoLynx 434 .

The linearity/bias adjustment trimmer on the VideoLynx 434 is a very critical adjustment. This control affects both the video quality as well as RF power output. The nature of an amplitude modulated video signal is such that a video signal with lots of contrast will result in a lower power output level while a video signal that has less contrast will provide a much higher RF power output. Adjusting the linearity control fully clockwise will result in the lowest power setting with greatest contrast and vise versa. In order to obtain the highest RF power output while achieving good picture, adjust the linearity control to the most counter-clockwise position and then gradually turn the control in the clockwise direction just until a good quality image is received. This will be the optimum video to power output position.
 
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