check all of the grounds.........relocate the coax or get some better shielded coax........Socaldmax would be the one who could answer these questions.......If he has not chimed in after while Ill call him. What type of box(power adder)?
Your either getting into your Quad box through the power wires or by direct RF pick-up through the air. Probably not much you can do about the Quad box, so focus on the CB equipment.
Step 1 - make sure you have a separate ground and +12V wires going directly to your CB amplifier from your battery. Do not use chassis as ground, use a direct connection to the battery for both ground and +12V. While your at it, make sure your CB radio itself also connects directly to the battery with two wires.
Step 2 - I assume the Quad box is located under the hood. Make sure the amplifier is not located in the same compartment. This should help some if their is any RF leakage coming from the amplifier chassis.
Step 3 - If this does not work, try moving your antenna around. Make sure it is mounted on top of the vehicles roof. If possible, get away from a "Magnetic Mount" antenna. You are most likely not getting a good ground with this antenna. Which leads into step 4.
Step 4 - Adjust the antenna to get the lowest VSWR.
Step 5 - Where did you route the coax from the amplier to the antenna. Keep it out of the engine compartment if that is where the Quad box is located. Keep the coax away from all vehicle wiring cables. The cheap RG-58 coax they use on most antennas does not shield very well. You may want to consider some sort of double shielded coax like RG-142 (should be 50 ohm double shielded equivalent). This should work for power levels to 100 watts.
Miles PH did you get this problem fixed? I have a small amp and may go bigger at some point, so I'm interested in what your problem is/was. I'm also wondering at what point the alternator in these trucks don't put out enough. That may or may not be the problem.
A mag mount is useless (electrically) at more than about an honest 150 watts or so, so these guys are right about your reflection levels. I date from the days of the Audio King, but a good whip like a Francis Amazer at the bed top works very well. The fact that your dead-key does it may indicate excessive carrier power; If your amp does 400 or more, your carrier power should not exceed 200 max. for am. I would be at 100-150 maybe. Hope this helps.
FWIW, I've been running 200 measured dead key watts for a couple of years now with no issues. I have a 1/4 wave whip mounted on my tool box. Thought it was 102 " though. The coax from the amp is the size of my thumb, that may help?
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