Batboard

Hi all

I have a issue between 45 watt VHF radio & CB radio ; When you transmit on the VHF radio it opens the CB radio transmit light ( Cobra 29 LTD Classic and Motorola Maxtrac 46 watts) \ Antennas are about 3 feet apart too !!!!

Any HELP would be appreciated !

steve w

First question, is it just lighting the TX indicator, or is it actually transmitting? If it's just lighting the indicator, why do you care?

Either way, what type of antenna is each, as in mag mount or hard mount? In either case, make sure all connections are clean and tight, make sure the coax is in good shape (no crushed places, no holes in the outer jacket, not cut, etc.), make sure the connector on the radio end is in good shape and properly attached, make sure it is a good quality coax, etc. If one or both are mag mount, you may be able to move them further apart, if room permits, and help the problem some, and I would recommend moving them further apart anyway, if possible. It would also be a good idea to make sure each antenna is properly tuned to the frequency it is being used on.

Hope this helps!

Just lighting the TX meter, all the connections tested good and no cable problems. At this point the antennas are as far apart as possible.
steve w

Hmm, interesting. It could be that the TX indicator, most likely an LED, is simply 'receiving' the RF from the VHF directly, as a crystal, which an LED is, is the simplest form of radio receiver. Try putting a .001 microfarad ceramic cap from the 'hot' leg of the LED to chassis ground, and see if that helps.

Does this happen with the CB off?

I like kf4sqb's theory. CB's are cheap and lack good filtering and shielding.

An LED is a diode, you have a nice diode detector there with the high band RF getting in the CB.

You can solder a 470pf to 1000pf cap from each lead of the LED to an adjacent ground and it should bypass the high band RF from triggering the LED.

You can also try placing a single cap across the LED pins/leads if you can't get a convenient adjacent ground.