Q Juan, KB3CJG, asks, “I have a problem with my dualband (VHF/UHF) mobile FM transceiver, a Yaesu FT-8100. When I install it in my car I cannot transmit. The voltage of my car battery appears to be a bit low (around 12 V, as reported by the rig’s built-in voltmeter) and the FT-8100 manual recommends 13.8 V. I have no problem operating at home using a 13.8 V power supply. How can I solve this problem?”
A It sounds like you have a bad battery, voltage regulator or alternator, or a “partial short” (a low resistance that shouldn’t be there) in your automotive electrical system.
Take your car to a mechanic and have your battery system
checked with your rig disconnected. If there is a problem, such as the battery not holding a charge, or a faulty alternator, get it fixed. My guess is that the mechanic will find a problem.
However, if everything is okay, then disconnect the automobile cables from the fully charged battery. Connect your rig to the battery and see if it operates. This will tell you if you have a “partial short” in the car.
If all of the above are good, then make sure that you have a good direct connection from your rig to the battery (no substitutes such as the fuse block or cigarette lighter!).
From QST March 2001
