We had to install a new voltage regulator in the alternator in one of our fire trucks. We can now not key the Motorola 2-way radio in our truck without the voltage spiking. Do you know what could be causing this and is there a way to block the radio transmissions from affecting the alternator?
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Re: 2-way radio causing voltage to spike
Hi and welcome to FixYa,
Your described problem indicates that the RF from the Motorola is being received by the electronic regulator of the alternator and is erroneously factored in as sensor/triggers. Simply stated, the RF causes the regulator transistor to conduct more allowing higher voltage output. There could possibly be two ways of addressing the issue: regulator/alternator side and/or the Motorola side. Things that you could try:
shunt a reverse protection diode across the output of the alternator to the ground;
install filter condensers on all the wires leading to and from the alternator;
wire a ground strap (not a ground wire) from the firetruck's - terminal of the battery to the alternator housing;
check/improve (lower down) the SWR of the antenna;
if you are using a magnetically mounted antenna, replace with a gutter mount or similar mounting brackets;
wire a ground strap (not a ground wire) from the antenna mount to the radio to the body of the firetruck to the alternator to the - terminal of the battery.
A ground strap is a flattened braided electrical wire unlike the common stranded auto electrical wire.
Pls post back results. Good luck and thank you for using FixYa.
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Check the battery or the power supply to the circuit, If there is not voltage to the main board this can be failure of the regulator. If not it can be fault in the control circuit.
Check the output of the battery eliminator.
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Check the input voltage into the radio while in transmit. The voltage maybe dropping as you go into transmit which causes it to drop into receive. That in turn allows the voltage to come back up. With your finger still on the PTT it tries to transmit again, etc. This could cause a feedback squeal and other symptoms.
If you have the schematics try to follow the voltage lines with a volt meter. If this is beyond your capabilities then I would suggest taking the radio to a service center or sending the radio to Kenwood.