Radio not transmitting at night?

[BABALU]

For some reason on 3 different occasions it appears that my radio is not transmitting at night. I can hear others but apparently nobody can hear me til I'm on the ground. Is this possible ? During day time flight everything is perfect
After 3 episodes I'm starting think something is up. Maybe my nav lights are causing this somehow. No problems when strobes or landing lights are on because I use them during daylight flights.

[xavierm]

What happens when you turn the nav lights on during the day?

[BABALU]

I will let you know tomorrow.

[BABALU]

Took my hand held and checked it out, It's the nav lights. Everything works perfect til the navs are on.

[FasGlas]

Check the buss voltage with the lights on, should be at least 14 volts. If you have plenty of voltage check the antenna cable.

[BABALU]

Originally Posted by FasGlas

Check the buss voltage with the lights on, should be at least 14 volts. If you have plenty of voltage check the antenna cable.

Voltage is fine and the antenna is fine because I transmits perfectly clear when navs are off and I can can hear incoming transitions when they are on its just that it won't transmit when they are on . I'm thinking that it may be a conflict between the push to talk and the navs somewhere probably at the buss?

[Flyingleap]

Measure the resistance of your "insulated" mike jack to ground. If it
is not zero but the value of nav lights resistance, we have the problem, but why? Each microphone jack should be insulated from ground but it's return to ground should be at the radio for noise reduction. What could happen here is if you short the mike ground to ground and turn on the nav lites, it blows the breaker, we at least have the right scenario. Hmmm John

[JDA_BTR]

Think about how your power is distributed too. When you key the mic you demand max power to the radio to transmit. With the nav lights on you may be drawing more current than you think. Or you could have a poor contact to the radio and the voltage drops across the connection in a high load condition. I would replace the radio fuse if there is one, and clean/reconnect the radio supply/ground as first easy steps. Then think about your load distribution. Your wire to the radio might be undersized; same for the nav lights.

[BobTurner]

One thing that would produce this behavior is if the ground side of the PTT doesn't go to ground, but to the nav light circuit by mistake. The lights have a low enough resistance to 'close' the circuit when no 12 volt power is present. Check the wiring.

[BABALU]

Thanks guys for the incredibly useful info. This will be my weekend project / challenge. Will update.