Posted: 7/4/2011 3:43:59 AM EDT
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OK, My brain is frazzled on this one! Yaesu FT-100D Mobile install with separation kit running a little tarheel 2. Power wire is running straight from battery to radio with roughly 12-14ft of 10ga.
When the vehicle is running the audio is fine on all bands. With the vehicle off the audio is all garbled and I can see my signal fluttering and hear it in my ext speaker. This is only of HF and with the vehicle turned off! Once I start the vehicle it is fine. Now just for a few seconds once I turn the vehicle off the audio is fine then it starts doing the weird stuff again after a few moments! Am I having some kind of significant voltage drop that would cause the feedback? I have torroids in the power cord next to the radio, one in the mic cable next to radio and one in the coax feed line next to radio! I have ground wire on the - side of the power lead at the battery and one close to the radio. I am clueless! |
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Just to confirm, you're running both a power and ground wire from rig to battery? (If not, you should. Don't rely on the vehicle ground.)
Also to confirm –– transmit audio, or receive audio? I would agree that you need to measure voltages (or better yet, put a scope on the power) to make sure you're getting clean power. If it's transmit where things are going weird, you're at peak current draw, lower the output power and see if this changes things. I've had a flaky battery be fine at 20W output and go crazy to 100W. It's possible there's a power relay in your vehicle's electrical system that disconnects something when the car isn't running. It's also possible, and I've had this happen to one of my rigs, that your radio is providing the ground for some equipment in the car (this is why the negative lead is fused, BTW.) Isolate the radio from the chassis ground and disconnect any local ground wires to the radio so you only have +/- back to the battery, if need be disconnect the radio from the mount if the mount is grounded to chassis. |
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Sounds like your vehicle battery is toast, dropping voltage rapidly after the vehicle is shut off. Maybe even has a shorted cell. Take a voltmeter and monitor the voltage after you shut the vehicle off.
All of the previous suggestions are good too, if you find that the battery voltage is still sufficient. |
