ham radio noise in 94 'burb

[Lug]

After setting for 2 years I finally got my 94 K2500 suburban running again. Now I have two different noises that my 2 meter radio is picking up. The odd things is that it seems to be only on 147.300, one noise is static and the other is an alternator type of whine, and both noises appear on both the Yaseu that is wired to the truck and the HTX-202 that isn't. As the drive progresses both noises go away. The alternator type of whine is vehicle speed related as it is not present unless the 'burb is in motion. Any suggestions?
Justin

[GMC Hauler]

After setting for 2 years I finally got my 94 K2500 suburban running again. Now I have two different noises that my 2 meter radio is picking up. The odd things is that it seems to be only on 147.300, one noise is static and the other is an alternator type of whine, and both noises appear on both the Yaseu that is wired to the truck and the HTX-202 that isn't. As the drive progresses both noises go away. The alternator type of whine is vehicle speed related as it is not present unless the 'burb is in motion. Any suggestions?
Justin

When you start up the sub, the batteries are more depleted from starting, thus the alternator works harder i.e. larger field and more EMI. As you drive, the batteries become charged, less work needed by the alternator, field strength goes down and EMI also takes a dive.

There is a magnetic pickup (reluctor wheel) on the output of the transmission, that sends a signal to the DRAC (digital radio adapter, or something close). On my vehicle is is above the blower motor. This converts the pulses from the reluctor wheel to something the ECM can use, your speedometer can use, and the speed controlled volume on the radio.

You could try a filter or insulating the wiring for the reluctor wheel with foil (temporary), maybe even unplugging it, but this will make drivability difficult and definitely set a code. However, it could be done for diagnostic purposes just temporarily.

KG4FKS

[Lug]

Something I hadn't thought of until yesterday is the fact that I have a mismatch between the prom that is currently in use and what it is supposed to be. Bill Heath had asked if I had any driveability issues with the combo of pump, prom, and the rest of the truck and I didn't consider the radio noise until now. I won't be able to test this out until the new pmd and prom show up. I was leaning towards the abs creating one of the signals, hadn't thought about the speed sensor stuff for the speedo in the tranny.
Justin