Sometimes just having your radio in the field of another power source will create hum.  I tried putting my TS440 on top of its power supply and was transmitting hum on SSB.  Try moving the radio and see if the hum moves with it.

At 12:05 PM 4/27/2005, you wrote:
>the universal charger was probably very badly or not at all, filtered...a
>proper step down converter powering a radio of any sort should have filter
>capacitors inline to filter the AC cycle hum.
>I think allot of chordless phone bass units that are plugged in are using
>non-filtered converters in their wall warts, that causes hum to go through
>the transmitter and you can hear it on the handset while in a call.  Same
>would apply to any receiver plugged in, you will hear a hum coming out of it
>from somewhere if you plug it into a universal converter that has no
>filtration...if you switch to a more expensive filtered supply, hum can
>usually go away.
>73
>Colin, V A6bkx