[Elecraft] KX1 hum on 30 meter signal

[Andrew Moore]

I listened to my KX1 signal on 20, 30 and 40 meters today by using another receiver.  On 30 meters the signal sounds a little distorted, as if there's some kind of hum superimposed on the signal.  This does not happen on 20 and 40 meters.  Before I start digging in, has anyone experienced this on their 30 meter KX1?  The 30 meter option board is clearly a good candidate to check first...

Thanks,
--Andrew, NV1B