I have a Pana NV-350B and generally am pleased with it. However, when I try to use an external microphone mounted on the camera hotshoe or an accessory bracket I record an unacceptable motor hum. The only solution has been to mount the mic on a separate tripod but this will be no good for on-the-move operation. I tried two different mic's (Sony and Sennheiser). Even one of those elastic cradle devices on the hotshoe did not remove the noise. Is this normal on this standard of kit? Any comments, ideas?