[Yaesu] FT-897D transmitted noise

[Paul]

A local friend and myself have recently acquired FT-897Ds. We like the 
radios but have noticed a peculiarity with them. On SSB there is a 
background noise being transmitted. It sounds a little like another 
radio is on in the same room tuned to the same freq with the volume up 
just enough to cause a little feedback. It is most noticeable between 
words or any time there is silence while the PTT is still pressed. We 
hear it on both of our radios but not on other friends radios here 
locally. For  that reason we don't suspect that it is in the receiver. 
Raising or lowering the mic gain has no effect. Changing transmit 
filters does not change it. Engaging the DSP mic EQ does nothing for it. 
Shifting the transmit carrier is no help. Any body run into this before?
Paul, N5PS