What are the effects of communicating on VHF/UHF on a RMI's ADF needle?
NDBs in the U.S. transmit between  90 kHz and 535 kHz, and VHF is between 108 and 137 MHz. Of the VHF frequencies, the nav/com is only capable of transmitting between 118 MHz and 137.  

So aside from electromagnet interference, no VHF radio should transmit on a frequency that he ADF receives.