George you need a good RF shack ground, not a 8 foot ground rod but a good RF ground. A number of radials wires 20 or 30 on the ground connected to a plate near the shack and the braid of copper strap into the shack. Most hams now a days don't know what a RF ground is or why your shack Needs one... A lot of these strange problems go away once you have a nice low impedance RF ground..
Running a KW I cannot even get my field strength meter to register in the shack with my ground (50 -- 50 foot radials connected to a 12 by 12 inch copper plate and 1 inch copper strap to the rig and tuner..Marconi knew this over 100 years ago guys...Denny K8KAS..
George, Consider the RF shack posting, if your problem returns. MFJ makes a box to create the RF ground and it works every time. The ground rod is for electrical safety and lightning protection.