Odd ground loop problem and solution

I was befuddled for many days by an unusual ground loop problem. My mobile installation consists of an IC-7000, and a bugcatcher, properly mounted with a Breedlove ball on the left rear quarter panel. The power lead goes directly to a RigRunner box connected by a short, stout lead directly to the battery. Everything according to Hoyle, and no problems whatsoever for two years.

The car was in the shop for an expended stay after an accident. During this time, the rig was brought inside and worked well. Upon reinstallation, I began to notice an odd pattern on transmit, first on 20m, then on other HF bands, and finally on VHF/UHF. Power output would go down, ALC would go over the “red-lone” limit, but SWR stayed low as it always was where the antenna was matched. No problems on receive, and normal signal reports.

I checked everything I could think of:
•   Car repairs and body work were done right, and all doors, hood, trunk, etc were grounded.
•   Antenna mount was intact with everything tight and grounded.
•   All coaxes were checked and re-dressed
•   Power cables were inspected and checked out
•   Transceiver, coaxes and power cables were set up inside and checked out.
•   After a time, this pattern was seen even when the IC-7000 was directly connected to a dummy load in the car! And it was getting worse: the rig would shut down when a carrier was transmitted!

Obviously a ground loop and RF going where it shouldn’t. Then a flash of inspiration, after I realized that the only thing connected to the rig was the power cable(Duh). I pulled the battery lead from the RigRunner and connected it directly to the power cable for the IC-7000. Problem solved!

I think that the Power Pole terminals on the RigRunner had gotten dirty from all the time in the car shop. This led to a pattern of increasingly bad conductivity and impaired ground return. Tighten, tighten, clean, clean – always. I continue to appreciate the convenience of the RigRunner and Power Poles, but I will not forget about them!