I got a strike finder and pretty much had the same experiance. I tried mounting on top, on bottom, different foils for ground plane, etc.
I found the hydaulic pump caused interferance, but was quite easy to figure out when that came on - I used a MU-metal shield & that helped some.
I finally created a fiberglass mounting bracket and a ground plane tray in the top part of the tail so the storm scope antenna was compltely electrically isolated from the aircraft. That also helped some.
I also found that the autopilot servos create a pretty substantial lightning storm. That is pretty messed up, since the time you NEED the storm scope the most, is when you are hard IFR and want to watch out for embedded T storms, and also NEED the
auto pilot the most during that time.
Basically I feel pretty much that I was ripped off. The funtionality of the storm scope is nearly worthless, and I was not advised of ANY of these issues until long after I had purchased the storm scope. My advice is get your money back, and put it toward a good subscription with WSI weather.
PS - anyone want to buy a slightly used storm scope?
Thanks
Doug Owen