Factory BMW CB Antenna

[kbikerider]

I have the BMW CB Antenna with a Baehr audio interface and a Midland 75-820 CB in the oddments box. I was on a long trip using the CB when the following problem suddenly occurred. When I press the PTT, I get a shrill tone in the helmet speakers and also transmit this tone. I have traced the problem to the antenna mount. If I remove the antenna from the mount, it works fine. If I leave it in the mount, I get the tone. I have searched this and other forums, but found nothing similar.

Thoughts and suggestions?

Thanx in advance.

[djfalkenstein]

It is likely corrosion at the base of the antenna.

[kbikerider]

Well....I had some time today to address the problem. Everything I have read blames grounding. I removed the antenna bracket and found some corrosion between the bottom of the bracket and the bike frame. These are effectively 3x4 inch plates with no paint. I used vinegar and removed the white corrosion. I then took a wire wheel and brushed both plates to a shine. Upon reassembly, I ran a ground wire to one of the 4 bolts that hold on the antenna bracket. No more shrill tone!!!! I then replaced all the panels, parts, and top box. I tuned the system on one more time and there was the tone again. Not quite as shrill or loud.

Next time I will take all the parts, panel, and top box off and test after the reinstall of each part.