30-year-old cobra 29LTD classic

It's a common problem with these Chinese cobra 29's today. Basically you just pull the bottom cover (cover with the speaker) off and with no coax connected, key the mic and turn VR6 until antenna light turns off. Put cover back on and and your ready to re-install radio.
If that doesn't fix the problem, then you may have a common mode current problem which maybe due to a poor RF ground with your antenna system.

 

Oops I need to correct this post, I was in a hurry when I wrote it. The Cobra TSB says to turn VR6 until lite turns off ( with out coax connected), but that's not totally correct. Because with no coax connected to radio, the antenna lite should be brightly lit up. So once the lite goes off, I turn VR6 the opposite direction until the lite comes on. First the lite is dim, so I keep adjusting VR6 until the antenna lite glows bright. After all it should be bright with no coax attached. Sorry for any confusion.