I recently built a vertical. It's 6M radiator, a coil, and 1.2M more of radiator. It sits on my roof, which is metal, and acts as a ground plane (GND from the feedline is connected to it). There is a choke right at the feedpoint. The impedance is matched (with a LC circuit) from 36 ohms to 50 (49.9, for a SWR of 1.02:1 according to my VNA).
But whenever I transmit more than 50W, my internet and the neighbor's, drop. Sometimes it's a small packet loss, other times is continuous over several seconds.
This doesn't happen when I use the dipole.
The dipole is located about 15M from the street (where the cable companies cables are located, overhead), and the vertical is only 5M away from it. My cable drop rests on the metal roof that acts as a ground plane (I lifted it about 50cm but nothing changed).
What can I do to avoid this situation?
I also have a problem with strange interference near 145mhz that doesn't go away even when the power goes out. I suspect it's CATV related, so I'm thinking a leaky CATV amplifier is causing interference, and I'm causing interference to it as well.
I tried choking the cable to the modem but nothing changed.