I operate a low power FM radio station. I have always had issues with high SWRs. Recently I have purchased a new transmitter, new antenna, and new 100 ft cable from the same company assuming they would work well together.
To test the system, I mounted the antenna as high as I could reach on my radio tower (about 5 feet). I had no trouble broadcasting at 100 watts at 5 feet.
I am in a very rural area, so it took some time but I found a tower climber to come out and mount my antenna on top of my tower. Now the antenna is at a height of 75 feet. Same antenna as at 5 feet, same cable, same transmitter. However, now that it is at 75 feet when I go above 30% power or 30 watts my SWRs become too high and the transmitter shuts off to avoid meltdown.
Any idea why it would work just fine at 100 watts at 5 feet, but won't operate above 30 watts at 70 feet? Could something be wrong with my tower?