Today was a nice, sunny day, with temperatures in the 40s, so I decided to measure the power drop along the coax from my 1296MHz power amp to the feed. The PA is at the closest indoors site to the dish.
I am measuring 520W going into the 35 feet or so of LMR900-DB that takes the signal to a junction box mounted at the antenna mast. There, I measure 420W remaining, which go into 27 feet of LMR600-UF to the feed (mast + rotor loop + cable to reach feed on 12 ft dish). After that much cable, barely 320W are left to go into the septum feed.
The numbers check out with the expected cable attenuation, so I understand that I’m simply experiencing normal cable loss. However, loosing 200W to heat the ground bothers me, so I’m looking for ways of increasing the power that reaches the septum feed. I’m first considering ways of keeping the amp indoors, but I’m afraid that I’ll ultimately have to put it all at the mast and use a hanging cable loop straight to the feed to minimize losses.