First, an explanation... To get the show (well, the COMPPA crew) on the road (to get the new transmitter up and running), I just quickly put it on the shelf, connected up the power cable, the feedline to the antenna, the audio input, and a ground wire, turned it on and ran with it.
Reflected power is a measure of how much power is not going out of the antenna, but instead reflected back down to the transmitter. This happens when the tower is not exactly tuned to the feedline...50j0 in electrical terms. That temporary transmitter setup was working OK, but there was about 45 watts (out of 1,000) being relected. There's a snazzy monitoring circuit in the transmitter which tirns it off whenever the reflected power gets too high. While that 45 watts was passable without any program on the air, in AM broadcasting, that transmitted sound adds to the power being fed to the antenna. We were finding that loud sounds actually shut down the transmitter!
So, this morning, I changed the tuning on some of the coils in the Antenna Tuning Unit...a metal box at the bottom of the antenna tower. In this I had guidance of data from previous trips, arrived at with lots of help from Grey Haertig and a generous donation from the folks at Kintronic Labs. My second trial hit on the "sweet spot"...the point of no measurable reflection...How sweet for the transmitter!
Now we should be able to accommondate anything that comes down the tube from the studio. There's still terrible distortion especially in the night, especially with the "Resistencia" feed that comes from Radio Globo. It's unclear whether that's due to operator error, some type of interference -- intentional or otherwise -- or a mal-adjustment of the limiter at the studio -- or a combination of those -- but the sound is bien feo, actually unintelligible at times. So, um, there's more work to do....
And that was written on Wednesday. This is Friday and with some work it sounds a lot better and is better installed. Some pictures..........
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