Monday, January 3, 2011
Satellite Antennas, Continued!
I spent part of the New Year's weekend moving the satellite array from the testing location (next to my garage, between two houses) to it's more-or-less final location in the backard (now between four houses!).
The new location gives a little more view of the sky -- it's pretty clear to the east and west (views down to about 10 degrees), and is limited by my own house to the south (about 18 degrees) and a towering 2-story neighbor's house to the north (about 23 degrees).
The antennas are the same as I used during testing -- a 4-element Arrow for the VHF side, and a 15-element Diamond for the UHF side. Both antennas feed to ARR pre-amps mounted on the mast; I keep the UHF pre-amp powered on all the time, but only intermittently use the VHF pre-amp since there is so much VHF noise in the local area.
The platform that the antenna sits on is built from 2x4 redwood and concrete block pylons. Pictures below!
I also modified the Yaesu G-5500 rotator controller to improve its accuracy. I had found that the controller sometimes had a drift or error of around 10 degrees, and searches on the internet indicated a cause of this problem could be the 7806 voltage regulator inside becoming unstable and oscillating. I checked out my regulator with an oscilloscope, and found that it was indeed oscillating by up to 100 mV at around 5 MHz. To solve this, I added a 0.1 uF tantalum capacitor directly to the bypass capacitor (0.01 uF) that's installed on the regulator output. This removed the oscillation, and now the rotator controller's accuracy is dead-on.