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Testing condition:

Tests are taken from a roof top in Burbank, California.

When the tests were conducted, they are done very quickly. There is a receiving receptacle above the rotator that allows switching antennas with no tools. This is very important as reception/weather conditions can change quickly.

Local stations are picked up from Mount Wilson, about 15 miles away at 3200'-3600' elevation. Attempting to pickup stations from Mt. Wilson can be a good test for multi-path interference from this location. About 5 miles away is a large mountain peak that rises about 1000' above my line of sight with the transmitters. Signals must travel either over or around this peak. My receiver must differentiate between the good signals and the bad. The direction of my antenna indicates that strongest signals are traveling directly over the peak. The signal either bends over the mountain (knife edge effect) or reflects off the atmosphere to reach my antenna. For this condition, a medium gain antenna with good multi-path rejection (high F/B ratio) performs best.

Long distance stations are picked up from San Diego, about 130 miles away at a 700'-1800' elevation. There are no significant mountain peaks in my line of sight. Due to the distance, the line of sight is actually being blocked by the curvature of the earth. San Diego is a coastal town, most of the path the signal travels is along the coastline. Because of this, weather becomes a critical factor in signal reception. In favorable weather conditions, signal levels can be very high with the help of tropospheric ducting. In bad weather conditions, the moisture and fog in the air can create a wall of water. The lack of the ducting causes the signal to completely disappear. A high gain antenna is required to pick up these distant stations, but you will still need favorable weather conditions to get reliable reception.

Test equipment:

Set Top Box -Tuner Dish 6000
Horizontal rotator CM-9251
Vertical rotator ATF-V100
Pre-amplifier None
Spectrum Analyzer Tektronix 7L12
Coaxial cable RG-11, 50' antenna to receiver
Antenna Height above ground 30' = 17' house + 13' mast
Lower mast 1.375" diameter, telescopic 30-48", 3" increments
Upper mast (2) 1.250" diameter x 4-1/2' length, tempered steel, interlocking connection 
 

 


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