N2UO Parabolic Dish Antenna

N2UO EME and Satellite parabolic dish

I built this antenna from scratch in the basement using only common hand tools and a borrowed welder.

The design is the classic stressed type, but the spokes have been pre-bent to improve the shape. In this way I achieved an f/d of 0.45, not common with stressed dishes. This brought the feed closer to the reflector, making the structure smaller. The antenna performs very well and its gain is 30 dBi at 1296 MHz. A standard ham azimuth rotator is used, but I feed the AC through a diode so only half the cycle is applied. This results in very slow rotation speed but still high torque.

When not in use, the antenna is kept between the house and some trees. I can move it around the yard because it is mounted on casters. Three small concrete blocks with a buried nut and a pipe serve as a leveled surface and maintain the calibration of the azimuth positioning.

The antenna movements are controlled by an auto tracker. The moon, the sun and other celestial bodies can be automatically tracked. The tracker is based on an OE5JFL design.

The 23 cm EME feed is a scalar ring type, and a 4 turn helix is used to receive AO40 on 2.4 GHz, and another concentric 2.25 turn helix is used for the L band uplink. I under-illuminate the dish on S band on purpose to achieve the same beamwidth of the uplink frequency (about 5 degrees).

 

Azimuth rotator

Elevation

 

 

Casters

 

 

Feed

 

 

Controlling surface accuracy with template

 

 

Winter time operation

 

 

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