Satellite antennas and rotator

2 m and 70 cm antennas

Yagis for 2m and 70 cm.

2 m antenna 
My 2 m antenna is a 3 element yagi (Vargarda Radio 3EL2). The boom is only 0.8 m long and the yagi is mounted in front of the antenna pipe (foremast mounting). Claimed gain is 7 dB relative to a dipole.

70 cm antenna
My 70 cm antenna (Vargarda Radio 6EL70) is similar to the 2 m antenna, except that it has 6 elements and the claimed gain is 10 dB relative to a dipole. 
 

23 cm antenna


20-turn helix antenna for 23 cm.

23 cm helix
My 20 turn RHCP helix antenna was acquired from Germany (Helix-23-2 from
Wimo). The antenna is temporarily mounted at ground level for testing. 

13 cm antennas

 
21-turns helix antenna for 13 cm.

 

13 cm helix - 21turns

This 13 cm antenna is a 21-turns helix from Wimo (Helix13). The helix is made of aluminium wire, which does not corrode like copper does. The polarization is RHCP. The antenna is temporarily mounted at ground level for testing.

5-turns helix antenna for 13 cm. 

13 cm helix - 5 turns 
My homemade 5-turns RHCP helix antenna is seen in the photo. The antenna is mounted on a tripod for testing purposes. 

 

 

Antenna rotator system

Rotator Control box
The control box.

 

Control box
This box contains the RCI-SE board and a power supply. The RCI-SE board is the heart of the antenna rotator system as it monitors the position of both rotators and adjusts them as the satellite moves acrosss the sky.

There are two meter circuits inside the box, one for azimut metering and one for elevation metering. Each meter circuit measures the wiper voltage of the rotator potentiometer and displays the value on an analog panel meter. 

Power is supplied from an external transformer. A PSU-board inside the control box feeds the RCI-SE board and delivers a DC voltage to the two rotator potentiometers. 

The EA4TX control software, which runs on my PC, supports a preset function. The user sets the desired compass direction. The rotator then starts, turns the antenna to the same direction, and switches off automatically.

RCI-SE









  board.

The RCI-SE board.

 

RCI-SE board
The Rotator Controller Interface - Special Edition board (RCI-SE board) is made by EA4TX and comes as a preassembled unit. It measures 12 cm x 12 cm and it is able to control two antenna rotators. 

The RCI-SE board is connected to the printer port (LPT-port) of my PC in order to communicate with the EA4TX control software.

The RCI-SE measures the actual antenna direction using A/D converters. Each A/D converter measures the voltage on the wiper of the rotator potentiometer. This value is converted into an 8 bit binary digit and sent to the control software on the PC.

The board controls the rotators by means of relays. In my case I'm using four relays: LEFT, RIGHT, DWN, and UP. The fifth relay (AUX) is intended for rotator brake control.

The RCI-SE requires 12 V DC at max. 150 mA, which is supplied from a homemade power supply board.

Yaesu G-600 rotator.
Yaesu G-600 rotator.

 

Azimuth rotator
The Yaesu G-600 rotator is used as azimuth (horizontal) rotator.

I bought the rotator used on Ebay. It was in good working order, but I had to replace the 500 ohm potentiometer inside the housing.

The potentiometer is supplied with 5 volts control voltage from the control box. The feed-back voltage, which is measured by the RCI-SE board, is proportional to the horizontal position of the antenna.

The original Yaesu control box is now used as a power supply for the rotator.   

 

Testing
  the antenna





  assembly
  on  the ground.
 Testing the antenna assembly on the ground.

 

Antenna assembly 

A 1" steel pipe (38 mm) is the moving part of the antenna assembly. This pipe is rotated by the G-600 and supported by the bearing KS-65 (just visible near the lawn).

 

Two stainless steel platforms (PLS 50 from UKW Berichte ) carry the rotator and the bearing. The platforms also create some distance to the permanent 2" (50 mm) pipe, which will be mounted on the brick wall of the house using wall brackets.

Antenna assembly mounted on the brick wall.

Antenna assembly mounted on the brick wall. 

Completed antenna project

This picture shows the completed antenna project.

The permanent pipe is mounted on the brick wall using ordinary wall brackets (they can be obtained in radio/TV shops).

The rotating pipe carries 3 antennas:

  • Upper antenna is a 6-element yagi for 70 cm
  • Center antenna is a 21-turns helix antenna for 13 cm
  • Lower antenna is a 3-element yagi for 2 meters


Written by OZ1BXM Lars Petersen. Latest revision 28-August-2009.

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