OZ1BXM Satellite station and antennas

Yaesu FT-847 transceiver
Yaesu FT-847 VHF/UHF transceiver.

Transceiver for 2m and 70 cm 
My 2m/70 cm transceiver is the Yaesu FT-847 satellite transceiver. It runs on 13.8V DC and delivers 50 W output on 144 MHz and 432 MHz.

Kenwood power supply PS-30
Kenwood PS-30 power supply.

Power supply
Kenwood PS-30 is a 13.8 V DC power supply delivering 15 A continuously and 20 A intermittent. It runs 100% noiseless - there is no fan inside!

70 cm preamp by HA8ET
70 cm preamplifier.
70 cm preamplifier updated
EXTRA-70 is mounted close to the antenna. It is manufactured by HA8ET and has adjustable gain. It employs a helical filter and works between 430-440 MHz with NF 0.5 dB (typ). IP3 is more than +27 dBm (good in contests). The preamp is powered from the transceiver via the antenna cable. If power is not supplied, the preamp input is disconnected from the antenna and grounded. This is a sound procedure for lightning protection.

23 cm transmit converter.
23 cm transmit converter.

23 cm transmit converter
My 23 cm transmitter is the MKU 13 OTX up-converter from Kuhne Electronic in Germany. The leftmost SMA-connector is the 144 MHz IF input. The SMA-connector to the right is the 1268 MHz RF output. The power level at 1268 MHz is about 1 W.

Physical dimensions are 55 mm x 75 mm x 35 mm (connectors not included).

The converter is connected to the IF radio using Aircell 7 double screened coax cable.

You can find the circuit diagram here .

13 cm receive converter
13 cm receive converter.

13 cm receive converter
My 13 cm receiver is the MKU 24 OSCAR down-converter from Kuhne Electronic. The leftmost N-connector is 13 cm input. The other N-connector is the 2 m IF output.

Physical dimensions are the same as the 23 cm transmitter described above.

The converter is connected to the IF radio using Aircell 7 fitted with N-connectors. Aircell 7 is a flexible, double screened coax cable.

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.



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 on Ebay (it was second hand). It was in good working order, but I had to replace the 500 ohm potentiometer inside the housing.

I've added a 5V DC PSU inside the control box. The rotator potentiometer is supplied this voltage. The voltage on the potentiometer's wiper is measured by the RCI-SE board. The wiper voltage is proportional to the position of the antenna. 0.07 V corresponds to 0 degrees, and 4.60 V corresponds to 360 degrees. 

The original Yaesu control box serves as a power supply for the rotator.   


  the antenna

  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 26-07-2016.