EME station for 144 MHz

My EME Equipment

Yaesu FT-847sspa forfra
Antenna 4x6 yagi sequencer
Yaesu FT-8471 kW SSPAAntenna (4 x 6 H)Sequencer

Station configuration

My station configuration is show in figure 1. The 1 kW SSPA is connected to the antenna array using 22 meters of Ecoflex 15 low-loss coax cable (coax2). The loss in this piece is 0.76 dB which equals 160 W when running 1 kW. Remaining cables are standard low-loss coax cables.

The four 6-element yagi antennas are PA144-6-2 from the company Dual (YU1CF, antennas-amplifiers.com). Each antenna has 9 dBd gain, and the 4x6 array is about 15 dBd. The power-splitter is from the same company.

Relay1 is a 250 W coax-relay (Tohtsu CX-140) in my shack. Relay2 is a 1 kW coax-relay (Tohtsu CX-600) sitting in a box near the antenna. The bias-T is from Wimo.de, and the sequencer is homemade. The preamp is Extra-2 from HA8ET with typ. 0.5 dB NF. It receives when 12 V DC is applied via the bias-T. During transmit periods, power is removed from the preamp, and a relay connects the input port to ground. The preamp is housed in a water-proof box mounted near the antenna.

144 MHz EME lay-out cables
Fig. 1. Station configuration for 144 MHz EME.

The power splitter, Relay 2, and the preamp are sitting in the mast near the antenna. Relay 2 and the preamp are inside a grey plastic-box. The SSPA is in the shack together with relay 1, the bias-T, the sequencer and the 2m transceiver. My Windows computer is not shown in figure 1.

Antenna array

144 MHz EME Antenna year 2020 OZ1BXM
Fig. 2. My 4x6H antenna array for 144 MHz EME.

My antenna array for 144 MHz is 4x6H which is four stacked 6-element yagi-antennas PA144-6-2 with horizontal polarization. The stacking distance is 1.90 m horizontal and 1.90 m vertical. These distances are shorter than the factory recommended which are 2.40 m horizontal and 2.20 m vertical. All four antennas are mounted on an H-frame made of 1" aluminium tubes. The power splitter is fitted using a homemade clamp. The two grey boxes contain Relay 2 (coax-relay) and the preamp.

Antenna mast

Antenna mast 2020
Fig. 3. Antenna mast.

The lower tube is 2" steel, and it is attached to the house wall using 2 common antenna brackets. Tube length is 4 meters. This tube can be "laid down" on the lawn using the winch on the brick wall, a steel wire, and a pulley.

The upper tube is 1" steel and the length is 2.5 m. Two PLS50 platforms from UKW-Berichte are attached to the lower tube and holds the upper tube. The lower platform supports a Yaesu G-600 rotor, and the upper platform supports a thrust bearing KS065.

Rotor system

You can view my rotor system in fig. 4. The antenna is turned horizontally with a Yaesu G-600 rotor (6a), and elevated with a Kenpro KR-550 (6b). Both rotors are controlled by the ERC-3D rotor controller (4) which interface the 2 control boxes (5a and 5b) using several relays. The relays are inside the ERC-3D box. The controlling software is PSTRotator (2). PSTRotator has a separate window dedicated to Moon tracking (1). The interface between the PC and the Rotor Controller is a USB-to-serial converter (3).

2 rotators
Fig. 4. How the rotors are controlled by PSTRotator.

PSTRotator (2) runs on my Windows 10 computer. PSTRotator receives Az/El data from WSJT (not in the figure). The main window (2) shows the position of the two rotators. The green arrow points at the current rotator position, and the black arrow points at the "go to" position. There is a dedicated window for EME (1) in PSTRotator. The rotor controller (4) is under the control of PSTRotator via a serial USB-interface (3). The rotor controller (4) contains 4 relays, which are used for "pressing buttons" inside the two control boxes (5a and 5b). The buttons UP, DOWN, RIGHT, and LEFT are controlled by the ERC-3D rotor controller (4). The rotor controller receives position data from the rotors (a voltage between 0 and 5 V DC). The rotor controller will "release the button" when the rotor (6a or 6b) has turned the antenna to the proper position.

Earlier EME antennas

4 x 6 yagi 144 MHz EME antennaAutumn 2017
My antenna array was 4x6H which is 4 stacked 6-element yagi-antennas PA144-6-2 with horizontal polarization. The stacking distance was 2.40 m horizontal and 2.20 m vertical. All four antennas were mounted on an H-frame made of 1" steel tube.

I made my first EME QSOs with this array.

The array was mounted on top of a 6 meter long 2" steel tube. However, the tube was bent during a heavy storm in the autumn. Because of this, I decided to redesign the EME-antenna:
  • shorter antenna mast
  • lighter materials in the H-frame (alu-tubes)
8 element yagi for 144 MHzSummer 2017
I employed an 8 element horizontal yagi (11 dBd gain) with two rotors (Az/El). My sked with HB9Q (monster station) was not successful. I tried with another big station. He used horizontal polarization first, and then vertical polarization; no signal was heard. 
2 x 6 yagi 144 MHzSpring 2017
I used a 2 meter long ash tree cross-boom with 2 x 6 element yagis. This array was light and the wind resistance was low. The two 6-element yagis were PA144-6-2 from the company Dual (YU1CF). Each antenna had 9.2 dBd gain and a pair provided 12 dBd gain with vertical polarization. I heard the Graves radar (143.050 MHz) and a few powerful EME stations using these yagis. No QSO. I decided changing from vertical to horizontal polarization in order to hear and work EME-stations.

Note: The Graves radar has stopped operating on 143.050 MHz. 

Distance to the Moon

The distance from the Earth to the Moon is not constant; it varies between 362.600 km to 405.400 km. The photo below was taken from the OSIRIS-REX satellite, about 3 million miles away, dated Oct 2, 2017. The Earth-to-Moon distance on this day was 390.000 km (242,000 miles). The photo was posted by Mike Cooper in the Facebook group Earth Moon Earth (EME) Radio Communications.

Earth and Moon on same picture
The Moon is 390.000 km away from Earth.


Latest update 16-July-2021 by Lars Petersen, OZ1BXM.