EME station for 144 MHz
My EME Equipment
Station configurationMy station
configuration is show in figure 1. The 1 kW SSPA
is connected to the antenna array using 22 meters of Ecoflex
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.
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.
Fig. 1. Station configuration for 144 MHz EME.
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.
Fig. 2. My 4x6H antenna array for 144 MHz EME.
array for 144 MHz is 4x6H which is four stacked 6-element yagi-antennas PA144-6-2
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 1½" aluminium tubes.
The power splitter is fitted using a
homemade clamp. The two grey boxes contain Relay 2 (coax-relay) and the preamp.
Fig. 3. Antenna mast.
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
a steel wire, and a pulley.
The upper tube is 1½" steel and the length is
2.5 m. Two PLS50
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
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
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).
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
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
1½" steel tube.
I made my first EME QSOs with this array.
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)
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.
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
Note: The Graves radar has stopped operating on 143.050 MHz.
Distance to the MoonThe
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.
The Moon is 390.000 km away from Earth.
Latest update 16-July-2021 by Lars Petersen, OZ1BXM.