144 MHz EME

EME Equipment

Yaesu FT-847sspa forfra
Pre-amp by Microwave Modules
6EL2 Vargarda antenna
 sequencer
Yaesu FT-8471 kW SSPAHA8ET PreAmp 2 x 6 element yagi (2.25 m boom)Sequencer

The equipment above is sufficient for a beginner's EME station. The weak link is the antenna. DK3QN Klaus recommends EME antenna gain be 15 dBd (see his excellent EME page)

EME Station Configuration

My EME station is pictured below (fig. 1). The power splitter, the preamp, and Relay 2 are mounted on the mast as close as possible to the antenna. The SSPA, the PSU, the sequencer, and Relay 1 are sitting on an equipment shelf about 6 meters from the antenna.

Placing equipment close to the antenna provides several benefits:
  1. The low NF of the preamp improves reception 
  2. The preamp gain compensates cable loss
  3. Power loss between SSPA and antenna is minimized
If the SSPA was in the shack and fed with 25 meters of RG213, I would loose about 250 W in the cable at 1 kW output. The station layout below requires only a short length of low-loss coax between the SSPA and Relay 2 (about 80 W is lost). Remaining coax is standard cables. This station configuration requires only 1 high-power coax relay (Relay 2). 

EME station config.
Fig. 1. EME Station Configuration.

#1 draft on EME antennas  

I've planned a 2 x 8 element yagi array with elevation. The antennas will be vertically polarized. Each 8-element antenna has 11 dBd gain and the boom length is 3.8 m. A pair of these antennas would provide 14 dBd gain. I would be able to benefit from long operating hours since the array will point at the Moon as long as it is visible. Elevation also reduces terrestial noise, which is strongest when the antennas are pointing at the horizon. 

#2 draft on EME antennas

December 2016. I have reviewed the antenna design. The previous draft had 2 x 8 element yagi. It required a 3 meter long center boom made of steel tube. This kind of boom would be too heavy for my KR-550 rotor. I am not sure the rotor can handle this weight.

My new solution is using a 2 meter long wooden center boom (ash tree), and fit 2 x 6 element yagis. This array will have less weight, and the wind resistance will be lower. It will be easier for the KR-550 to elevate it. The two yagis will be 6EL2 from the swedish company Vargarda. Each antenna has 10 dBd gain, and a pair will provide about 13 dBd gain. The antenna's boom length is 2.25 m.  

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Page updated 02-Jan-2017 by Lars Petersen, OZ1BXM.