144MHz EME Antenna Array

Some photos of my 144MHz EME Moonbounce Anntenna build


144MHz Earth-Moon-Earth, again

After packing up and moving interstate, I have finally got around to re-erecting my old 144MHz moonbouncing station. This time around I have a much bigger backyard and am in a quieter (radio noise wise) environment.
I can hear and decode signals that were not even visible in my former location. This is where the LFA design really shines. The Gain to Noise Temperature (G/T) ratio of this design makes an appreciable difference to my detection capability.

NEC Listing

For anyone interested in modelling the antenna that I built, here's the NEC listing. Bear in mind that I used the NEC4 engine for the simulations.



lfa.nec

Feedpoint Considerations

My approach to feeding the LFA antenna is a simple one: use a decoupling choke on the coax, and leave the folded dipole free to find it's own balance point - don't force the opposite end to ground. Instead, use a quarter-wave section of coax, connected to the feed at one end, shorted to the boom at the other to maintain a DC short and noise immunity. The choke offers close to 500 ohms of impedance at 144MHz, so 2 chokes per yagi is more than good enough to choke off any current on the outer of the coax.

Simulation Results

The following results are from a NEC4 simulation. I have understacked the antennas to improve sidelobe levels, at the expense of around 0.8dB of forward gain.


NEC4 Elevation Pattern

Free-space modelling of the Elevation Pattern of the array.

NEC4 Azimuth Pattern

Free-space modelling of the Azimuth Pattern of the array.

Return Loss measurements

Return loss of each Antenna. Still not sure why #2 is a bit different.

Tower Hardware

The tower is mounted onto a plinth with a hinge and brake winch, which makes antenna maintenance a simple task

Tilt-over Tower

The tower foundation and plinth.


Tracking

Testing the tracking system.

In Operation

Tracking the moon.


Preliminary Results

I am still testing the system but preliminary results indicate that this system is working well, albeit with a bias towards a better receive than transmit capability. That said, I am happy to see that in the space of around 1 month, I have managed 4 QSOs with single yagi stations.

Useful Links


News

Moon Tracker ver 3
22/03/19 A new version.
144MHz EME Array
20/02/19 Resurrect the old 144MHz high gain antenna array.
Thunderbolt
06/11/17 Make allowances for the Thunderbolt date rollover issue.
1296MHz Activities
26/06/16 Antenna Improvements.
Moon Tracker ver 2
23/06/16 A new version.
1296MHz Activities
29/09/15 Build a small dish.
LNA
26/07/15 Low-noise Preamplifier Design.
1296MHz Activities
19/04/15 Power Amplifier Design.
1296MHz Activities
13/01/15 Design and build a tower for 3m parabolic dish.
Thunderbolt
30/09/14 LCD monitor for my Thunderbolt GPSDO.
PANFI
02/08/14 A home-made Noise Figure Meter.
Moon Tracker Update
09/04/14 New rotator and better position feedback sensors added.
1296MHz Antenna
09/02/14 Begin construction of a 1296MHz feed horn for the 3m dish.
1296MHz Activities
28/01/14 After success at 144MHz, operation at 1296MHz is planned.
Moon Tracker Update
11/09/13 Added a Background Sky Temperature calculation into the Moon Tracker.
Moon Tracker Update
28/08/13 Just Added some software limits to rotation of motors.
Roger Beep installed
09/08/13 Added a Roger Beep to my radio.
Andy's Website
06/05/13 Start build of website.

Contact

Andy, VK3ANX
Yarra Valley, Australia
Andy