Achieving contacts by moon bounce has been a ham radio goal of mine since I was first licensed. Part of the allure is the exotic concept of communicating with another station half way around the world by bouncing your signal off the moon. The other part is the technical challenge involved.
The difficulty of moon bounce is the due to the path loss, about 250 dB on 2 Meters (144 MHz). Think about it – going from .1 μW to 1 KW is only 100 dB. Historically it required full legal limit power and monster antenna systems. EME (Earth-Moon-Earth) contacts were made with slow speed CW (Morse code).
The bar was lowered when Joe Taylor, K1JT, introduced the WSJT suite of software programs for VHF work. The JT65 mode’s modulation is optimized for the propagation mode. DSP algorithms using the PC sound card dig deep into the noise to extract the signals. More modest stations are now capable of making EME contacts.
I made my first EME contacts a few years ago with a single Yagi and 120 watts. Contacts were at moon rise (which can give several extra dB from the signal reflected off the ground) and were with monster stations like W5UN. I wanted to be able to contact more stations which would require a bigger antenna and more power.
The project is being done in phases.
Phase 1. Install tower with two 13 element Yagis with azimuth and elevation control. This was completed at the end of December, 2009.
Phase 2. Increase power from current 160W amplifier. I have an RF deck obtained in a swap that uses a pair of 4CX250s. I need to build a power supply for this.
Phase 3. Build a larger antenna system consisting of 4 home brew Yagis.
So far I am happy with the results at Phase 1. I have been able to work stations with arrays of 4 Yagis with 12 or more elements running a KW or so when conditions are right. Ultimately my goal is to work 100 DXCC countries and finish my 2M WAS which currently stands at about 35 states worked by terrestrial propagation modes.
Current EME Station
Transceiver: Yaesu FT-847
Amp: Mirage B2518G (160W)
PC I/F: Unified Microsystem SCI-6
Antenna: 2 Cushcraft 13B2
PowerPoint and streamed video links to my talk "EME for QRPers" can be found here.