In early 2007, I decided to try 2m moonbounce using WSJT's JT65B digital mode. Over the years, moonbounce has gradually drifted away from CW to the much less demanding weak signal digital mode, allowing smaller stations to still explore the excitement of exchanging signals via reflection from the lunar surface. I am fortunate to have an excellent QTH for such an endeavour, being located beside the ocean with a saltwater horizon favoring moonrises, especially during the winter months of more northerly lunar declinations.
|Moonrise from front yard|
I soon realized that the actual numbers appeared very close to predicted values and using an inexpensive 2m FM/SSB 'brick amplifier' (with built-in GasFet preamp) delivering approximately 140 watts, I was able to work 54 different stations over the next twelve months. All of the stations worked were doing the heavy lifting, with the majority running typical 4-yagi H-frame arrays using yagis from 6 to 17 elements each. I did work one station that was using two small yagis during a period of excellent conditions. Somewhat surprisingly, a large majority of the stations I worked were strong enough to be heard audibly from the transceiver's speaker.
I'm always amazed at the truly small amount of RF energy that is actually left, after the round trip to the moon ... yet information can still be exchanged. On 144MHz, the round trip losses are a minimum of 250db. Factoring-in my antenna's gain and ignoring the coaxial losses in 70' of RG213, there is a scant 1.56 x10^-9 W arriving at the moon ... that's .00000000156 W! Considering how much RF is absorbed in the lunar dirt and what's left over for the -125db home trip, it's a miracle that some signals are loud enough to be heard by ear at all. EME is really one of ham radio's most fascinating activities.
Reacquainting myself with the newer version of the JT65B software, and testing out the system, I was ready to go on the next evening's moonrise. Unfortunately the moon was rising just a little too far south to give me a really clear shot and I would be pointing into the next door neighbour's trees. Being unable to track the elevation, my operating time is limited to about two hours per session, over a period of several successive days (or nights).
Almost coincidental with the night's moonrise, I heard the strong signals of RX1AS (Alex) in St. Petersburg, calling CQ. I called him and he came right back with my signal report. His station is shown below, along with his large homebuilt strip-line amplifier.
The following evening, the moon was buried even deeper into the trees but initials #56 and #57 were worked ... YL2GD (Gunars), in northern Latvia and RX3A (Nikolay), in Moscow city.
|YL2GD and his EME station|
|RX3A's 2m EME array|
Nikolay was worked with the moon at 11 degrees above the horizon. I'm not sure just what my upper limit for lunar elevation might be with this small antenna but the highest elevation I have worked anyone was at 18 degrees.
The third night found less activity on the band as well as a more southerly moonrise, burying my target even further into the neighbour's trees. Few signal were heard but one contact was easily completed with I3MEK (Mario), near Venice ... initial #58.
|I3MEK's 4-yagi 2m EME array|
|I3MEK's 2m JT65b signal|
With so many larger (four or more yagis) stations around the world, a huge antenna is not needed to have success on 2m JT65B moonbounce ... nor is an over-the-ocean moonrise. I've also been able to work stations on moonset where I am pointing over hilly terrain and trees, nowhere near the ocean.
The WSJT (JT65B mode) software is freely available and very easy to implement, but spend some time reading the manual and playing with the software first, perhaps getting used to QSO procedures on 20m.
If you are running a small FM/SSB amplifier on 2m, such as the typical 'brick' I have been using, make sure to add a blower to keep the heatsink cool, as JT65 has a 100% duty cycle and these small amplifiers can get hot pretty fast. I use a small squirrel-cage blower from an old microwave oven to direct a blast of air onto the cooling fins.
Wondering where to point your antenna? One handy site that will provide the moon's position in the sky, for any time and any location, is the U.S. Naval Observatory's 'Sun or Moon Altitude/Azimuth Table'. As well, you can keep abreast of real-time activity or set up skeds, via NØUR's Ping Jockey JT65 EME page.
If you do decide to give this a shot, I'd be interested to hear how you do ... maybe your system is big enough already to let us work each other via the moon.