E.M.E.
Earth-Moon-Earth
"If your 2 meter station outputs 100 watts or more to a good 16 element Yagi antenna, and your receiver front end has reasonably low noise, you may be able to work BIG-GUNS MOONBOUNCER via 2 meter moonbounce. Point your antenna at the horizon as the moon nears set or shortly after it rises. Whenever eme conditions are favorable. Skymoon can help you determine the best operating dates & times."
 | What Kind Of
Station Is Needed To Work 2m EME? First, let’s look at the minimum station that could work some of the "big gun" or "larger" stations assuming that many of the variables discussed in the preceding section are favorable. We’re referring to CW EME where code speeds are usually in the 10 to 15 wpm range with some stations sending up to 20 wpm. Some of the bigger stations can, occasionally, complete contacts via SSB but FM is not used. Also, JT44, a digital mode of communications, will briefly be discussed later. For now, assume CW.
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| Digital
Techniques As part of his WSJT software program, Joe Taylor, K1JT, has recently developed JT44 for EME operation as an enhancement to WSJT. Many people have been experimenting with JT44 and are having tremendous success. Please visit K1JT’s website at http://pulsar.princeton.edu/~joe/K1JT for additional information. This digital mode of communications apparently has about a 10 dB snr advantage over CW and will make it much easier for a minimum sized EME station to work a greater number of other stations than would be possible on CW except for under the best of circumstances. At this time, I have not had any personal experience using JT44 but applaud Joe Taylor for his tremendous contribution to amateur radio. Since I get very excited hearing that CW signal being reflected off the moon, my personal emphasis, at this time, is on improving my station so I can work many new initial stations on CW. Good articles on JT44 appeared in the June 2002 issue of CQ, the Spring 2002 issue of CQ-VHF, and the June 2002 issue of QST.
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| Selecting The
Best Times To Operate And Setting Up Skeds When starting out on 2m EME, and especially if running a minimum sized station, try to concentrate on weekends that show conditions as "Good" or "Very Good" on W5LUU’s Weekend Moondata chart as long as it’s not within one or two days of a new moon due to sun noise.
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| Minimum
Station Antennas – A single yagi, horizontally polarized (not circular) with about 12.5 dBd gain (orabout 14.6 dBi gain) with an azimuth rotator should be sufficient. Having the ability to elevate the antenna will give a lot more flexibility as to when you can operate along with a lot of moontime. With no elevation, you will only have about one hour of moontime at rise and set along with the potential for ground gain enhancement. Depending on your QTH, however, terrestrial noise may be worse with the antenna on the horizon. Don’t expect to hear your own echoes with this minimum station. Receiver, Transmitter and Power – Any reasonably good 2m receiver and transmitter ortransceiver that can operate CW can be used. Either a receiver RIT (or clarifier) or split VFO will be needed to be able to compensate for doppler shift. A narrow IF filter (such as 500 Hz bandwidth) and/or internal or external DSP capability will help improve the signal-to-noise ratio of any weak EME signal being heard. A "brick" power amp with at least 150 watts output is the minimum power needed. Preamp and Feedline – A low noise preamp with a noise figure of less than 1.5 dB isneeded. At 2m, it can be mounted in the shack as long as good low loss feedline is used. The shorter the length of feedline, the better. With the preamp in the shack, low loss feedline will minimize the degradation of the receiver noise figure and maximize the amount of transmitted power getting to the antenna. Preferably, the feedline should be under 50 feet of Belden 9913, LMR 400 or comparable. For longer runs, consider using heliax. RG-58 should never be used and RG-8 probably shouldn’t be used due to losses. Ideally, the preamp will be mast mounted at the antenna. It needs to be protected from transmitting into it either via internal RF sensing and relays when lower power levels are being used or with a sequencer when running higher power levels.
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