"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.
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.
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
Antennas– A single yagi, horizontally polarized (not circular) with about 12.5 dBd gain (or
about 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 or
transceiver 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 is
needed. 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
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