Appendix; Eme (Earth-Moon-Earth) Operation - Yaesu FT-847 Operating Manual

Appendix

Perhaps the ultimate challenge in amateur radio is com-
munication achieved by bouncing signals off our
planet's moon. Moonbounce or "EME" communica-
tion was, for many years, an activity pursued only by
a few dedicated engineers. Today, however, the very
large antenna arrays used by some EME specialists
throughout the world have made it possible for ama-
teur operators with very modest antennas one or two
Yagis on 144 MHz, two or four Yagis on 432 MHz
to complete EME contacts while running small "brick"
solid state amplifiers in the 100W ~ 300W range. More
power and (especially) more antennas will improve
your results, of course, but two 13~17 element 144
MHz Yagis and 150 Watts will provide enough system
performance to allow you to work the biggest stations
via the moon under favorable conditions.
EME operation shares certain characteristics of both
terrestrial weak signal work and satellite work (the
moon is, of course, a "passive" satellite of earth).
These characteristics are:
¦ As with long-distance tropospheric DX, signals will
be weak, so it may be advantageous to utilize a mast-
mounted preamplifier, so as to optimize system
Noise Figure (by placing the low-noise preampli-
fier gain ahead of the losses in your coaxial cable).
¦ As with "active satellite" work, the operator must
account for Doppler shift of the operating fre-
quency.
¦ The position of the moon is constantly (though
slowly) changing, so the ability to rotate your an-
tennas in azimuth and elevate them above the hori-
zon is important. Above about 15º elevation, ter-
restrial noise (especially on 144 MHz) is signifi-
cantly reduced, making it easier to hear weak EME
signals. See your Yaesu Dealer for details regard-
ing Yaesu's G-5500 Azimuth-Elevation Rotator.
EME activity tends to concentrate on weekends near
moon perigee (the point of closest approach of the
moon to earth, usually around "full moon"). Details
regarding EME operation can be found in monthly
amateur magazines, as well as in books on VHF com-
munication which are available from your dealer. There
are also many sources of EME information and ad-
vice available via The Internet.
100
EME ( E
-M
ARTH
) O
-E
OON ARTH PERATION
O T
PERATING
The operational steps for your first EME contacts us-
ing the FT-847 are shown below.
•
Connect the FT-847 to your antennas and ampli-
fier/preamp as shown on page 15. As a general rule,
for 2 meter EME one needs (as a minimum sys-
tem) a pair of Yagi antennas at least 5 meters (16.4')
long (two side-by-side vertically polarized Yagis
otherwise used for FM work may be satisfactory)
and at least 150 watts of power.
‚
Set the FT-847 to the CW mode, and activate the
DSP Bandpass Filter (and NR filter, if you like).
Set the DSP Bandpass Filter to its minimum band-
width setting (25 Hz). If the optional YF-115C is
installed in your transceiver, press the [NAR] switch
to activate the narrow IF filter.
ƒ
Set Menu #02 ("MIN FREQ") to the 0.1 Hz selec-
tion. This will provide very fine tuning steps, which
are helpful when using the ultra-narrow DSP band-
width of 25 Hz.
„
Press the [CLAR] switch to activate the C
feature, so as to compensate for Doppler shift. If
you have software which provides Doppler shift
prediction, use the software to determine the cur-
rent Doppler shift expected. If you do not have such
software, the following guidelines (for a mid-lati-
tude station operating on 2 meters) will get you
started:
l As the moon rises in the eastern sky, signals will
be heard higher in frequency compared to the
original transmit frequency. As the moon re-
cedes toward the west, signals appear lower in
frequency compared to the original transmit fre-
quency.
l At moonrise in the east, 144 MHz Doppler will
be on the order of +500 Hz; your CLAR con-
trol should therefore be set to +500 Hz offset,
so that your transmit frequency is 500 Hz be-
low your listening frequency.
l As the moon reaches its highest point in the sky,
the Doppler shift will be reduced to zero (as the
moon is no longer "approaching" your location).
Therefore, as the rising moon reaches 45 de-
grees elevation, the Doppler shift may only be
about +250 Hz; adjust the CLAR control ap-
propriately.
FT-847 O
UTORIAL
M
PERATING
LARIFIER
ANUAL