Hams in Space!

I
in a favorable sky position, Activity peak s
when the moon is within common view of
both Europe and North America. Random
activity can be found from 144,(0) MHz to
144 .020 MHz . Schedules are ru n bet .....een
144.020 MH z and 144. 100 MH z. Singfc
sideband voice is so meti mes heard o n
144 .105 MHz. I usuall y operate CW on
144 .008 MHz during such times, and abo on
wcckdays a fter work. Many CQs are ca lled
by myself, W5UN, and others du ring these
times.
Schedule :\I akin~
EME operation is either random (calling
and answering CQs), or scheduled. Let 's discuss
schedule operating procedures first.
Schedules are made in several ways. The
best way is to check into the 2 meter EM E
net beginning around 1730 UTC every Sat ­
urday and Sunday on 14.345 MHz. Direct
telephone ca lls to the statio n you want to
make a schedule with is another way , I've
set up many schedules .....ith small stations
this way. A third way is to request a schedule
by mail.
Schedules usually last for one hour, but
may be longer or shorter as agreed to by the
participants. Smaller sta tions usually run
schedules for one hou r . Du ring schedule
making, a frequency and time arc agreed on,
und the two ru nning stat ions are designated as
being either cast or w est. depending on their
relative locat ion to one another. When a
schedule begins, the eastern station transmits
for the first two minu tes beginning at the top
of the hour. If the schedule starts at a time
other than the top of the hour, the same twominute
periods are used as ifthe schedule had
sta rted on the hour. If you are ru nning a
schedule with a station to the east ofyou, that
station would be the eastern statio n, and you
would be the weste rn station. The two-minute
transm it/rece ive sequencing will co ntinue
until the schedule is completed or until time
runs out.
For successful 2 meter EME QSOs. you're
required to exchange call signs, O's, RO ' s,
and R's. This data must be received and acknowledged
by both stations. 73s are usually
sent also, but th is is optional infonnat ion.
Let's consider a schedule example.
The table illustrates ho w a schedule between
W4ZD in Florida and ZD8MB on Asce
nsion b land might progress, and sho ws
how the informatio n discussed above is hand
led. Let's say they have a one-hour schedule
starting at 1(0) G MT. ZD8M B is east o f
W4ZD. so he is designated as the eastern
station, and will transmit the first two min­
will send calls over and over
utes. ZD8 ~1B
for the full two minutes (W4ZD de ZD8MB).
W4ZD begins sendi ng at 1002 GMT. If
W4ZD heard the calls, he will send ZD8MB
de W4ZD for the first minute and a half, and
O's for Ihe last half a minute. If W4ZD
doesn't hear both calls, he calls only for the
full two m inutes. This co ntinues until eithe r
station has heard both calls and O. Once an 0
is heard, the station hearing it responds with
RO's during his next transmission for the full
two minutes. The station copying RO 's has
52 73 Amaleur Radio Today. March,1991
received sufficient infonnation for his part of
the QSO . When the station transmitting RO's
hears an R, that station has received sufficient
information for his part, and the QSO is essentially
complete. Most stations, upo n hearing
R's. will respond with R's and 73s to let
the other station know that R's have been
received.
RandomQSOs
Having read all that about two- minute sequences,
you will find thai a lot of random
activity is conducted with one-minute sequences.
In fact , nearly all my random QSOs
are of the latter type . If stations are hearing
each other well enough to copy random calls
in one minute , add itional time is not necessary,
Random activity is quite a challenge for the
less equipped, smalle r station. However, by
an swering the CQs of larger stations transmitting
on the bottom 20 kHz of2 meters, it is
possible to make QSOs, It is well-known that
the signal level of a scheduled station ean be
several dB less than that ofthe weakest identifiable
random calling station. A listening operator
can mentally fill in the missing parts of
a very weak station's call when he already
knows what the call will be. Also, when the
ope ra to r knows a certai n station will be
calling on schedule, he shifts his ears (and
brain) into a more focused , selective mode in
order to dig thai station out of the noise . For
these reasons, small stations are urged to
make advanced schedules whenever possible.
However, don't give up on answering
random CQs, because you never know ifsuccess
is possible until you try ,
I must tell you one more thi ng about schedules
and the pre- knowledge of callsign information:
It takes discipline to assure yourself
that you 're hearing what you th ink you're
hearing when you dig deep into the noise for
long periods. Some operators ca n manage
this sel f-d iscipline better tha n others. Remember,
you will only shortchange yourself
and the station you are scheduling if you
acknowledge QSO information that you have
not truly heard, but only thought you heard
or, worse, have guessed at. This is another
reason why I enjoy random operation: I don't
have to be as disciplined about what I thought
I heard, since I actually must hear the full call
to know who is calling.
The Effects of Conditions
A sig nal of constant strength transmitted
from Earth and then reflected back never
yields the same signal level in a receiver from
one moment to the next. There are many
factors which cause this phenomenon. Some
of these factors are well understood and predictable
. Some are only pa rtially understood
and are not so predictable , There are probebly
a few factors that haven 't even been
thought of yet. Some of the sig nal variations
are short-te rm (such as those caused by
moon/Earth libation), and some are longterm.
such as those caused by Eanhfmoon
distance separation. Libation effects are very
short-term (milliseconds) and are of little interest
to EME operators. Longer-term factors
are of great interest because EME
scheduling and operation times are chosen
based on a set of such predictable factors. I
will explain these factors shortly, There are
also some factors which ca nnot be predicted
in advance, but which ca n greatly affect EM E
communications, I will briefly discuss these
also.
The distance of the moon fro m Earth, the
position of the moon in the sky (that is, the
background sky when looking at the moon),
and the phase of the moon during its 29-day
cycle all have well-known effects on reflected
echo strength, relative to system noise. Du r­
ing the 29-day cycle the moon ranges from
apogee (furthest from Earth) to perigee
(nearest to Earth). At apogee, the strength of
a returning ec ho will be about 2 dB less than it
will be at perigee, all other thi ngs being eq ual
(which they seldom are). Also, during the
29-day cycle ofthe moon the background sky
noise levels at 2 meters will vary fro m 175
degrees to over 5000 degrees Kelvin. (The
higher noise occurs when the moon is positioned
against the galactic plane, which happens
near the moon's most southerly dectination.)
This noise equates to dB readings from
1.75 dB to over 10 dB . Sky noise and path
loss are the key data elements used by EME
operators to determine the best operating
times du ring the moon cycle.
Factors affecting the moon which are not so
easily predictable are the effects caused by
the Ea rth's geomagnetic field as the signals
pass through it on the way to and from the
moon. One such effect is Faraday rotation.
This causes the polarity of signals to rotate
from horizontal to vertical and back. Faraday
rotation can cause a signal to null-out (or
peak) depending upon what type of polarity
your antenna has. Polarity see ms to rotate
quite natu rally at about 1.5 minute intervals
when the geomagnetic field is normal. However,
things are seldom "normal" with the
geomagnctic field (despite what WWV says),
and sometimes rotation loc ks up for long periods
of time. Another situation caused by
geomagnetic activities is where signals .seem
to be dispersed or absorbed, rather than rotated.
At such times, it doesn't seem to make
any difference what your antenna polarity is.
Even if you could rotate polarity (as some
stations can) it wouldn't help. I have also
heard sig nals greatly enhanced in stre ngth
when the geomagnetic lield was disturbed,
although many times when this happens,
communications is one-way, and stations at
more northern latitudes will hear nothing for
long periods of time. Then the situation reverses,
and the southern stations are locked
out, So, it is difficult to determine in advance
just what the effects will be for a given time
and.condition. There is still a lot to be understood
about suc h effects on EME communications
before predicting methods ca n take
them into account.
There are are a few other rules of thumb
about EME operating conditions. Overall,
nighttime seems to be better than daytime for
EME operation (perhaps because ionization
and consequent absorption is less of a proolem).
Butl have heard some very good cordi-