Hams in Space!

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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 twominute 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-
• tions during daylight, so don 't give too much weight to this. Winter, on the average, seems to have better EME cond itions than summer, probably for similar reasons. The new moon can affect EME communications. Noise from the sun will mask weak signals during new moon. The moon is not usable for EME work for about two days centered around the new moon date. There will be many days during the cycle when the moon cannot be seen because it is up during daylight. EMEcomm unication is quite possible most of these days , if you can aim your antenna without seei ng the moon. Computer Programs A number ofprog rams that compute moontracking data , essential to sched uling and antenna-a iming , run on ham shack computers. The best ofthe more modem programs run on IBM personal computers, Other computer software for Commodore computers , HP cal cularors, and others, can still be obtained, or even easily written. Good moon tracking programs, such as W5UN 's SKYMOON, VK3UM 's REAL TRACK, and WAIJXN' s TRACKER, will give excellent directional antenna-aiming and a lot o f other pertinent EME data. lEd. Note: see the review of SKYMOON in this i.~ .~ueJ Many EM E operators use such programs to find the moon's azimuth and elevation (Azl Ell from any given point on Earth at any given time, so that they can arrange mutual schedules. In addition to moon position , these programs g ive moon apogee and perigee information, and moon bac kground sky noise estimates for each Az/El time interval calculation. Some programs go beyond this and also compute many other variables ofinterest to EME operators. EME Directory " The EME Directory," available from Bev Cavender W4ZD, P.O. Boll. 88 , Lake Placid FL 33852 is a good resource to have if you wish to know who the worldwide. active EME stations are , and what kind of station equipment they are using . The directory is also pan of rev ision 2 of the SKYMOON program. 2 Meier EME Newsletter " The 2 Meter EME Newsletter," published by John Carter K01FL, P.O. Box 554, Union MO 630lW about 10 times per year, helps keep EME operators infonned about who is active on EME, and who is working whom. 2 Meier E:\.IE Sel As I mentioned previously. the 2 meter EME net meets every Saturday and Sunday around 1730 UTC (after thc 70cm net finishes) on 14 .345 MH z SSB. Thi s is the " watering hole" where EMEers gather to e xchange information and make schedules. Newcomers are welcome to check in. VE7BQH is net control. III Dare Blaschke W5UN can be reachedat 9/01 Kings Drive , Manvel TX 77578. Try IRe's new HF trensceiver /S1-135 dt Ciffer's store. • Gen. cove rage triple conversion receiver, 100 kHz-30MHz. microprocessor controlled. direct digital synth. IC • lowdistortion adjustable power amp. 1O-15Ow out - Pass-band shift, Notch, Blanker, Processoc Dual VFOs, 200 ch memory, VOX, AGC, RIT, Squelch, FulVSemi Break-in. VISIT ClIFfI'S STOltE " 'tt::~'''''''~~i~ E~ y 10 f,,>le"f .... A f AX re"epl'on 'l~" "' Bile fully c"",,!>Ie ,~" e "" C"~n I>
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