The amount of activity on 144 MHz has increased significantly since I first became active in the mid 1970's.  One of the reasons for this is that it simply is not that difficult, once you know how.  Even single yagi stations with good horizons are making dozens of contacts!  Getting on EME actually can be quite simple if you are planning a portable or small EME station.  If you are interested in giving EME a try on 6m, please read this page for a general understanding of EME, and then also go to the following page for special considerations involved with EME on the "Magic Band".

Of course, it always helps if at least a few things are done right in setting up a new EME station.  Many folks have broken trail before you, and there is no point in "rediscovering" the pitfalls yourself (unless you are a glutton for punishment and have endless amounts of time and money).  I first presented these general tips in the initial 144MHz EME DIRECTORY (printed by EIMAC in 1984).  These were based on personal experience as well as the experiences of others; the basic tenants are as true today as they were then.  I have enjoyed successful 2m EME operations from Vermont, Montana, Little Cayman Island (twice) and Abaco Island in the Bahamas (four times).  Following these simple guidelines will greatly increase your chances for successful operation, too.

Much frustration and disappointment can be avoided by getting off to the proper start; it is much easier to do it right the first time, instead of learning everything by your own misfortunes!  Even if you can do just a few things to optimize your chances, the following tips will help make your entry into 2 meter moonbounce much more successful and enjoyable.

1. PREAMPLIFIER -Use a good preamplifier for receiving and mount it right at the antenna.  I mount my preamp, along with the switching relays, directly on the main power divider at the antenna, and run flexible RG-58/U coaxial cable around the rotator, where it changes to RG-8/U coax for the run into the shack.  With the low prices of good transistors (GaAs FET's capable of noise figures under .5 db are readily available nowadays), there is no reason for not using a good one.

To protect the preamplifier from switching transients that can be coupled over to the DC power line for the preamplifier, I have had excellent success by running the 12 VDC up through the center conductor of the receiving coax, using a "bias tee".  Of course, with a commercially built preamplifier, you will have to follow the manufacturer's recommendations for providing power.  HOWEVER, the single largest problem with people blowing up tower mounted preamplifiers has been exposing the preamplifier power leads to switching transients in the wires going up to the coaxial relays.  These transients can be coupled over from wires several feet away, causing voltage spikes in the preamp power supply line, which also are running up the tower in reasonably (or very) close proximity to the other wires.  If you cannot run the power up to your preamp in a shielded cable, be sure to install an RF Choke and bypass capacitors immediately before it goes into the preamp.

The coax from the preamp to the receiver need not be anything special (most GaAs FET's have plenty of extra gain to overcome the line loss on the output of the preamp).  On DXpeditions, for example, I have always had good success with RG-58/U coax from the preamp down to the converter.  Just be sure that you have enough gain to overcome the noise figure of your receiver; you should see the S meter deflect slightly upward when the preamp is turned on.  However, if the meter deflects more than one or two S units, you are over-driving the receiver and should add attenuation ahead of it to assure maximum sensitivity.

2. TRANSMISSION LINE - You MUST get as much power to the antenna as possible.  In addition to using a good power amplifier, this means good quality low-loss transmission line which is as short as possible.  You may not fully appreciate it in the beginning, but every decibel makes a very big difference in the number of stations who will be able to contact you, especially if you are using a small antenna and/or have less than 1000 watts in the shack.  If you are running only several hundred watts, don't give up by any means - there are many stations around the world who have made numerous contacts at those power levels; it just means it is even more important to reduce your feedline losses.

3. PHASING LINES - The same advice is true for the antenna phasing lines as for the main transmission line - the lower the loss, the better!  Remember, this is all line loss AHEAD of your preamp, and can affect your signal to noise ration quite dramatically.  Nowadays, there are many choices in low loss feedlines.  I used free surplus CATV 75 ohm hardline (3/4" diameter) for my phasing lines, and the cost (as well as low line loss) is still tough to beat.

4. RELAYS - You will need two relays mounted at the antenna, preferably right on the power divider, to reduce losses ahead of the preamp.  The main antenna relay should be capable of handling high power and switches the antenna between your transmission line and the second (preamplifier) relay.  This relay is ideally the "center off" type.

The preamplifier relay should be a high isolation type (Transco "Y" relays are very widely used for this application) which will switch the preamp between the main antenna relay and a 50 ohm termination resistor.  This relay should be of a type and wired so that the preamp will be terminated into the 50 ohm load whenever the transmitter is on OR the station is not in operation; in other works, this second relay should be energized for receive.

Make sure your relay contacts are clean to avoid additional receive losses ahead of the preamp.  Also be certain that the relays are closed before power is actually applied to the transmitter; no relay or preamp will last very long if the relays are "hot switched".  If your main antenna relay does not have an extra set of contacts on it to control your amplifier, you should build a simple RC time constant or relay sequencing circuit to insure that the coaxial relays have time to close before power is applied.  At my stations, I always have wired my key through a relay (switched after the antenna relays) to make sure that accidentally bumping the key will not key the transmitter and "hot switch" the relays.

5. GROUND GAIN - If you are located on level ground, have a horizontally polarized antenna, and have a flat, clear horizon, you will probably enjoy a certain amount of "ground gain".  This comes from additive reflections when the moon is near the horizon, and can amount to as much as an extra 6 db in signal strength.  Obviously, if you have a small station, this may be the only way to develop enough gain for successful moon bounce contacts, and you should therefore try to take advantage of ground gain by operating during the hour after moonrise and the hour before moonset.  Below is a picture showing my computer screen while DXpedition station  R1MVA (operator was very experienced EME operator, Alex, RU1AA) was sending "R73" at the end of the contact.  R1MVA was only running 150 watts, but they did have excellent ground gain out over the ocean on their moonset.

6. POLARITY - On 144 MHz, practically all EME stations use linear polarization, so you should too.  If you are using a circularly polarized OSCAR antenna for your first EME attempt, signals (transmit and receive) will be 3 db better if you switch to linear polarization before trying EME.  There are very few EME stations big enough to be able to afford to disregard the chance to improve both receive and transmit signals by 3 db!

Radio signals at 144 MHz  being sent to the moon and back are rotated in polarity as they pass through the earth's ionosphere (both coming and going).  This phenomenon is known as "Faraday rotation".  Usually, the polarity or the signals being transmitted will "rotate" around over the course of 30 minutes or so, to match the polarity of the transmitter antenna again.  Obviously, when signals are at a polarity that are different than the polarity of the receiving antenna, signal reception will be degraded.

Some stations have had very good success by using antenna arrays in which the entire array can be rotated to follow the changing polarity due to Faraday rotation.  Others have constructed antennas with elements in both the horizontal and vertical planes, so they can switch between them, to choose whichever antenna best matches the polarization incoming signal.  While these types of antennas almost always provide faster completion of contacts (because waiting time for Faraday rotation is eliminated), most stations opt for the simpler approach of simple, horizontally polarized antennas, and they simply wait until the Faraday rotation (and other variables) match up.

7. OPERATING TIMES - Because the moon moves closer (perigee) and farther (apogee) from the Earth during the course of each month, there is about a 2 db difference in signals attributable to the distance alone.  You will generally be more successful on moonbounce if you operate near perigee.

Another consideration is the background sky noise.  The sky behind the moon is not always quiet and, at times (particularly during the part of each month that the moon is further south in the sky), it can be extremely noisy.  The quieter the sky behind the moon, the easier it will be to hear moonbounce signals. The quietest time is generally just after the moon passes through its most northerly declination for the month and is moving southward in the sky.  Of course, if the moon is too close to the sun, it will also be too noisy to operate successfully and for that reason most stations avoid operating within one day of "new moon".

The moontracking program I wrote for this purpose (TRACKER) shows approximate background sky temperature, moon distance, and the db equivalent sum of their degrading effects.  This makes it easy to select times when the chances for success are more likely.

8. MOON TRACKING - Even if you cannot elevate your antenna, and can only operate on moonrise and moonset, knowing where to point your antennas so they are aimed at the moon is very important.  Most stations use computers to calculate the moon position so they can operate whether the moon is visible or not.  In 1973, I wrote a simple computer program to provide this information and there are now many version of this program for all kinds of small personal computers.  If you have a small computer or know someone who does have access to one, you should have no problem locating a version of the program which will run on that computer and provide you the aiming information you will need.  This DOS program, TRACKER, has been updated over the years, and is available free of charge from my web site.

9. DOPPLER SHIFT - Doppler shift is not that critical at 144 MHz, but you certainly want to make sure to tune up 1000 Hz or so when the moon is rising at your QTH, and look for signals down about 1000 Hz lower than the "schedule frequency" on your moonset.

10. PATIENCE - Please do not become discouraged and give up!  There are many additional factors involved, such as ionosphere absorption, faraday rotation, scintillation and libration fading, which all may sound very confusing.  Basically, it all means that there are lots of reasons why a station may not hear you at the same time you hear him, or why you may not hear anything at all on a given day.  Conditions change, however, and your results can be entirely different later in the day or on another day.

11. SEQUENCING & SCHEDULES - Make sure that you use the proper QSO procedures and transmitting sequences.  On 144 MHz, unless otherwise specified, EME schedules use 2 minute transmit periods, with each station alternately transmitting for full 2 minute sequences.  Because Faraday Rotation typically takes 20-40 minutes at 2m, most schedules are run for a full hour period, to try to provide for at least one polarity peak for each station.  Following the table below can help keep you in the right sequence:

(numbers shown are minutes after the start of the hour)


12. EXCHANGES & REPORTS - Because of the relatively weak signals, CW is used exclusively for EME schedules on 144 MHz, and usually speeds between 10 wpm and 15 wpm work best.  Faster speeds cause the dots to get lost in the fast fading and slower speeds don't let both callsigns be received during slower QSB.  To make sure that you take advantage of the QSB signal peaks, you should always send callsigns alternately, rather than repeating the same callsign. For example, a proper transmitting sequence during a schedule would be filled with "VE7BQH de WA1JXN   VE7BQH de WA1JXN   VE7BQH de WA1JXN" -
NOT "VE7BQH VE7BQH VE7BQH de WA1JXN WA1JXN WA1JXN".  If you are answering a CQ, best success is usually had by sending your call 3 or more times for every time you send the callsign of the station you are calling.

The only signal report usually used on 144 MHz is a letter "O".  When a station hears both callsigns being sent, he responds by sending O's alone during the last 30 seconds (25%) of his 2 minute transmitting sequence.

When a station hears both callsigns and O's, he would respond by sending a full 2 minutes of "RORORO".  When RO's are received, the other station responds by sending a full 2 minute sequence of "RRRR".  The contact is complete when final R's are received by one of the stations.

13. EMAIL REFLECTOR - You can be instantly in touch with EME operators all over the world (and be able to read discussions relating to EME) by subscribing to the MOON-NET email reflector.  Information about this service is located on the MOON-NET Help Page .

14. TWO METER EME NET - In addition to email, real-time activity "spotting" pages, and email "reflectors", the 2M EME NET continues to meet every Saturday and Sunday at 1700 UTC, on 14.345 MHz.  Newcomers to EME communications are welcome and invited to check in to set up schedules, or obtain answers to their questions.

15. COMPUTER PROGRAMS TO COPY WEAK SIGNALS - As illustrated in the SECTION 5 above, computer programs are available to assist in finding weak CW signals.  The program illustrated is AF9Y's  FFTDSP  program.  Another excellent program, which has a built-in audio filter, is HAMVIEW by I2PHD and IK2CZL.

If you follow the above guidelines, you will be well on your way to a good start on 2 meter EME and will discover that moonbounce is not so mysterious and difficult after all! Best wishes and good DX!

Page last updated 10 September 2003