CONSIDERATIONS FOR
SUCCESSFUL 6M EME
DXPEDITIONS


By
Lance Collister, W7GJ, Frenchtown, Montana
July, 2005



        M2 6M7 Antenna at OX3LX, March 2005.  Photo courtesy of OZ1DJJ

I.    INTRODUCTION

Until only a few years ago, the prospects of completing a 6m contact with a rare DXpedition or portable station using the moon were extremely remote.  However, the increased sensitivity of the recently developed JT65 digital modes by K1JT greatly enhances the viability of such "Ultra Long Path" contacts.  It is assumed that JT65A mode will be a key element to success in any 6m EME DXpedition, and also that interested 6m EME operators are already familiar with this mode.  The standard mode for communications on 6m EME has become JT65A, which is the most sensitive of the JT65 modes.  Detailed instructions of how to effectively use the WSJT software for JT65A EME contacts are available elsewhere and will not covered again here.  New JT65 users are urged to review the following sites:

http://www.bigskyspaces.com/w7gj/JT65checklist.htm
http://pulsar.princeton.edu/~joe/K1JT/Documentation.htm

Our current time near the bottom of the solar cycle is the optimum time for 6m EME, and the amount of activity on 6m EME has been increasing dramatically.   Remember that an EME station with a larger antenna  essentially "makes up for" a smaller antenna on the DXpedition end of the circuit.  Therefore, the increasing number of larger home stations (both with and without elevation) greatly increases the chances for success by a smaller DXpedition station, provided certain considerations are addressed well in advance.   In fact, the portable 6m EME station now can probably fill up as much time as is desired on EME contacts, within the constraints of available moon time.


6m EME array at W7GJ (4 x M2 6M9KHW fed with 1-5/8" Heliax)

This is by no means to suggest that 6m EME is commonplace or trivial.  In fact, nothing could be farther from the truth!  6m remains one of the most difficult bands on which to operate moonbounce, and the situation is exacerbated by the fact that 50 MHz signals are high enough in frequency to be affected by tropospheric ducting and low enough to be adversely affected by just about any kind of perturbation in the ionosphere.  And, of course, even when conditions are most favorable for EME, you always run the risk that Faraday rotation will change the polarity so that one (or both) stations will not be able to copy the other!  This polarization shift is what makes it very rare for two stations to be copying each other at the same time, and is the reason why EME schedules are often so long - to permit each station to have a chance to exchange required contact information with the other.


M2 6M7JHV yagi installed above the Jersey Amateur Radio Club in May 2005.  Photo courtesy of GJ8BCG

Certainly, if you are a DXpeditioner strictly for numbers of contacts with the simplest equipment, HF is a much more attractive option.  However, if you enjoy the challenge as well as the reward in overcoming the odds and completing contacts by sending signals 3/4 million kilometers, then you are just the type of DXer for 6m EME!  I have always thought of EME DXing as having much in common with fly fishing.   If your primary interest was to obtain large numbers of fish, you could drive to the fish market.  However, if you were more interested in relying on yourself, in a way that will require all your skill and cunning, then fly fishing will be more thrilling and rewarding - even if some get away!  Like fly fishing, it is the challenge of the adventure and the process - plus the thrill of actually landing one - that makes it so rewarding!


FT5XO 6m antenna (M2 6M7NAN "Trip Yagi").  Photo courtesy of W7EW, March 2005

There are a number of different approaches that can be used by a successful 6m DXpedition station, and it is not my intent here to attempt to prescribe any single protocol which has emerged as being most successful.  Because this is such a new corner of 6m DXing, we are all learning from the experience of each DX operation.  However, there are definitely certain subject areas which will need to be considered prior to embarking on a successful DXpedition, and I hope to discuss a few of these elements that are particularly relevant to 6m moonbounce in order to assist stations thinking about preparing for 6m DXpeditions.  I also will  suggest some possible operating options that have come to light through recent 6m EME DXpeditions, that might be used to increase effectiveness during future operations.

II.    PLANNING

Certainly, the first thing to consider when you are selecting a location to set up for a 6m EME DXpedition is to find a good quiet location.  For most of us, the local noise that surrounds us where we live is something beyond our control.  There are many people who live in urban areas who constantly struggle with high noise levels, and cannot imagine adding a preamp to make their receivers sensitive enough to copy weak signals on the 50 MHz band!  Certainly, one of the advantages offered by a chance to set up a portable EME station is the possibility of finding a place to avoid the high noise that plagues so many stations on the "Magic Band".  Ideally, you will be able to find a spot that will not require you to aim the antenna toward high power RF transmitters, industrial areas, noisy street lights, power lines or other noise sources that will mask weak signals.

If you are planning to limit your EME operation only to the horizon, you also will want to make every effort to locate the station in as favorable a location as possible for the best possible ground gain.  Usually, this means finding a clear, flat area, free of "ground clutter" (hills, boulders or man-made objects such as houses, cars, etc. that can deflect ground reflected signals away from your antenna).  The best terrain for ground gain is salt water, although fresh water (such as a large lake or marsh area) or flat open ground also has been shown to work incredibly well.

Quiet location with excellent ground gain, as proven by 7P8NK in August 2004.  Photo courtesy of VA7DX

When aimed on the horizon, the vertical pattern of a single yagi antenna becomes a series of sharp, high gain lobes and deep nulls due to ground reflections.  For most small stations, one of the most critical elements in the equation for making an EME contact on 6m involves taking advantage of this extra "ground gain".  Indeed, with a good, flat clear area in front of an antenna (unobstructed by a roof, HF antenna below the 6m beam, etc.), the ground gain of an antenna leveled on the horizon often makes a well located single yagi perform like an array of 2 or 4 yagis - at least when the moon happens to move in front of one of these lobes.  The shape and elevation of these ground gain lobes depends on the gain of the antenna and its height above ground.  Generally speaking, ground gain lobes are broader with lower gain antennas and lower height, although the lobes from such antennas also are higher in elevation and comparatively weaker. 



Vertical (H plane) plot of single yagi at W7GJ, courtesy of K0GU



6M7JHV yagi during the J68AS DXpedition June 2005.  Photo courtesy of W8QID/J68ID
For a single yagi antenna at a typical "DXpedition height" (around 20' above ground), there is usually a good second ground gain lobe up around 15 degrees elevation.  The quality of the higher ground gain lobes will depend more on the condition of the terrain in the near vicinity of the antenna in the direction toward the moon, and that is one reason this lobe often seems to be more effective than the "main ground gain lobe".  It is much easier to have some control over the terrain a few hundred feet in front of the antenna compared to the landscape many thousands of feet away!  Therefore, if you have the chance to set up by a lake or sea, it is definitely advantageous to be as close as possible to the water.

Of course, if you have the good fortune to be able to overlook a large lake or sea so that your most distant horizon is water, you will certainly also has a negative horizon, just from the curvature of the earth.  In such a case, you will find there is a "bonus ground gain lobe" located around zero degrees elevation.  Be sure to use this extra ground gain lobe to advantage, and by all means plan to operate when the moon is down as far as negative 2 degrees!
The OM3RCC EME operation (a DXpedition by OK1TEH) used only a small station, but they had a relatively smooth grassy area that sloped up away from the antenna toward their moonset.  This made the ground gain lobe higher in elevation than would be expected for a single yagi up at 20' above the ground, but still very effective.  A complete story about the DXpedition can be found here.

Just as important as locating your own station to maximize your own ground gain, it is important to look at the times when other stations will have ground gain to coincide with yours.  This is especially important for smaller stations and/or stations limited to the horizon (either because they have no elevation, or because they have only very limited common moon window with you).  The first assumption often is that there must be very little chance of being able to work another small horizon-only station.   However, upon closer examination, one often can  find a number of potential common moon windows when both single yagi stations will have ground gain!  Remember that you probably will have first and second lobes on both moonrise and moonset (perhaps plus an additional "zero degree" lobe due to a negative horizon), each of which provide an opportunity to match up with one or more similar lobes at the other station.

As you explore possible contacts, remember that the moon changes in declination every day, so new common moon windows are opened up with different horizon-only stations each day.  As you plan your trip, you may also want to look at the times of day for your moonrises and moonsets.  For example, if you are going out during a time of year prone to Es, F2 or TEP, you will want to pick dates affording windows in directions and at times of day least likely to be interfered with by these ionospheric propagation modes.

I0JXX 5 element yagi at OM3RCC during the DXpedition August 2007.  Photo courtesy of OK1TEH.
Generally speaking, any disruption of the geomagnetic field/ionosphere will have an impact on 6m signals. Even if the MUF is not high enough to produce effective ionospheric propagation at 50 MHz, the chances are quite good that signals can be deflected off their direct course toward the moon and back to you on earth.  So, ideally, one would avoid periods of expected cyclical disturbances (such as recurring 28 day coronal holes).  However, the exact timing of these types of solar events often are not known with the same accuracy months in advance, the same way reliable Es, F2 and TEP seasons can be predicted.

In addition to the above mentioned ionospheric considerations, there are two additional factors which can play a large role in the success of a 6m EME operation. Luckily, these are related to the moon's orbit, and are very predictable.  The first is distance to the moon, and the second is the sky temperature (noise) of space behind the moon.

As you know, the moon orbits the earth once every month, and as it does so, it appears to move up and down in the sky. The moon therefore appears to pass through various spots on the celestial sphere, some of which are quiet, and others that are extremely noisy down at 50 MHz.  And of course, you generally also want to avoid days of the month for "new moon" since the noisy sun will be very close to the moon then.  When the moon moves in front of a noisy place in the sky, trying to copy a weak EME signal is just as difficult as trying to hear someone whispering to you from across the room during a noisy party.

 In addition, the moon moves closer and farther away from Earth over the course of its orbit each month.  This change in distance alone causes a change in signal strength of about 2 dB.  The combination of these two factors is commonly referred to as signal "degredation".  Degredation is typically expressed as an index in dB, as compared to the ideal situation in which the moon would be at perigee (closest to the earth) at the same time as the sky behind it was quietest.  One would definitely want to plan a 6m EME operation during a time of month which affords the least amount of this degredation.  These degredation figures (shown in real time on the JT65 operating screen) are also available in several of the popular moon-tracking computer programs available for use in planning purposes.  One such free program that is still used by many EME operators is available here:  http://www.bigskyspaces.com/w7gj/tracker.htm

Unfortunately, the minimum degredation down at 50 MHz may not be much lower than a couple of dB, because perigee may not happen at the same time as the moon is in a quiet part of the sky.  These two conditions move slowly in and out of sync over a period of years.  Typically, the 6m degredation fluctuates between one or two dB and over 10 dB over the course of a month.  If you have been keeping tally, you will notice that there are many factors that can reduce the already very marginal signal strengths on 6m EME!  Obviously, when signals are just at the threshold of being detectable under the best of conditions, even just a dB or two makes a very significant difference!  This may all begin to sound like an impossible game to win!  However, with careful planning, the chances for success can be greatly enhanced. 

III. EQUIPMENT

Perhaps one of the most fundamential elements of a 6m EME station is a computer with an interface to connect it to the radio, thereby providing digital capability.  An equally important requirment to operate in JT65A mode is to ensure some way to maintain accurate timing of the internal computer clock.  The reliability of internal clocks in most computers - especially laptops - are usually quite poor.  Ideally, one would like to be able to maintain half second accuracy at least over the course of an hour long schedule.  If internet access is available, there are very popular programs  (such as Dimension 4, Tardis, DXTIME, or Atomic Clock Sync ) which can be used to automatically reset the computer clock at a selectable interval (such as every 5 minutes). 

If there is no internet available, the most common way to keep the computer clock accurate  is to use a GPS unit plugged into the computer running a program such as NMEATime or the free GPSTime.  In the event that neither a GPS unit nor internet is available, the computer clock can always be set fairly closely by ear using WWV, and fine-tuned by adjusting the DSEC control on the JT65A screen until the displayed time closely matches that transmitted by WWV.  (Such manual timing would have to be checked regularly, though!)  This last method was the resourceful technique utilized by operator N9AB to complete the successful contact from J68AS for W7GJ's 100th country on 6m!

Another important piece of equipment is an amplifier.  Outstanding results have been achieved by stations using the ACOM 1000 amplifier (kw on HF plus 6m) on 6m EME DXpeditions, but other types of amplifiers with at least 400w output can also be quite successful.  Note that even a 400w amplifier has 6 dB gain compared to a 100w transceiver.  That 6 dB makes a huge difference when signals are just barely discernable, as they usually are on 6m EME!

Of course, it also is very important to make sure your amplifier can withstand the roughly 48 second full duty transmit periods of JT65 mode.  Usually, the addition of an extra blower or fan to increase the airflow will permit full power operation for this amount of time.  Here at my station, I use a pair of high volume fans to suck the air out of the plate compartment on my amplifiers.  This reduces the back pressure on the blower and greatly increases air flow through the tube.  With this simple addition, the exhaust only becomes warm - not hot - by the end of the full-duty JT65 transmit sequence.

Another very helpful accessory is a preamplifier for the receiver, although many people have completed 6m EME contacts without an external preamp.  With most commercial transceivers one will definitely notice the improved noise figure of an external low noise preamplifier - especially if operating during an optimum time of month (low degredation factor) from a quiet location.  As long as there is low feedline loss (less than 1 dB), the benefit from such a preamp will be just as effective if it is installed right in front of the receiver, and that is they way they are used at most 6m EME home stations. 

Very popular preamp among 6m EME stations worldwide is the CA50T preamp, which features a PHEMT device for high dynamic range as well as very low noise figure.  It is available through the manufacturer, LNA Technologies:

http://www.lnatechnology.com/lnatech_015.htm

They also have a new RFCA50T model that is RF switched and can be installed directly between the amplifier and a transceiver.

Addition of fans to reduce blower back pressure on W7GJ's amplifiers
Regardless of the type of antenna used for a DXpedition, it is very important to use good quality feedline.  The loss in the feedline will be very critical on both receive and transmit, and one of the advantages offered by a DXpedition operation often is the ability to set close to the antenna, so only a very short piece of coaxial feedline is required.  The availability of  low loss coax such as LMR600 has been a tremendous asset in optimizing 6m EME stations:

http://www.timesmicrowave.com/content/pdf/lmr/28-31.pdf

Various types of  antennas have been used successfully on 6m EME operations.  As already discussed, the performance of a small antenna can be greatly enhanced through the use of ground gain.  Most successful DXpeditions have used a single, good computer-optimized 6 or 7 element beam.  You can view some such antennas on this page, and with more examples here:

http://www.bigskyspaces.com/w7gj/6mEMEstns.htm

There are several good reasons for using the largest possible single yagi.  If the antenna is going to be aimed on the horizon, a single yagi will generate multiple good ground gain lobes, providing more opportunities to complete contacts.  In addition, the second ground gain lobe generated by a single yagi is often more effective than the lower "main" lobe, simply because it is aiming higher, through less atmosphere/ionosphere, and is less subject to tropo ducting and/or interference from ionospheric factors.  Another feature in favor of a larger single yagi mounted as high as possible is that it will be higher and have a lower main lobe angle of radiation, compared for example, to a pair of smaller yagis stacked vertically.  In some cases where moon windows are very limited, it may be very desirable to try to maximize the signal as low to the horizon as possible. 



7 element yagi at LA8AV/OH0JFB June 2004.  Photo courtesy of OH0JFB
And, of course, it is mechanically much more secure for a portable operation to erect and guy a single yagi as opposed to a vertical stack.  If the object is to generate the most gain, a large single yagi aimed at the horizon is the easiest way to do it!

Mast bracing and antenna rotating is also most easily accomplished with a single yagi.  If the azimuth and readout is manual, a very effective method I have used on DXpeditions is to bury the mast in the ground (resting upon a solid object such as a board or concrete block if the ground is all sand) or set it on a plate, with a protractor around the mast.  An indicator such as a bent paper clip taped to the mast is a very accurate and simple indication of direction.


The following photos of M2 6M7NAN "trip yagi" installations shows how the mast can be guyed effectively to withstand even high winds.  Notice how the antenna at FT5XO is held at the desired azimuth by the two lines which are connected to the rear of the antenna.  These lines can be either tied to fixed objects, or heavy moveable objects such as concrete blocks (which can be easily moved around to change the aiming of the antenna).


FT5XO 6m antenna (M2 6M7NAN "Trip Yagi"), March 2005.  Photo courtesy of W7EW


FP/N6RA 6m antenna (M2 6M7NAN "Trip Yagi"), June 2005.  Photo courtesy of N6RA

The advantages of a single yagi having been said, there also are some very good reasons to consider a pair of smaller yagis mounted side by side.  Even though vertically polarized yagis will sacrifice a few dB ground gain when aimed on the horizon, they can be mounted and elevated quite simply to track the moon.  And because of the mechanical arrangement, it is easy to aim the array as high as desired - even directly overhead if necessary!

If a pair of good yagis is used, the free space gain (when the antenna is aimed up off the horizon) can almost be as much as the very brief peak in ground gain generated by a horizon-only antenna.  And, as more and larger 6m EME stations come on the air, portable operations utilizing antennas with elevation will make the best use of the available moon time.

6m EME array of two vertically polarized side by side yagis.  Photo courtesy of NL7Z
An example of how a single long boom 7 element yagi with elevation could be used to expand available moon windows was illustrated by JA1RJU during his very successful May 2005 operation from KH0.  Although the elevation was limited to about 45 degrees elevation, the moon time was substantially increased.  The elevation was manual, with very simple, easily transportable indicators, as shown in these photographs (all photos courtesy of JA1RJU).
7 element long boom yagi at KH0/KH2K

Elevation mount at KH0/KH2K

Elevation indicator at KH0/KH2K
At the end of March 2009, W7GJ activated Rarotonga on 6m EME as E51SIX.  Lance used the 12.2 dBD gain 6M8GJ yagi produced by M2.  The antenna was manually elevated and most of the 28 EME contacts were made when the antenna was elevated above the horizon.  The coaxial feedline was a 50' long piece of Times Microwave LMR600 Ultra Flex with a loss of only 0.3 dB.


M2 6M8GJ yagi at E51SIX  during the DXpedition in March/April 2009.  Photo courtesy of W7GJ.


W7GJ elevation mount showing elevation marked directly on the mount itself.  Photo courtesy of W7GJ.



In August 2011, W7GJ activated Samoa as 5W0GJ.  This photo shows the 6M8GJ installed on the M2 Portable Mast, on the lava flow with the salt water bay immediately to the east for best ground gain during moonrise.

M2 6M8GJ yagi at 5W0GJ  during the DXpedition in August, 2011.  Photo courtesy of W7GJ.






On March 19, 2011, VP8DMH activated Antarctica for the first time on 6m EME.  Mike was unable to set up the antenna permanently but managed to hang it from the piece of maintenance equpment shown.  With that arrangement, he was able to steer the antenna in azimuth and elevation using ropes attached to the rear end of the boom. 

  M2 6M8GJ  during the Antacrtic activation  in March, 2011.  Photo courtesy of M0PRL
One final note about DXpedition equipment concerns filters.  To ensure that the portable operation does not interfere with local TV or other communication services, it is advisable to include a good low pass filter on the transmitter.  In addition, if HF amateur transmitters are being operated nearby at the same time as 6m EME activities are planned, it will be very important to make sure they also have are equipped with low pass filters and good grounds.  In addition, it can be very helpful to have a supply of ferrite beads to clip over audio leads going into and out of the 6m radio and computer, to make sure that HF RFI does not corrupt the audio lines of the EME receiver. 

IV. OPERATING OPTIONS

There are various strategies that can be employed by an EME DXpedition station.  Some of the same considerations apply to JT65 mode operation as also have been used in CW operations.  As with CW operation, it is sometimes helpful to consider split frequency operation (if QRM is anticipated) and it also helps to have the callers on JT65A spread out a little bit in frequency.  Schedules can be set up on one frequency, with random calls always welcomed on another frequency (or, preferably, a small range of frequencies).  As long all the frequencies are not too far apart (no more than 1 KHz), they can be viewed simultaneously on Spectran, and the DX station can determine whether to continue to call the schedule station or to reply to a random caller. 

Since the familiar CW pileup type of operation does not work very effectively with JT65 mode (which does not tolerate QRM well), setting up separate schedules is often preferred.  The biggest problem with this approach is that it ties up large quantities of valuable moon time (which is especially limited if the DXpedition has a horizon-only antenna).  On the other hand, random CQ's will very likely create callers, but often not at the same time when the DXpedition can copy them.

The most productive technique demonstrated so far, is that home stations who hear a CQ let the DXpedition station know they are being copied, so they can run a quick schedule.  In this way, the DX station can sequentially run skeds with stations copying him.  This is quite easy if both stations have access to the internet, but internet is frequently not available from remote locations.

For remote DX stations with which there is no internet contact, it would seem that the only options are pre-arranged schedules or random contacts from CQ's.  Based on results from this year's 6m EME DXpeditions, and previous experience with 2m EME DXpeditions, it generally seems that calling CQ is usually more fruitful in creating successful contacts - at least as far as the DXpedition station is concerned.  However, because both stations may not be able to have extended common moon windows to wait for a suitable situation when a CQ can successfully be answered in real time two-way contact (if such a situation ever indeed arises), there is still a need to accommodate some aspect of scheduling with an individual station.

Although basic JT65 contact exchanges and procedures are based on traditional CW protocols, there are some very attractive new features possible with JT65 that can be utilized to make random DX operation more successful.  These new methods have been tried to a limited extent so far, but with good success.  Obviously, what would be very helpful would be some indication from random callers that they are copying the DX station; otherwise, the DX station can waste much valuable time calling stations that cannot copy him.  One way this currently could be done would be for the caller to send callsigns plus received dB signal strength level.  This could indicate that reception was taking place, and there would be a good chance for a quick contact.  A possible scenario is the following, shown in alternating transmit sequences:

DX STATION XMIT SEQUENCE

HOME STATION XMIT SEQUENCE COMMENTS
W7GJ J68AS

Calls CQ or runs a schedule and sequentially decodes callers using the JT65A FREEZE filter with DECODE button

J68AS K6MYC -24
Answers the DX station with dB reports to indicate that he is copying the DX station at that time.  He sacrifces several dB sensitivity in order to convey this information along with calls.
K6MYC J68AS FK94 OOO
Sees that K6MYC copies so replies to him with standard reports

RO K6MYC replies with standard shorthand confirmation and reports, which are easily recognizable visually to DX on Spectran or the SpecJT waterfall.
K6MYC J68AS RRR
DX acknowledges with final RRR, while still sending both calls so especially K6MYC will know that they have completed, and others will know to whom the RRR is being sent.

73 K6MYC lets DX know the contact is complete, with shorthand message also visible to DX on Spectran or the SpecJT waterfall.
CQ J68AS FK94
DX goes back to calling the schedule station or to sending CQ

There are a few comments are warranted regarding the above random contact.  The first is that K6MYC did sacrifice several dB in sensitivity by sending reports out of sequence to simply indicate that he was currently copying.  A contact only requires 3 minutes, if both stations are fortunate enough to have mutual propagation, so it is important for the DX station to identify stations who are copying him at the same time he is copying them.  If the DX station is making a contact in the middle of a schedule, the above procedure of sending calls along with all the reports and confirmations would enable the contact to be made cleanly without confusion, and the DX station could then return to the schedule or calling CQ.

However, if there is no schedule or contact already underway, the same objective could be accomplished by using standard JT65A messages, without any loss in sensitivity.  The recommended procedure is shown below.  Note that in the example below, K6MYC sends OOO just to indicate he is copying the CQ from J68AS, without any loss in sensitvity compared to just sending calls.  This shows J68AS that K6MYC is a station who is copying him at that time, and could complete a contact with him quickly. 

NOTE:  Sending CQ is a very sensitive message.   If J68AS were sending reports to some other station, K6MYC might not have decoded him unless the signals were -24 dB or stronger.  However, as long as he sees a signal trace from J68AS on the SpecJT waterfall, K6MYC should call him calls with OOO to indicate he is copying.  The reason for this is that if he is seeing a trace - and he has chosen the option to decode the sequences using the Deep Search tool - he will successfully decode incoming sequences when J68AS either returns to CQ or calls K6MYC. 


DX STATION XMIT SEQUENCE

HOME STATION XMIT SEQUENCE COMMENTS
CQ J68AS FK94
Calls CQ and sequentially decodes callers using the JT65A FREEZE filter with DECODE button

J68AS K6MYC OOO
Answers CQ with standard sgnal report to indicate that is copying.  Sending standard OOO reporsts sacrifices no sensitivity compared to just sending calls.
K6MYC J68AS FK94 OOO
Sees that K6MYC copies so replies to him with standard reports

RO K6MYC replies with standard shorthand confirmation and reports, which are easily recognizable visually to DX on Spectran or the SpecJT waterfall.
RRR
DX acknowledges with final RRR, which can be easily decoded by all callers, so they know the DX station is ready to work a new station.

73 K6MYC lets DX know the contact is complete, with shorthand message also visible to DX on Spectran or SpecJT waterfall
CQ J68AS FK94
DX goes back to sending CQ

As long as the home stations all spread out every 200 Hz, the DX station will not see any QRM from the callers, and will be able to decode all the callers, even while working one of the stations.  This spacing ensures that they will not interfere with each other, and the DX station can easily separate them using 50 or even 100 Hz TOL settings with their FREEZE filter.  As long as the stations are spread out in frequency, it is important for all the stations to keep calling as long as they are still copying the DX station.  The DX station will then be able to have another station ready to call with reports as soon as the current contact is completed.  In the above examples,  visually decoding the RO and 73 messages on Spectran or the SpecJT waterfall allows the DX station to focus on decoding other stations and preparing to reply to other callers. 

If skeds are being taken, an arrangement that would appear to work here is for the sked stations to call 200 Hz DOWN in frequency, while all random callers reply HIGHER in frequency, trying to space out at 200 Hz intervals.  The DX station could then clearly identify the sked station (as the only trace with negative DF) and still be able to see the random callers.  To provide an opportunity to practice selecting and alternately decoding stations answering a CQ by using the FREEZE filter, six  files are provided while W7GJ was completing first with K7BV (who indicated he was copying, by sending a dB signal level when he called), and then with K1SG.  These can be downloaded from:

 http://bigskyspaces.com/w7gj/JT65Apracticefiles.zip

The problem remains, of course, that with horizon-only capability, the DX station has little time available to wait for the polarity to rotate in order to complete a contact where propagation is not mutual.  He probably needs to give it a good 20 minute try before going off to call CQ or answer other random callers.  He can always return to the sked station later if he sees him again.  If the DX station has elevation, he is not nearly as limited by a few narrow ground gain lobes, and has the luxury of more time to operate random.  In such a case, it makes sense for the DX station to set up schedules with horizon-only stations and/or stations with limited common moon windows, but also to always watch for off frequency random callers, and to call CQ during any non-sked times.

As experienced JT65 users are well aware, the visual aspect of receiving EME signals is an equally critical element in efficiently operating the station.  Often, it is seeing the presence of calling stations during a receive period that provides the operator the extra time to decide where to set his FREEZE filter to be ready for the decode at the end of the receive period, so he can set his next transmit period accordingly.  Obviously, if he simply visually decodes the final RRR shorthand  message from one station, he can quickly set up to decode another caller instead, thereby being able to decode and reply to the new station before the next transmit period begins.  Similarly, if he sees absolutely no visual trace from the schedule station, but observes another strong station calling slightly higher in frequency, he safely focus on the random caller.  Or, if he sees a trace on the schedule frequency, he can set up to first decode that caller, and try to complete with the sked station.  Callsigns and messages are of course quickly selected automatically by simply double clicking on the caller's callsign.  It is the combined use of the visual waterfall display, along with skilled selective sequential decoding of various signals that will enable the DX station to send the most judicious information, and thereby maximize EME contacts.  You will be able to practice recognizing the appearance of the shorthand messages, as well seeing the different callers, if you download the above practice files.


M2 6M8GJ yagi on M2 Portable Mast at 3D2LR  during the DXpedition in September/October, 2010.  Photo courtesy of W7GJ.

The above procedures were very successfully used when W7GJ operated from 3D2 on a 6m EME DXpedition at the end of September, 2010; EME contacts were completed with 52 different stations, and 17 additional stations were copied but not worked. Excellent results were also enjoyed when using this procedure on 6m EME from 5W in 2011. 


M2 6M8GJ yagi used with manual elevation and azimuth at T32C in October, 2011.  Pictured are 6m EME operators Michael DG1CMZ (L) shaking hands with Mike G3WPH (R) after the first 6m EME QSO.

V.     CONCLUSION


Pair of M2 6M5X yagis at K5N EME grid DXpedition to DL88.  Photo courtesy of K5QE
In conclusion, I can't over-stress the importance of effective planning and some actual pre-trip practice with the JT65A software and the particular equipment assembled for the DXpedition.  With good planning and preparation, you can enjoy the results of  "Ultra Long Path" contacts - even if the 6m band would otherwise appear "dead".  Whether you are planning a DXpedition for meteor scatter, VHF contesting, or HF, I hope you will think about adding 6m EME capability as something special to fill the time when the moon is beckoning.   Here's wishing you a healthy amount of good luck in making some very special "Celestial Magic" on the 6m band!
 
On 6m EME, the Magic never ends...

Photo courtesy of ZS6A






© W7GJ 2005-2012, revised 6 July, 2012