ATTENTION!  NEWS ALERT!
INTRODUCTION OF WSJT'S JT44 AND JT65 MODES REVOLUTIONIZE
6M DXING BY MAKING EME PRACTICAL!

Until the spring of 2002, 6m EME was a rare occurrence, and required big stations (tweaked to highest performance) on each end of the circuit.  Even then, CW signals were extremely weak, and contacts were very rare and unpredictable.  The problem has been that making simple 6m EME contacts has been just barely out of reach for amateur sized stations.   However, with the new WSJT modes of JT44 and JT65, all that has changed.  These are new digital modes of communication that utilize a computer to generate precisely encoded messages that are sent out through the transmitter's microphone as AFSK transmissions.  Similarly, the sound card in the computer processes incoming audio signals from the station receiver, and decodes the messages.  This provides an enhancement of 10 to 16 dB compared to a weak CW signal!  So, where stations were just barely at the threshold of making EME contacts on 6m before, the extra dB provides a SUBSTANTIAL MARGIN FOR SUCCESS!!!  No longer are we constrained by the vagaries of the solar cycles, low solar flux, or locations in high geomagnetic latitudes!  Regular 6m contacts are possible via the moon!  For more background, please see my page, "Welcome to 6m EME".

The new JT65A mode has demonstrated even more sensitivity than the initial JT44 program.  I encourage all 6m stations everywhere, who are interested in DXing and weak signal communications, to try the new JT65A mode of communication!  Certainly, unless one or both stations have large antennas, the "ground gain" from an antenna pointed at the horizon will still be necessary on at least one end of the contact.  And if one of the stations has a horizon looking over salt water, that makes all the difference, since the extra ground gain will really be noticed on EME!

HOW BIG A STATION IS REQUIRED?

What is a "typical" station size now for completing a 6m EME contact?  My first JT44 EME contact was with ZS6WB, who was running 400w output and a single 9 element yagi (M2 6M9KHW).  The contact was an easy one, and I made it while I was pointing up in the sky (no ground gain on my end).  What that means is that two stations, each with good receiver preamplifiers, running 400w, and using 6M9KHW antennas should be able to work each other while the moon was on the horizon at the same time for both stations (so they each had ground gain).  The lowest power station I have completed with so far was running 100w output, with a 5 element yagi.  Most of the JT-- EME  contacts I have had are with stations using around 600 w and a 6 element yagi.

If you can hear your own CW echoes on the horizon, then you can definitely work similarly sized stations.  And there are many stations around the world with good yagis on 6m!  Can the stations be smaller than this?  YES - FOR SURE!!!  With EME, one station can "make up for gain" at one end of the circuit by having a larger antenna.  And remember, you can complete with stations on JT65A that you cannot even hear on CW!

ANTENNA ELEVATION IS NOT REQUIRED!

Fortunately for all of us, most 6m stations have single yagi antenna systems.  I shudder when people get interested in working DX via 6m EME and think they will "make a commitment" and put up a couple small yagis near the ground so they can elevate them.  I am afraid they would quickly become discouraged after they found they could no longer hear anyone!  The secret to success (unless they are planning to put up something like 4 x 6M5X yagis or larger) is to UTILIZE THE GROUND GAIN they have by pointing on the horizon!  I try to explain this to everyone, but many hams don't seem to realize that their single yagi stations act like 4 yagi stations ONLY WHEN THE ANTENNA IS POINTED AT THE HORIZON!  They can have twice as much fun with a single yagi on the horizon (instead of a stacked array) because of the multiple windows afforded by the first and second ground gain lobes. For example, just compare the typical vertical antenna patterns of the 6m arrays here at W7GJ (single yagi at 70' above ground, and four yagis at 32' height), when both are pointed at the horizon.  Note that the single yagi has TWO very high gain lobes, whereas the stacked array really only has one.  So the single yagi fixed on the horizon, provides TWICE as many chances to line up with the moon, as the moon sets or rises and passes in front of the antenna lobes.

And since these ground gain lobes move in alignment with other stations over the course of a month (the moon's declination goes through a complete cycle each month), the moon's movement automatically provides some degree of "steering" to match horizon windows with other DX stations far away.  For the simplest success working DX off the moon, I recommend starting with the LARGEST SINGLE YAGI possible, put up AS HIGH AS POSSIBLE.  As more and more stations become involved in 6m EME, and there are an increasing number of large arrays constructed, then it certainly will become possible to make contacts with smaller steerable arrays (just as has happened on 2m EME).

EXAMPLE OF ACTUAL RESULTS

If one station has a larger system, then they can make up for the gain that is lacking in a smaller system.  For example, I have completed with a number of 100w single yagi stations during their moonsets.  Perhaps it will even be possible to complete with a smaller station!  As an example, just look at the photo below, showing several sequences of solid copy from me while I was running a JT44 sked with ZS6EZ on June 16, 2002 - as monitored by ZR6DXB with his single 5 element yagi pointed at the horizon:

Signals from W7GJ while running with ZS6ES

IMPORTANCE OF A GOOD RECEIVER OR PREAMP

One limiting factor, however, is the sensitivity of the receiver at the station with the smaller antenna.  Even running 1500w on JT65A, I cannot make up for a station with a very poor receiver noise figure AND a very small antenna.  It is absolutely INCREDIBLE what a difference a good 6m preamplifier makes when added in front of practically any commercially available receiver or transceiver for 6m!  For example, I found that my old IC706 (original Mark I version) needs to have a 20 db gain GaAsFET preamp ahead of it, just so I can hear the no-signal background noise at the S1 level!!!  Please see my 6m EME tips page for more information, but remember that everything is now much much easier with JT65A than with CW!

STEPS FOR GETTING STARTED ON JT44

1. INTERFACE.  Build or purchase an interface unit to properly key your rig from your computer and connect the audio lines from the computer sound card.  This is exactly the same as if you were getting set up for PSK31.  The simplest thing to do is to order a "RIGblaster PLUS" from:

West Mountain Radio

You will have to configure this unit with jumpers for your particular radio, but it is easily done.  It includes the cables you will need.  The RIGblaster PLUS model also is very easily modified to also bring out a separate PTT line to activate a sequencer or turn on an amplifier.  Please contact me if you would like information on how to do this.

If you want to build your own interface, you will need to make the serial port cable from your computer be able to key the PTT line of your transmitter (using the RTS line is recommended).  Information about serial pin numbers can be found in any recent ARRL Handbook, or on my station web page.  You also must isolate and attenuate the audio from the computer sound card LINE OUTPUT, so it can be connected to the XMTR MIC INPUT.  Information on how to do this can be found many places (it is the same as for PSK31), but the VKE User Manual found here is a very good reference:

 VoiceKeyExpress Digital Voice Keyer

And finally, you will have to split the audio output from your RCVR, and run an audio line over to your computer sound card LINE INPUT.  This will permit your computer to also hear your receiver, and process the signals coming in.

2. TIMEKEEPING.  Download a program onto your computer to automatically set the computer clock to proper time and keep it there.  The most popular program for this is "Dimension 4".  You can download it for free from:

Dimension 4

Install Dimension 4 so it will check the time whenever you sign onto the Internet, and then every 5 minutes or so that you are connected.  It is important that you select one of the time servers that will provide ACCURATE AND RELIABLE time corrections to your computer from your particular location and internet connection.  You can verify that the time has been properly set within a half second, by listening to WWV and watching the seconds display on the Dimension 4 program screen.  If the time server you select doesn't seem to match WWV, or there seem to be corrections >.1 second when you repeatedly manually set the time with Dimension 4, try selecting a different time server from the optional list provided.

3. GET JT565A MODE COMPUTER PROGRAM.  The exciting new JT65A mode is one of several weak signal digital modes available in the WSJT computer program.  It is available for free from:

K1JT'S WSJT DOWNLOAD PAGE

If you are new to WSJT, or JT65A, you will want to download the entire program from the option "Full Installation of Version ____ ".  Be sure to print out the installation and user manual.

4. RIG SETUP.  Make sure your transmitter is set to USB position, and that the RCVR is set to the widest filter width.  If you have bandpass adjustment on your receiver, make sure it is set to pass tones from 1200 Hz - 1800 Hz (usually this means turn the bandpass knob off or straight up).  I usually recommend using your noise blanker, but turn off the AGC. Turn on the COMPRESSION on your microphone, to insure that you fully are sending each of the tones at full power.

5. OPERATION.  Basically, everything is covered in the manual.  However, here are a few of the quick tips:

Under the "Setup" tab, select the serial COM port number you are using (the one connected to your interface or RIGblaster unit).  Then under the "Setup" tab, set the Options to show your callsign, grid locator , UTC offset, frequency (50 MHz), RX delay (make as low as possible, but still avoiding seeing any spikes at the beginning of the green line - usually .2 seconds if OK as a starting point) TX delay (the default of one second is usually fine for most applications). The ID Interval is left at 0.  Under "Setup" tab, you also need to select what serial line is keying the rig - the default with RIGblaster is RTS, so if that is what you are using, make sure to just check RTS.

When you first start WSJT, it defaults to the meteor scatter mode, FSK441. Therefore, you will have to select "JT65A" under the "Mode" tab.  More information and examples can be found on my "JT65 Checklist" page.

REMEMBER - the only way JT65A can be used to FULL advantage (to gain the last 6 dB it has to offer) is by averaging multiple transmission periods. You MUST make sure to transmit and receive EVERY SEQUENCE for the entire sked!  You cannot just tune by the frequency from time to time to see if the band is open and you "hear" something!  The moon is ALWAYS OPEN (although the Faraday rotation and other phenomena may not permit you to hear something at that particular time).  Because the polarity of EME signals is rarely reciprocal, the other station may be copying you even when you are not hearing anything from them.

6. SKED TIMES.  If a station has a single yagi pointed at the horizon, the elevation of the antenna lobes is determined by the height of the yagi above ground, and there are usually at least two very good lobes that will product successful contacts.  The main lobe is usually between 4 and 8 degrees and the second lobe up (almost identical in the amount of gain) is up between 11 and 15 degrees elevation.  It is recommended to start the EME sked in time to take advantage of the moon passing in front of both these lobes.  This provides additional chances for the polarity to properly line up while the moon is in front of an antenna lobe.  Remember, both stations may not copy each other at the same time, so it may take a couple of passes through the antenna lobes of the moonset station in order for all the messages to be exchanged for a successful contact.  Of course, best results are obtained when skeds are run on the most optimum days of each month (when the moon is closest to earth and not in front of a noisy area of the sky).

OTHER LINKS

All the latest WSJT programs and information can be downloaded for free at:

http://www.physics.princeton.edu/pulsar/K1JT/Download.htm

A good introduction to what it is and what you can do with it is on:

http://www.qsl.net/w3sz/JT44.htm

Many examples of what incredible things are possible using JT44 on 6m, are shown on:

JT44 a new mode for the future de ON4ANT

A real time web page for answering questions and setting up skeds is at:

JT65 EME LINK CHAT PAGE

Additional information and links regarding JT65 use at higher frequencies, as well as timing options, can be found at:

W6/PA0ZN, Rein Smit's JT44 Page

If you want to download your own moontracking software so you can see what times
would work best between two stations (where one or both of the stations are simply aiming at the horizon), my GJTRACKER software is free from my web page:

GJTRACKER BY W7GJ

LET'S WORK SOME NEW COUNTRIES ON 6M!

If you have a preamplifier and are QRV with JT65A on your computer, I would very much like to try to contact you on your moonrise or moonset!  It will be very interesting to learn what the capabilities are of this fantastic new mode of communication!  The Magic Band just learned a new MAGIC TRICK with JT65A!!!

Good luck on 6m EME with JT65A!!!  VY 73, Lance W7GJ
 
 

This page last updated on 12 January, 2009