Recommended Procedures for Random Digital EME
Joe Taylor, K1JT
Around the year 2000 a growing number of VHF enthusiasts began experimenting withdigital coding and modulation techniques that show great promise for enhanced weak signal
communications. Early eﬀorts included the computer-aided high-speed CW mode of 9A4GL,
designed for meteor scatter, and a multi-tone frequency-shift keying mode called PUA43,
developed by W7PUA and intended for EME. At about the same time, modes like PSK31(by G3PLX) and MFSK16 (ZL1BPU and IZ8BLY) were becoming popular on the HF bands.
My own software program WSJT was based in part on the pioneering work of these and otheramateurs; my goal was to make the advantages of digital communications conveniently andwidely available to VHF/UHF weak signal enthusiasts. WSJT began seeing worldwide use
for VHF meteor scatter QSOs in mid-2001, and for EME some nine months later. The
presently popular EME mode called JT65 was incorporated into the program in late 2003.
Not surprisingly, the new weak-signal modes ﬁrst gained popularity among a subsetof amateurs who were familiar with computers and digital electronics, as well as being
skilled in VHF/UHF weak signal techniques. The new developments came at a time of
rapidly increasing use of the internet for general communication. As a consequence, technicaldevelopment and popularity of the new weak-signal protocols beneﬁted enormously fromsuggestions, advice, feedback, and other information exchanged via email reﬂectors andinternet chat rooms. Special purpose “loggers” like Ping Jockey Central, the JT65 EME
Link, and the ON4KST EME Chat sprang up to help experimenters coordinate their earlyeﬀorts with the new software. These loggers made it very easy to ﬁnd willing QSO partners
and to make real-time schedules.
I think all of these developments have been good for Amateur Radio, and for theVHF/UHF weak-signal community in particular. However, in this brief note I wish to suggest that there is more to amateur EME operation than simply making pre-arranged QSOs.
Any contact with a fellow amateur using signals reﬂected from the moon is exciting, a significant achievement, and something to be proud of; but it is especially rewarding when a QSObegins with the pleasant surprise of someone answering your CQ without pre-arrangement
through another medium. My goal here is to suggest operating procedures that should help
to facilitate more widespread access to those very pleasant moments of surprise.
Protocols like JT65—and others that will surely succeed it—can enable amateur radio
contacts with signals too weak to be audible. Such signals can’t be found by the traditional
method of slowly tuning the band with the headphones on, listening for weak carriers.
Even worse, for many of us such procedures serve mainly to locate the ubiquitous “birdies”
that plague us in this increasingly electronic age. We are fortunate, however, that digital1

technology has brought us the capabilities of spectroscopic visual aids that make it easy toﬁnd weak JT65 signals in a speciﬁed region of a VHF/UHF band. The JT65 synchronizing
tone, which carries half of the energy of every transmission, is readily distinguishable frombirdies because JT65 transmissions start on an odd or even UTC minute and end about
47 seconds later, with somewhat longer “oﬀ” periods in between. Operators who make theeﬀort to install a software package like Linrad (by SM5BSZ) or Winrad (I2PHD), and thehardware to support it, can have a panoramic view of all the signals in a 90 kHz band
segment and can watch the behavior of those signals over time. With such a system it iseasy to pick out the potentially workable JT65 signals on one’s favorite band.
Most operators use WSJT with a standard SSB transceiver providing a bandwidth oflittle more than 2 kHz, and the waterfall spectral display built into WSJT was conﬁgured
with this limitation in mind. Until many operators have upgraded their stations to include
the capabilities of a wide bandwidth Linrad-like display, random digital EME operation will
be greatly facilitated if we can designate relatively narrow sub-bands where such activity canbe concentrated—standardized “meeting places” where QRV operators can ﬁnd one anotherwithout relying on information from another source. To make my proposal speciﬁc, Table 1
contains suggested sub-bands to be used for random digital EME activity on our worldwide
VHF and UHF bands.
Table 1. Suggested sub-bands for concentration of random digital EME.

Frequency Range(MHz)
50.185 – 50.195
144.115 – 144.135
432.060 – 432.070
1296.060 – 1296.070

As far as I am aware, these suggested frequency ranges conform well with existing
band plans and operating practices in most parts of the world. The center frequencies of50.190, 144.125, 432.065, and 1296.065 MHz are close to the activity centers already being
used for JT65 EME on these bands. The frequencies 432.065 and 1296.065 MHz have helpful
mnemonic advantages, so I have placed them at the centers of suggested 10 kHz ranges which
seem suﬃcient for present levels of activity. On 2 meters, where JT65 EME activity is muchgreater, I suggest a 20 kHz range. In North America 144.140 is used as a calling frequency
for the FSK441 meteor-scatter mode, so I have avoided that frequency. To accommodate
operators in Japan, who are required to transmit JT65 below 144.100, I suggest a secondary
sub-band 40 kHz below the one listed in Table 1, centered at 144.085 MHz. If an operator2

who must transmit above 144.100 ﬁnds a JA station calling CQ on 144.082, I suggest thata reply should be made on 144.122, exactly 40 kHz higher—and vice-versa. Of course, one
should be aware of other (possibly regional) uses of these band segments, and always operateaccordingly. If split-frequency operation is required, such as when working between Japanand the United States on 2 meters, care must be taken not to cause QRM on the transmitting
frequency. Remember that EME Doppler shifts can be substantial on the higher bands—
as much as 3 kHz at 1296 MHz. I believe that the frequency ranges suggested in Table 1
are consistent with present practices for digital EME; if I have overlooked some important
constraint, I trust that a suitable modiﬁcation to Table 1 can be found and agreed upon.
Let us suppose that the worldwide EME community agrees to the suggestions outlinedabove. (The basic ideas have been discussed on the Moon-Net email reﬂector already, withpositive responses.) What other operating procedures could be adopted to help us ﬁnd one
another on the bands and optimize our available time for making digital EME QSOs? I
suggest that in general we should listen ﬁrst near the center of the relevant sub-band. If
this frequency seems unused and is free of local problems, it should be a good place to call
CQ. If the center frequency is busy, or perhaps you have a strong local birdie there, move up
or down in small steps, say 1 kHz. During contests or special activity weekends the whole
sub-band may become busy; in such cases one can move farther up or down from the nominal
center frequencies.
The bandwidth of a JT65 transmission in the A, B, and C submodes is about 178,355, and 711 Hz, respectively. More than 25 JT65B signals can be squeezed into a 10 kHz
window without interference. Moreover, the JT65 decoders cope surprisingly well even when
two signals overlap in frequency. Local interference from another EME-class station canbe a problem; in such cases, the best recourse is usually to transmit in the same sequence(ﬁrst or second) as that used by other stations in your area. When contending with signals
reﬂected from the moon, a bit of QRM can be almost welcome. WSJT can easily decode
several diﬀerent signals that were received simultaneously, and it’s fun to keep track of whoelse is active while you are on the air.
Our operating procedures should be friendly to SWLs and third-party listeners. Aftera QSO is ﬁnished, stay where you are for at least a few minutes, listening for possible tailenders. If you originated a QSO by calling CQ, another station may call when you ﬁnish; if
you answered someone else’s CQ, a third station may want to work you afterward. Common
courtesy dictates that he will probably not call right on the frequency you have been using.
Considering the bandwidths of JT65 signals, I suggest calling up or down by something like
0.5 to 1 kHz in such situations. By the same token, I recommend listening carefully after
your QSOs, both on your own frequency and slightly higher. A future version of WSJT may
increase the available bandwidth by a factor of two or more, if your receiving hardware can
support it. This would make such procedures signiﬁcantly easier.
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Special circumstances sometimes apply to DXpeditions, rare DX stations, and “bigguns” in contest situations—in other words, whenever many stations are simultaneously
calling a single desired station. Under normal activity conditions, minimal JT65 EME QSOs
generally proceed something like the example shown at the left in Table 2. When there isa signiﬁcant chance of confusion about who has transmitted a message or who it may beintended for, callsign-tagged formats should be used for messages 4 and 5, as shown on theright in Table 2. JT65 provides for other message formats, as well, including ones withnumerical signal reports. If you are unsure of the available message formats and capabilities,
refer to the WSJT User’s Guide for details and instructions on their use.
Table 2. Recommended message formats for minimal EME QSOs using JT65.

1.
2.
3.
4.
5.
6.

Normal activity
CQ RN6BN KN95
RN6BN K1JT FN20
K1JT RN6BN KN95 OOO
RO
RRR
73

1.
2.
3.
4.
5.
6.

Pileup situations
CQ 3Y0X EC41
3Y0X K2TXB FM29
K2TXB 3Y0X EC41 OOO
3Y0X K2TXB RO
K2TXB 3Y0X RRR73When designing the standard JT65 message formats, I imagined that the mode might beused in terrestrial VHF/UHF contests where grid locators are part of the required exchange.
In EME QSOs the locators are largely superﬂuous and could well be eliminated. A futureversion of WSJT may provide enhanced performance for messages that contain a callsign
but no locator, as well as for callsign-tagged messages with reports or acknowledgments.
If you agree with the sentiments I have expressed here, please help to spread the word—and lead others by your own example! When you are QRV on the moon, call CQ somewherein the sub-bands listed in Table 1, starting near the center and working outward as QRM
requires. Post a CQ notice on the logger, if you wish, encouraging others to come and ﬁnd
you . . . and then wait for the special pleasant surprise when a new “initial” or an old friend
unexpectedly responds to your call. Better still, when activity levels are suﬃcient, forgetthe logger and just call CQ! Practice random operating so that you can do it easily duringcontests, without external aids. Self-spotting and other real-time liaison are forbidden in
many contests, including the European EME Contest sponsored by DUBUS and REF.

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