SMALL STATION EME ON 70 AND 23 CM USING JT44 BY AL, K2UYH

OBJECTIVES  GET YOU INTERESTED IN WORKING EME. (Most hams still believe exotic equipment, huge antennas, and very high power are needed to work EME.)  SHOW THAT YOU CAN ENJOY THE THRILL OF MOONBOUNCE WITH A MODEST SETUP. (Basically the equipment you already have.)  INCREASE EME ON 432 AND 1296 MHz. (There is already a lot of small station EME on 6 & 2 m.)

WHY WORK MOONBOUNCE  IT IS EXCITING!  THE MOST FUN IN HAM RADIO IS MAKING RARE, UNUSUAL, OR DIFFICULT CONTACTS.  EME ALLOWS YOU TO WORK WORLDWIDE DX ON ANY BAND - 6 M UP.  A WAY TO INCREASE YOUR GRID SQUARES, STATES & COUNTRYS. K2UYH 70 & 23CM EME

A BIG STATION IS NOT NEEDED!  MY 1 ST JT44 CONTACT WAS ON 23 CM WITH OH3MCK.  OH3MCK WAS USING 2 X 22 dBi YAGIS (LINEAR POL.) AND 40 W. OH3MCK

2 ND JT44 QSO WITH OH1FF/p  OH FIELD DAY STATION  ALSO ON 23 CM  USING A 1.8 M DISH (CIR. POL?) AND 50 W  WE COULD HAVE QSO’D VIA CW, BUT JT44 DEFINITELY HELPED!

1 ST JT44 ON 70 CM WITH ES8X  EUR. VHF FIELD DAY STATION ON KIHNU ISLAND (KO18xc).  4 x 12 EL YAGIS (WITH ELEV.) AND 300 W PA. 144 MHz 432 MHz

KIHNU IS A SMALL ISLAND ABOUT 40 KM OFF THE COAST OF ESTONIA IN THE GULF OF RIGA, BETWEEN ESTONIA AND LATVIA. (IN ESTONIA)

1 ST JT44 ON 70 CM WITH ES8X  EUR. VHF FIELD DAY STATION ON KIHNU ISLAND (KO18xc).  4 x 12 EL YAGIS (WITH ELEV.) AND 300 W PA. 144 MHz 432 MHz

K2TXB OPERATES JT44 ON 2 m  RUSS USES 2 X KLM 16 LBX YAGIS ON A POLAR MOUNT AND A KW.  WORKED 42 STATIONS IN 15 COUNTRIES AND 15 STATES

EME PRACTICE  EME OPERATED USING CONVENTIONAL (CW & SSB) OR DIGITAL MODES  SOME STATIONS ARE EXPERIMENTING WITH DIGITAL MODES AS PUA43 THAT PROVIDE MANY DB ADVANTAGE, BUT REQUIRES SPECIAL EQUIPMENT AND TRADES TIME AND PRECISE FREQUENCY FOR SIGNAL LEVEL.  MOST DIGITAL EME IS WITH JT44.  JT44 USES STANDARD EQUIPMENT, WORKS IN VIRTUALLY REAL TIME AND HAS RELAXED FREQUENCY STANDARDS.

JT44 BASICS -TX  EACH TRANSMISSION IS 30 SECONDS LONG AND CONSISTS OF MESSAGE AND SYNC INFORMATION.  THE MESSAGE IS 22 CHARACTERS LONG AND REPEATED 3 TIMES.  THE SYNC IS INTERSPERSED WITH THE MESSAGE AND SENT ABOUT HALF THE TIME.  A UNIQUE FREQUENCY IS ASSIGNED TO LETTERS, NUMERALS AND PUNCTUATION CHARACTERS (43 TONES) + SYNC = 44!

JT44 BASICS - RX AT THE END OF THE RECEPTION PERIOD JT44:  SEARCHES FOR TIME SYNC (SYNC PATTEREN) OVER –4 TO 1 SECOND DELAY PERIOD.  SEARCHES FOR FREQ OFFSET (+/- 600 Hz).  DETERMINES AND DISPLAYS MESSAGE.  AVERAGES CHARACTERS IN EACH TIME SLOT OF THE 22 CHARACTER MESSAGE.

AVERAGING  WHEN A SIGNAL IS STRONG CAN GET FULL COPY IN A SINGLE SEQUENCE – (QSO in < 2.5 min!)  OFTEN SIGNALS ARE WEAK AND THE MESSAGE GARBLED – (This is where JT44’s averaging pays off.)  IF THE SAME MESSAGE IS SENT EACH SEQUENCE, JT44 WILL AVERAGE THE RESULTS OF ALL PERIODS.  THE MESSAGE WILL CORRECT ITSELF WITH EACH SUCCESSIVE PERIOD.

VE7BBG’S SIGNAL COR RUNS A 7.5’ DISH AND 120W AT THE FEED TIME SYNC – FREQ –- TIME AMP -

ECHO MODE – WANT TO TRY EVEN IF DON’T USE JT44 FOR EME!  LET’S YOU EVALUATE EME SYSTEM CAPABILITY.  NOT GOOD FOR COMMUNICATIONS.  ON 70 CM COPIED ECHOES WITH 200 W ON HORZ WITH TROPO STATION.

STATION REQUIREMENTS IT DEPENDS ON HOW BIG THE STATION ON THE OTHER SIDE IS?  ON 70 CM – SINGLE LONG YAGI AND > 100 W. *** WANT TO ELEVATE (REALLY A MUST)! *** PREAMP AT THE ANTENNA ( AND PA AT ANT ). *** POLARIZATION ROTATION?  ON 23 CM – SINGLE LONG LOOP YAGI OR 5’ DISH WITH CIRCULAR FEED AND > 50 W. *** CIRCULAR POL GAIN + 3 dB!

PORTABLE EME – DL3OCH STYLE  BODO USES IC-706, HB TRANSVERTER WITH 100 W AND A 59 EL YAGI (5 m long & 18.7 dB d )FROM HIS CAR.  BESIDES DL, HE HAS OPERATED FROM 3A AND HB0.

YOU NEED A COMPUTER AND SOUND CARD  SHOULD RUN 32 BIT VERSIONS OF THE WINDOWS OPERATING SYSTEM AND BE FAST ENOUGH TO HANDLE JT44 AND SEVERAL OTHER TASKS.  A 300 MHz PENTIUM OR BETTER WITH WINDOWS 98 OR PREFERABLY WINDOWS 2000 OR XP WILL BE MORE THAN SUFFICIENT.  NEED TO INTERFACE THE COMPUTER TO YOUR RIG 1) PTT FROM SERIAL PORT (VOX will work), 2) TX AUDIO FROM AUDIO OUT OF SOUND CARD, & 3) RX AUDIO TO INPUT OF SOUND CARD. (DL3OCH uses Acer laptop – 650 MHz Celeron)

OTHER SPECIAL REQUIREMENTS  FREQUENCY ACCURACY AND STABILITY *** WANTS TO BE WITHIN +/- 600 Hz. (No problem on 144 MHz, but on 1296 – Can tune?) *** FREQ DRIFT < FEW Hz IN 30 SECS. *** I USE A GPS STANDARD.  DOPPLAR SHIFT CORRECTION *** NOT IMPORTANT ON 144, BUT SIGNIFICANT ON 432 (can be > 1 kHz) AND 1296 (can be > 3 kHz). *** MUTUAL DOPPLAR CAN BE VERY DIFFERENT FROM LOCAL ECHO SHIFT! *** JT44 HAS BUILT IN CORRECTION. (DL3OCH – nothing special)

OTHER REQUIREMENTS CONT’D  MUST KNOW TIME TO ~ 1 SECOND. *** I USE RADIO SHACK WWV CLOCK AND SET MY COMPUTER BEFORE SKEDS *** SOFTWARE IS AVAILABLE TO AUTOMATICALLY TO UPDATE YOUR CLOCK VIA THE INTERNET. *** CAN ALSO USE GPS STANDARD.  MUST BE ABLE TO TRACK THE MOON *** JT44 HAS BUILT IN TRACKING. (DL3OCH has GPS & digital radio clock)

CONCLUSION  EME WITH JT44 IS NEW AND CHALLENGING.  IT’S NOT JUST HAVING A YAGI, A100 W AND A COMPUTER!  THE COMPUTER DOES NOT DO EVERYTHING FOR YOU!  IT IS PRETTY EASY WITH A BIG STATION, BUT THERE IS STILL A LOT TO IT: ACCURATE FREQ AND TIME, MOON TRACKING, DOPPLAR, POLARIZATION (ON 432).  WITH A WEAK STATION, ALL THE ABOVE PLUS YOU MUST UNDERSTANDING HOW TO USE JT44 FULLY (EXCLUDE/INCLUDE, CLEAR, FOLD, FREEZE, CLIP, ETC.)  FOR SKEDS CHECK INTO K1RQG’S 20 M NET ( MHz 1600Z SAT & SUN) AND READ 70 CM & UP EME NEWSLETTER.