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SMALL STATION EME ON 70 AND 23 CM USING JT44

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.)

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SMALL STATION EME ON 70 AND 23 CM USING JT44

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

  2. 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.)

  3. WHY WORK MOONBOUNCE 70 & 23CM EME • IT IS EXCITING! • 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. • WAY TO INCREASE YOUR GRID SQUARE AND STATE COUNT. K2UYH

  4. A BIG STATION IS NOT NEEDED! OH3MCK • MY 1ST JT44 CONTACT WAS ON 23 CM WITH OH3MCK. • OH3MCK WAS USING 2 X 25 dBi YAGIES (LINEAR POL.) AND 40 W.

  5. 2ND 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!

  6. 1ST JT44 ON 70 CM WITH ES8X 144 MHz • EUR. VHF FIELD DAY STATION ON KIHNU ISLAND (KO18xc). • 4 x 12 EL YAGIS (WITH ELEV.) AND 300 W PA. 432 MHz

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

  8. 1ST JT44 ON 70 CM WITH ES8X 144 MHz • EUR. VHF FIELD DAY STATION ON KIHNU ISLAND (KO18xc). • 4 x 12 EL YAGIS (WITH ELEV.) AND 300 W PA. 432 MHz

  9. 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

  10. EME PRACTICE • EME OPERATED USING CONVENTIONAL (CW & SSB) OR DIGITAL MODES • SOME STATIONS ARE EXPERIMENTING WITH DIGITAL MODES AS PUA43 THAT PROVIDE MANY DB ADANTAGE, 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 STNADARDS.

  11. 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!

  12. JT44 BASICS - RX AT THE END OF THE RECEPTION PERIOD JT44: • SEARCHES FOR TIME SYNC (SYNC PATTERN) 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.

  13. 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.

  14. VE7BBG’S SIGNALCOR RUNS A 7.5’ DISH AND 120W AT THE FEED TIME SYNC – FREQ –- TIME AMP -

  15. 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.

  16. STATION REQUIREMENTS IT DEPEND ON HOW BIG THE STATION IS ON THE OTHER SIDE? • 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!

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

  18. 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)

  19. OTHER SPECIAL REQUIREMENTS • FREQUENCY ACCURACY AND STABILITY *** WANT TO BE WITH IN +/- 600 Hz. (No problem on 144 MHz, but on 1296 – Can tune?) *** FREQ DRIFT < FEW Hz IN 30 SECS. *** I USE 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)

  20. 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 <http://www.thinkman.com/dimension4/>. *** CAN ALSO USE GPS STANDARD. • MUST BE ABLE TO TRACK THE MOON *** JT44 HAS BUILT IN TRACKING. (DL3OCH has GPS & digital radio clock)

  21. 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 MUST UNDERSTANDING HOW TO USE JT44 FULLY (EXCLUDE/INCLUDE, CLEAR, FOLD, FREEZE, CLIP, ETC.) • FOR SKEDS CHECK INTO K1RQG’S 20 M NET (14.345 MHz 1600Z SAT & SUN) AND READ 70 CM & UP EME NEWSLETTER <http://www.nitehawk.com/rasmit/em70cm.html> .

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