THE DIGITAL MODES
THIS SECTION UNDER CONSTRUCTION
RTTY - RADIO TELETYPE
PSK - PHASE SHIFT KEYING SSTV - SLOW SCAN TELEVISION
AMATEUR RADIO SATELLITES
THIS SECTION UNDER CONSTRUCTION
THIS SECTION UNDER CONSTRUCTION
RTTY - RADIO TELETYPE
PSK - PHASE SHIFT KEYING SSTV - SLOW SCAN TELEVISION
THIS SECTION UNDER CONSTRUCTION
WITH THE USE OF A SOUND CARD EQUIPPED PC AND THE EXCELLENT SOFTWARE AVAILABLE TODAY, IT IS A RELATIVELY EASY JOB TO RECEIVE AN APT (AUTOMATIC PICTURE TAKING) IMAGE FROM VARIOUS AMERICAN AND RUSSIAN WEATHER SATELLITES OF WHICH CURRENTLY THERE ARE FOUR NOAA SATELLITES; NOAA 12, NOAA 14, NOAA 15, NOAA 17 AND TWO METEOR SATELLITES; METEOR 2-21 AND METEOR 3-5 AVAILABLE OVER THE U. S. FOR RECEIVING APT. NOAA 12 IS CURRENTLY TURNED OFF BECAUSE OF INTERFERENCE WITH NOAA 15 BUT IS SCHEDULED TO BE TURNED BACK ON IN AUGUST 2002. BOTH METEOR 2-21 AND METEOR 3-5 OPERATE SOME OF THE TIME BUT ARE NOT PREDICTABLE, JUST HAVE TO LISTEN FOR THEM.
THERE ARE TWO TYPES OF WEATHER SATELLITES OF INTEREST TO THE AMATEUR, POLAR ORBITING SATELLITES THAT CIRCLE THE EARTH IN APPROXIMATELY 101 MINUTES AND THE GEOSTATIONARY SATELLITES THAT APPEAR AT A FIXED LOCATIONS IN THE SKY. THE POLAR ORBITING SATELLITES (LEO) ARE THE ONE WE WILL BE EXPLORING HERE. THESE SATELLITES TRAVEL IN A NORTH-SOUTH ORBIT WITH A CONSISTENT ANGLE TO THE SUN AND ARE THEREFORE CONSIDERED TO BE IN A SUN-SYNCHRONOUS ORBIT, THEREBY PASSING OVER A PARTICULAR PART OF THE WORLD AT NEARLY THE SAME TIME EACH DAY AS THE EARTH ROTATES. THE NOAA SATELLITES ARE TYPICALLY ABOUT 500 MILES OUT IN SPACE AND ARE EQUIPPED WITH BOTH VISIBLE AND INFRARED SENSORS, AND CREATE TWO SIDE BY SIDE APT LOW RESOLUTION IMAGES SIMULTANEOUSLY. BY USING BOTH THE VISUAL AND INFRARED TRANSMISSIONS THIS ALLOWS FOR VIEWING BOTH DAY AND NIGHT PASSES. THERE ARE UP TO FOUR DAY AND NIGHT PASSES, NORTH-SOUTH DIRECTION IN THE MORNING PASSES AND SOUTH-NORTH PASSES IN THE AFTERNOON. THE METEOR SATELLITES ARE 600- 800 MILES OUT IN SPACE AND HAVE ONLY VISUAL CAPABILITIES AND, THEREFORE, TRANSMIT ONLY A SINGLE DAYTIME IMAGE.THERE ARE A TOTAL OF TWO PASSES PER DAY. WHEN OUT OF THE VIEW OF THE SUN, THE METEOR SATELLITES TRANSMITTER IS AUTOMATICALLY TURNED OFF. THE NOAA SATELLITES SCAN AN AREA APPROXIMATELY 1700 MILES WIDE AND SLIGHTLY MORE ON THE METEOR SATELLITES. THE PASSES WILL LAST 10 TO 15 MINUTES FOR THE NOAA SATELLITES AND UP TO 20 MINUTES ON THE METEOR SATELLITES, ALLOWING FOR PICTURE COVERAGE FROM MY LOCATION (83 DEGREES LONGITUDE) WITH AN OVERHEAD PASS FROM THE UPPER HUDSON BAY TO THE CENTRAL AMERICAS.
SEE NOAA SATELLITES FOR MORE DETAILED INFORMATION.
YOU WILL NEED A VHF RECEIVER CAPABLE OF RECEIVING THE 137 MHZ FM SATELLITE FREQUENCIES. A LOT OF THE SCANNING RADIO'S DO NOT HAVE THE NECESSARY I.F.BANDWIDTH OF ABOUT 50 KHZ., REVIEW THE RECEIVER SPECIFICATION THAT PERTAIN TO BANDWIDTH. HAVING A RECEIVER WITH TO WIDE OF A BANDWIDTH WILL CAUSE A REDUCTION IN THE SIGNAL LEVEL, ALONG WITH NOISE AND VERY LIKELY PROBLEMS WITH ACARS TRANSMISSION IF YOU LIVE IN AN AREA WITH A LOT OF AIR TRAFFIC.
THERE ARE SEVERAL RECEIVERS ON THE MARKET THAT WILL FILL THE BILL RATHER NICELY. ONE BEING HAMTRONICS R139 WEATHER FAX RECEIVER, BUILT EXCLUSIVELY FOR WEFAX RECEPTION AND ANOTHER IS THE PCR-1000, I USE THE PCR-1000 WITH THIRD PARTY SOFTWARE. TALKPCR
THERE ARE A COUPLE OF FINE FULL FEATURE PROGRAMS AVAILABLE THAT DOES A GREAT JOB. ONE IS DAVE RANSOM'S STSPLUS, A DOS APPLICATION AND ANOTHER ONE IS DAVID TAYLOR'S WXTRACK, A WINDOW'S APPLICATION. I USE THEM BOTH.
IT IS IMPERATIVE THAT YOUR COMPUTER CLOCK KEEP ACCURATE TIME IN ORDER FOR YOUR TRACKING PROGRAM TO DISPLAY THE THE PASSES ACCURATELY. MOST COMPUTERS THAT I HAVE USED, HAS SHOWN THAT THE COMPUTER CLOCK COULD BE OFF SEVERAL SECONDS A DAY AND THIS ERROR IS ACCUMULATIVE AND CAN LEAD TO A LARGE ERROR OVER TIME.(SOME OLDER COMPUTER CLOCKS COULD SHOW EVEN LARGER ERRORS). IF YOU ARE RECORDING THE PASSES AT A PREDETERMINED TIME, TO BE PLAYED LATER, WITH INACCURATE TIME YOU MAY MISS A PART OF THE PASS. CHECK OUT THIS PROGRAM TO KEEP YOUR COMPUTER CLOCK ACCURATE, SET COMPUTER TIME, FROM THE NATIONAL INSTITUTE OF STANDARDS AND TECHNOLOGY (NIST).
THE RECEIVER'S AUDIO IS FED INTO THE PC SOUND CARD WHICH DOES THE DEMODULATING BY USING APPROPRIATE SOFTWARE. THERE IS AN EXCELLENT FREE WARE PROGRAM THAT HAS BEEN AVAILABLE FOR SEVERAL YEARS, WXSAT WRITTEN BY CHRISTIAN BOCK THAT DOES AN ADMIRABLE JOB OF DECODING THE SATELLITES.SEE THE BEGINNER'S GUIDE TO WXSAT PROGRAM BY LES HAMILTON FOR SOME GREAT TIPS. WITH THE WXSAT PROGRAM IT CAN ACTUALLY COMBINE THE TWO IMAGES, VISIBLE AND INFRARED TOGETHER, TO OBTAIN A COMPOSITE FALSE COLOR PICTURE WITH BETTER RESULTS THAN BE COULD PRODUCE BY THE SEPARATE IMAGES.THE NOAA 17 IMAGE AT THE BEGINNING OF THIS SECTION WAS DECODED WITH WXSAT. THERE IS NOT A GREAT DEAL OF EDITING OF THE FINAL IMAGE IN TH WXSAT PROGRAM, BUT THERE IS ONE USEFUL ITEM, YOU ARE ABLE TO EDIT OUT LINES IN THE IMAGE SUCH AS A BURST FROM ACARS TRANSMISSION, ETC. FURTHER EDITING CAN BE DONE WITH ABOUT ANY OF THE IMAGE PROCESSING PROGRAMS AVAILABLE, AND THERE ARE MANY TO CHOOSE FROM. ANOTHER PROGRAM CALLED WXTOIMG , FROM ABSTRACT TECHNOLOGIES NEW ZEALAND LIMITED, A FULL FEATURED PROGRAM THAT DOES IT'S OWN DECODING AND HAS AN EXCELLENT MAP OVERLAY FEATURE. ALSO ANOTHER EXCELLENT PROGRAM CALLED SATSIGNAL BY DAVID TAYLOR IS AVAILABLE BUT REQUIRES THE SOUND FILE CREATED BY WXSAT. YOU CAN CHECK IT OUT AT THE SATSIGNAL PAGE. DAVID HAS AN EXCELLENT WEB SITE WITH LOTS OF SATELLITE RELATED PROGRAMS AND KEEPS HIS PROGRAMS AND WEB SITE UPDATED REGULARLY. THIS IS BY NO MEANS ALL OF THE DECODING PROGRAMS AVAILABLE, BUT THE ONES I HAVE TRIED.
I HAVE TRIED SEVERAL DIFFERENT ANTENNAS TO RECEIVE THE SATELLITES (NOAA SATELLITES TRANSMITS A 5 WATT RIGHT HAND CIRCULARLY POLARIZED SIGNAL) DIPOLES, GROUND PLANE, TURN STILE, LINDENBLAD ANTENNA AND TWO VERSIONS OF THE QUADRIFILAR HELIX, QFH ANTENNA, TALL NARROW QHF. THE USE OF A OMINIDIRECTIONAL ANTENNA NEGATES THE PROBLEMS WITH ROTATABLE DIRECTIONAL ANTENNAS HAVING TO DEAL WITH AZIMUTH AND ELEVATION FACTORS. THE QFH ANTENNA IS RELATIVELY EASY TO CONSTRUCT AND REQUIRES NO ADJUSTMENTS. PAY CLOSE ATTENTION TO THE DIRECTION THE HELIX IS WOUND OTHERWISE YOU WILL WIND UP WITH THE WRONG POLARIZATION AND THERE IS NO WAY TO REVERSE THIS SHORT OF REWINDING THE HELIX. USE GOOD QUALITY COAX AND FITTINGS. I USE THE HAMTRONICS PREAMP , BUT WITH REASONABLE HEIGHT, SHORT FEED LINE LENGTH AND GOOD CONNECTORS YOU MAY NOT NEED A PREAMP. THE LONG VERSION QFH GIVES NEAR HORIZON TO HORIZON COVERAGE WITH ALMOST A CONSTANT SIGNAL ACROSS THE ENTIRE PASS. THE SHORTER QFH ANTENNA GIVES A STRONGER SIGNAL AT MAXIMUM ELEVATION WITH REDUCED SIGNAL ON THE HORIZON, STILL THIS VERSION WILL GIVE YOU GOOD COVERAGE OVER A LARGE PART OF THE SATELLITE PASS. DON'T WORRY IF YOU ARE BOTHERED WITH A LOT OF TREES, AS I AM. THE QFH ANTENNA I AM USING IS ONLY ABOUT 30 FEET OFF THE GROUND AND PROPERTY IS INUNDATED WITH TREES.
THE NATIONAL WEATHER SERVICE, A PART OF NOAA, BROADCAST INFORMATION PRIMARILY FOR THE MARINER. THESE BROADCAST FROM THE USCG HF RADIOFAX SYSTEM CONTAINS SEAS WEATHER MAPS, SEA SURFACE TEMPERATURE MAPS, AND LATE IMAGES FROM THE GOES WEATHER SATELLITE FROM BOSTON, MASS; NEW ORLEANS LOUISIANA; POINT REYES, CALIFORNIA; KODIAK, ALASKA; AND HONOLULU, HAWAII. THESE TRANSMISSIONS CAN BE RECEIVED ON ANY HF RECEIVER CAPABLE OF RECEIVING THE FREQUENCIES AND BE CAPABLE OF RECEIVING SSB/USB MODE. THE WEATHER FACSIMILE PICTURES ARE TRANSMITTED USING FM MODULATION AND A DEVIATION OF 800 HZ SHIFT AND CAN EASILY BE DEMODULATED WITH A NORMAL SSB RECEIVER.THE FREQUENCY IS TYPICALLY 1.9 KHZ. BELOW THE STATIONS ASSIGNED FREQUENCY. THE SAME EQUIPMENT USED TO DISPLAY AND DECODE THE WEATHER SATELLITES (AS DESCRIBED ABOVE) CAN BE USED TO DISPLAY THE HF WEFAX IMAGES. THERE IS A SELECTION IN THE WXSAT PROGRAM PARAMETERS MENU ENTITLED FM-120 THAT WILL DECODE THESE FAX IMAGES.
THE BEACON NETWORK IS A WORLD WIDE NETWORK, CONSISTING OF FIVE HF RADIO BEACONS THAT WILL AID THE AMATEUR IN HIS QUEST FOR THE BEST BAND OPENINGS FOR 20 THRU 10 METER BANDS. CHECK OUT THE ARTICLES AND SOFTWARE LINKS BELOW.
ACARS- AIRCRAFT COMMUNICATIONS ADDRESSING AND REPORTING SYSTEM - IS A DIGITAL MODE, DATA LINK SYSTEM, FOR TRANSMISSION OF INFORMATION TO AND FROM AN AIRCRAFT AND ITS COMPANY. TRANSMITTING IN THE VHF AIRCRAFT BANDS, COMMUNICATIONS CONSISTS, AMONG OTHER THINGS, ARRIVAL AND DEPARTURE INFORMATION, ENGINE OPERATING DATA, FUEL ON BOARD,LOCATION, GATE ASSIGNMENTS ETC. THIS IS ALL DONE THROUGH ARINC - AERONAUTICAL RADIO, INC, WHERE TRAFFIC IS PROCESSED THROUGH ARINC COMPUTER SYSTEMS BY THE COMPANIES USING THIS SYSTEM. YOU CAN EASILY RECEIVE THESE TRANSMISSIONS WITH A DECODING PROGRAM CALLED WACARS,AN ANTENNA, A RECEIVER CAPABLE OF RECEIVING THE AM SIGNAL IN THE VHF AIRCRAFT BANDS AND A SOUND CARD EQUIPPED COMPUTER. I DO NOT USE A DEDICATED ANTENNA FOR THE RECEPTION OF ACARS, IN FACT I USE MY QFH ANTENNA THAT I USE FOR SATELLITE RECEPTION. A SIMPLE GROUND PLANE ANTENNA WOULD BE SUFFICIENT FOR GOOD RECEPTION. IN MY LOCATION THERE ARE MANY, MANY AIRCRAFT IN RANGE OF RECEPTION AT ANY GIVEN TIME.
THE WACARS PROGRAM WILL DECODE THE TRANSMISSIONS AND DISPLAY A RAW DATA LOG, A MESSAGE LOG, AIRCRAFT CONTACTED LOG AND A FLIGHTS CONTACTED LOG. ALL LOGS WITH THE EXCEPTION OF THE RAW DATA LOG CAN BE SAVED FOR LATER REVIEW IF DESIRED. IT WILL ALSO DISPLAY A MAP SHOWING THE LOCATION OF THE AIRCRAFT WHENEVER THE AIRCRAFT TRANSMITS IT LONGITUDE AND LATITUDE. THE TABLE BELOW LIST SOME OF THE MORE COMMON FREQUENCIES FOR ACARS.
THE FOLLOWING IS A LIST OF FREQUENCIES USED BY ACARS IN THE UNITED STATES AND CANADA TO TRANSMIT DATA TO AND FROM THE AIRCRAFT.
