AERONAUTICAL FIXED TELECOMMUNICATIONS NETWORK AND OTHER WONDERS OF THE HF RTTY WORLD Ever peruse the RTTY column in a SWL magazine or see a file on a SWL BBS that read something like this: 13737.0 5YD Nairobi, Kenya 50/425 Coded WX...? And when you tuned it in it looked like jibberish or a bunch of numbers and you weren't sure that you had solid copy on anything but static ? Well, here is a chance to learn a little about an interesting but seldom discussed aspect of SWL-ing: Aircraft movement and meteorological messages. For starters you'll need a Shortwave receiver that is frequency stable and a RTTY decoder. Perhaps a software terminal program to link your computer to your decoder. Try tuning in one of the following frequencies: 13737.0 5YD 50/425 13996.5 STK 50/425 14600.0 CAK 50/850 The first station is in Nairobi, Kenya and usually runs a string of RYRY's for a half hour or so around 0000 UTC. If you tune in while there is no traffic being passed you will find the MARK carrier signal to zero in on and occassionally, atleast every 20 minutes, there will be sent a "channel message": ZCZC KSA042 150220 CH DE 5YD NNNN. This type of message has two purposes. One it keeps the channel occupied and two the message sequence number allows the receiving operator a tally of all messages sent that date. The message reads: ZCZC This is the beginning of a message KSA Channel (K) Kenya to (S) Sudan (A) The (A) denotes the only channel. 042 Message number 42 sent this date. 150220 Date and time of message origination CH This is a channel message DE 5YD From station 5YD NNNN End of message. Messages with other letters in place of CH have the following meanings: DD, high priority; FF, flight safety (departure or position); GG, flight safety (arrival);KK, general messages; and SS,dealing with distress. I chose the two stations for this brief because they transmit to each other. 5YD in Kenya identifies its channel as KSA and STK in Sudan uses SKA. A service message is one in which the communicators use to handle the business of communicating. i.e. ZCZC KSA050 150227 FF HSSSYFYX 150227 HKNAYFYX SVC QTA RPT SKA036 NNNN. The following may help you understand. FF Flight Safety related HSSSYFYX Khartoum-Fixed station-Military HKNAYFYX Nairobi-Fixed station-Military SVC A service message QTA Cancel telegram number.. RPT Report SKA036 Sudan to Kenya channel message 036 Location indicators are the hardest part to read. Any that begin with..H.. are Eastern Africa. HA is Ethiopa; HB Burundi HC, Somalia, etc. Those that begin with .K.. denote the USA. S for South America; L for Southern European countries. The second two letters identify the specific airfield/facility. Some American ones you will recognise: KLAX, Los Angeles; KSFO, San Francisco; KJFK, John F. Kennedy, NY. Those of you already familiar with meterological stations might recognise as old friends: KAWN, the USAF Automatic Digital Weather Switch at Carswell AFB, Tx. or KGWC, USAF Gobal Weather Center, Offutt AFB, Omaha, Ne. More of these two later. Now lets try a simple message and see if we get its meaning without too much book searching or head scratching. The line of code reads: TAF FIMP 0207 09010KT 9999 3CU020 2SC050 TEMPO 8000 80RASH 5CU015. TAF Aerodrome Forecast FIMP F..Southern Africa IMP..Plaisance,Muritius. 0207 Time of observation UTC 09010KT Wind is from 090 (East) at 10 knots. 9999 Visibility is greater than 10 kilometers. 3CU020 Amount of Cumulus cloud cover and base height. 2SC050 Amount of Stratocumulus clouds and height. TEMPO Temporary change noted/expected. 8000 Visibility to drop to 8 km horizontal. 80RASH Significate weather forecast. Rain showers. 5CU015 With increased and lowering CU cloud cover. As you can see there is a change in the weather coming. Next we will lightly touch on some other types of messages. There is the NOTAM, a message usually to warn of some problem i.e. closed runways, NavAids out or down for service, etc. The DEP which is a departure message advising the next airfield and others who, what, when and where. The ARR message announcing the arrival of an aircraft. The information within the brackets on DEP and ARR messages is for use by Air Traffic Control computers. Now let's turn our attention to the big picture; the gobal picture. Try tuning in one of these: KAWN 3230.0, 6903.0, 19325.0 50/850N CFH 6330.0 75/776R KGWC 6902.3 75/850N JMG4 14880.0 50/850N Note: Freqs, baud & shift 6VU73 13665.0 50/792N may be different. If your RTTY decoder has the UnShiftOnSpace (USOS) feature try experimenting with it on and off during reception of any message that has lots of numbers in it. Messages with the heading TTAA (upper level pressure,temperature,humidity,etc.) are all numbers. Almost continously KAWN and CFH are sending routine aviation reports labeled SA. Typically they look like this: GFA SA 1555 40 SCT 120 SCT 250 SCT 45 181/52/36/ 0000/CU ALQDS= GFA Read KGFA Malstrom AFB, Great Falls, Mt SA Routine Aviation Report 1555 Time of observation UTC 40 SCT Base of lowest clouds 4000 feet. Scattered. 120 SCT Base of middle clouds 12,000. Scattered. 250 SCT Base of upper clouds 25,000. Scattered. 45 Wind speed. 181 Wind direction. From the South. 52 Temperature. 36 Dew point temperature. 0000 Pressure in hPa. CU ALQDS Cumulus clouds all quadrants. = Separation signal. US meteological stations routinely omit the K on location indicators while Canadian stations omit the leading letter C. Station that are part of the global weather gathering service like JMG4 Tokyo transmit data from other countries. These message have AAXX in the heading (surface observation land station) and use a five digit station index number. 47671 is Tokyo International Airport. Anything from 50000 to 59999 is mainland China. 20000 thru 39999 includes all the Russias Words like TEMPO indicate temporary changes; GRADU gradual changes; NOSIG no significant weather and SKC sky clear. We have only scratched the surface. For some of you thats more than enough. For others who will want to know more I recommend: AIR AND METEO CODE MANUAL Tenth edition. 1988 Compiled by Joerg Klingenfuss. $19.95 plus $1.00 S&H from Universal Shortwave Radio 1280 Aida Dr. Reynoldsberg, OH 43068. Two other books I recommend are: CONFIDENTIAL FREQUENCY LIST Seventh edition. 1988 Compiled by Geoff Halligey $19.95 Gilfer Shortwave 52 Park Ave. Park Ridge, NJ 07656 Phone(201) 391-7887 and GUIDE TO UTILITY STATIONS Seventh Edition. 1988 $26.95 plus $1.00 S&H from Universal Shortwave Radio above. Supplements due out April and August. Eight edition is due out Dec. 1989 Submitted by Torkel Clark, N6KKA, 76057,1717. Downloaded From P-80 Systems 304-744-2253