ed for both VHF AFSK and HF FSK operation. Radioteletype in Australia Most HF RTTY amateur stations group also meets in Perth. use audio tones with an SSB transmitter. In Australia, radioteletype is Although "standard" audio tones for VHF transmitted on HF and VHF bands. In Australia there are no restrictions amateur operation have long been The most commonly used shift on the codes that may be transmitted. 2125Hz for mark and 2975Hz for space frequency is 170Hz, with the mark Amateur radioteletype enthusiasts (850Hz shift), limited audio frequency frequency being 2125Hz. Both low may use "any recognised code" at a shift frequency of not more than response of HF SSB transmitters and and high tones are used on HF, while

I at 45.5 is receivers have recently given rise to a high tones are used on VHF as in the 850Hz. second set of "standard" tones at lower US. most commonly used although some frequencies ("Low -tones"). RTTY transmissions can be copied experimenters are transmitting in ASCII. On the HF bands, ASCII How about high- vs low -tones? on 3.5MHz, 7.045, 14.090, 21.090 and 28.090MHz. The standard transmissions are very prone to noise, were Historically, demodulator tones international frequency is 3.54MHz. and experiments are being carried out mark set to 2125Hz for and 2975Hz for On VHF the frequency most used is with error -correcting codes. reception When space of 850Hz shift. 146.6MHz. Two repeaters in NSW Radioteletype transmissions from transmitter stability improved, 170Hz operate with output frequencies of the USA and Europe can be received shift was used and space frequency the 146.625 and 146.675MHz, and a throughout Australia. two notable changed to 2295Hz (mark remained at Brisbane repeater works at stations are W1OW, the American 2125Hz). These three tones were, and 146.625MHz. Radio Relay League station, and still are, a standard for US amateur RTTY. ANARTS, the Australian National GB2ATG, the British Amateur However, in the early 1960's, virtually all Society, Teletype Group. GB2ATG broadcasts commercially available transmitters and has been active now for almost four daily at 073OUTC on 14.090MHz, receivers became filter -type SSB equip- years, and has a membership of over while W1OW transmits four times a ment with pass limited audio -band to 600. The Society provides information day, at 0100, 0400, 1500 and speech frequencies, sometimes as nar- and technical assistance to members, 22000TC on 14.095, 21.095 and row as 2.1kHz (300 to 2400Hz). transmits RTTY news and views, and 28.095MHz. Stations in Europe can Obviously, the 2974Hz (850Hz shift also makes available kits of parts for also be contacted, and some of these space) tone will not pass through a such RTTY equipment. stations operate as message and 850Hz shift these is filter with tones ANARTS news broadcasts from switching centres, storing and not possible (although the 170Hz shift is). Sydney are at 003OUTC each Sunday forwarding messages from one Therefore, either the SSB equipment on 7045kHz, 14.090, 14.095 and amateur to another. must be modified or different, lower - 146.6MHz. The news broadcast is Using a surplus Baudot teleprinter, frequency tones must be used if 850Hz repeated at 093OUTC on 3545kHz, and modulator and demodulator kits RTTY shift is desired. Both approaches 146.6 and 146.675MHz, and VHF from ANARTS, the RTTY amateur have their advantages and both are cur- can relays of the broadcast are made to be on the air for as little as $150 rently in use. The so-called "low -tone" other states. At 013OUTC on Sunday above the cost of a transceiver. standard sets mark at 1275Hz and space an RTTY DX bulletin is transmitted, and Radioteletype is particularly suited to at 1445Hz (170Hz shift) or 2125Hz according to publicity office Sid novices, who are restricted to a (850Hz shift), conforming to the Euro- Molen, ANARTS is the only station in maximum transmitter power of 30W pean IARU standard. So, there are now the world providing detailed DX PEP. Since radioteletype is a "key two sets of "standard" tones, low and information for radioteletype. down" mode, with the transmitter in high (as well as a myriad of others), all of The Society meets on the first continuous operation, most which work interchangeably on HF RT- Tuesday of every second month, at transceivers need to be de -rated to TY. However, since the actual audio the Wireless Institute Centre, 14 about 30% of their maximum power tone is transmitted for VHF AFSK opera- Atchison St, Crows Nest, NSW. The output for RTTY use. Novices thus tion, the two sets are not compatible in next meeting will be held on August 4. face much less competition from high VHF AFSK applications. Current US The postal address is PO Box 860, power broadcasts in the radioteletype amateur operation uses the high tones Crows Nest, NSW 2065. An RTTY mode. for VHF. Thus, to use a demodulator and keyer for both HF and VHF operation, it I we should be set up for high -tone operation. Who do talk to on RTTY? beginner, have the following RTTY enthusiasts run the full range of recommendations: What frequencies do I use for (1). Demodulator: Assuming you RTTY? ages and interests, but tend to be technically inclined. The typical RTTY'er already have a good transceiver and HF RTTY operation has evolved to is always modifying his station, likes to antenna, your first major RTTY purchase the 80 and 20 metre heavy'operation on talk, and usually has more ideas than you should be a good demodulator. If you with sporadic bands (CW segments) have printer paper (or display screen)! select a high -tone transceiver it will be on other HF bands. Eighty operation Some operators are good typists; most usable for either VHF or HF (170Hz shift) metre RTTY stations tend to operate bet- aren't. Recently, the home computer RTTY operation; if you are only ween 3600 and 3650kHz and 20 metre hobby has popular with interested in' HF RTTY (for shortwave between 14.075 and become quite stations RTTY people and you may find a lot of listening to press stations, for example), 14.100MHz. 170Hz shift is used almost help in debugging your programs if that's a low -tone unit may be a better choice. exclusively with mark being the higher your interest. There are also an increas- Either way, put high priority on a good radio frequency. 60wpm (45 baud) is the ing number of DX stations on RTTY. demodulator. - most popular RTTY speed, but 100wpm (2). Terminal: You can spend very little (74 is in popularity. baud) gaining How much does It cost? or a lot on the terminal. A surplus VHF RTTY operation in most areas is RTTY is like any other hobby - it can machine can often be acquired for little concentrated on two metre FM with cost as much or as little as you want it to. cash investment. However, by the time 146.700MHz being the popular If you buy used machines and build kits you figure out how it works, fix it, and operating frequency. Virtually all stations or your own designs, the total RTTY cost buy parts and manuals the total cost may are now using the "high-tones", usually can be quite low. Because most RTTY not be so low. If you do, you'd better be with 170Hz shift. As with HF RTTY, products are current loop compatible, prepared with tools, oil, and patience. 60wpm (45 baud) is most popular on you can add devices as your interests Newer machines require less work, but VHF. (and wallet) indicate. For the also cost more. ,74 26 Australia, October, 1981