For RTTY I used my ICOM 746 Pro, a SignaLink USB Integrated USB Sound Card, MMTTY free Software and a Toshiba Laptop. (I have since sold all my HF equipment)
My IC 746Pro must be in LSB "D" mode. (D = Digital mode).
The SignaLink only can use AFSK and not FSK. It works fine once I figured it out.
Why do you see RYRYRY in RTTY?
In the days of mechanical RTTY, the "R" and the "Y" letters exercized all five of the "Bits" of the Five Bit Baudot code. Clear "RYRYRYRYS" meant the machinery was timed and running correctly.
"THE QUICK BROWN FOX JUMPS OVER THE LAZY DOG" line in a test transmission uses every letter of the alphabert at least once.
Neither "RYRYRY" or "THE QUICK BROWN FOX" are really necessary. However, they are still uded for tradition, and because they still serve a similar purpose.
So, the areas normally associated with RTTY are as follows (frequencies in kHz)... Normally where the most activity is found. You could use RTTY anywhere as long as it didn't interfere with emergency or prioity traffic.
160M - 1800 to 1820 (although use of RTTY is rare on this band and you may find activity higher up in the 'all modes' area if there is any activity)
80M - 3580 to 3650
40M - 7080 to 7100 (differs in USA and Japan)
30M - 10110 to 10150
20M - 14080 to 14099
15M - 21080 to 21100
10M - 28080 to 28100
YOUR FIRST RTTY QSO
Ok, you’ve learned a lot and you’re ready to get on the air! For your first time on RTTY, try the 20 meter band. 20 has the lion’s share of RTTY activity and you can usually find someone, day or night. Try calling CQ between 14080 and 14087 kHz. A typical RTTY CQ would go like this: CQ CQ CQ CQ CQ CQ DE Your Call Sign, Your Call Sign, Your Call Sign PSE K
Practically all RTTYers add the “PSE” at the end. Just a friendly touch. Some will add their name and QTH, some will add the time and date. You’ll find a lot of variety and it’s all ok – just get on the air and try it out!
If you’re familiar with CW procedures, you’ll be right at home with RTTY. RTTYers use most of the Q-signals, as well as DE, K, KN, and most of the CW abbreviations. And if you accidentally find yourself “upside down”, don’t get embarrassed – we’ve all done it! RTTYers are some of the nicest people you’ll ever meet. Things like jamming, profanity and rudeness are almost unheard of.
FSK vs AFSK
You will often hear the terms FSK and AFSK when talking about RTTY on the HF bands. FSK means Frequency Shift Keying and AFSK means Audio Frequency Shift Keying. Regardless of which method is used, the RF signal sent out over the air is identical. MARK is always the higher RF frequency and SPACE is always the lower RF frequency. If the transmitter is operating properly, the station receiving the RTTY signal can not tell any difference at all. So what is the difference? It’s the way your transmitter generates the RF signal.
With FSK, your transmitter receives a simple on-off signal which causes the carrier frequency to shift back and forth. This signal may come from a TNC (Terminal Node Controller) such as a Kantronics KAM, an AEA PK-232, HAL DXP-38 or some other, or it may come from a soundcard program via one of your computer’s com ports. FSK is simpler, easier and more foolproof than AFSK and is highly recommended if your transmitter supports FSK input. Check your owner’s manual if you’re not sure.
Since not all transmitters support FSK input, there is another method available – AFSK. AFSK can be used with any SSB transmitter. AFSK is a bit trickier to set up and use, but when it is done correctly, it works just as well as FSK and will transmit a perfect RTTY signal. Also, AFSK can do some things FSK can not, such as Automatic Frequency Control (AFC) of the transmitter. With modern transmitters, drift is not a problem and transmit AFC is generally not needed. With older tube-type equipment, it may offer some advantage.
To operate with AFSK, you put your transmitter in the SSB mode instead of FSK mode, and you put an audio signal into the microphone input (some transceivers have a rear connector for audio data input). When you transmit your TNC or soundcard will put out a pair of audio tones that cause your transmitter to send the required RF output. Sounds simple, right? Here’s the tricky part: The tones are two simple sine waves, but the frequency and amplitude of the tones is critical. Let’s say you want to transmit on 14080.00 kHz, as in the previous example. Remember that your MARK signal has to be on 14080.00 kHz and SPACE 170 Hz lower. How do you do that with AFSK? Here’s how. With your transmitter in the LSB mode (Lower Side Band), whatever frequency goes into the microphone input will be subtracted from what your dial says and be transmitted on that frequency. For example if your dial says 14080.00 kHz and you put in a 1000 Hz audio tone, your transmitter will put out an RF signal at 14079.00 kHz, exactly 1000 Hz lower than your dial. So in this case, if the 1000 Hz represented your MARK signal, you would have to set your transmitter to 14081.00 on the dial, and your MARK signal would be transmitted on 14080.00, just as you wanted. Ok so far? Now, what about SPACE? Remember, you want your SPACE signal to be transmitted 170 Hz lower, on 14079.83 kHz. What audio tone will give you 14079.83? Simple – 14081.00 minus 14079.83, or 1170 Hz. So the MARK audio frequency is 1000 Hz and SPACE is 1170 Hz.
There you have the basics of AFSK. Your TNC or soundcard generates the two audio frequencies and your transmitter converts them into two RF frequencies. For technical reasons related to harmonic generation, audio frequencies of 1000 Hz and 1170 Hz are NOT recommended. They are used in this example just to keep the math simple. The recommended audio frequencies are 2125 Hz for the MARK audio frequency and 2295 Hz for the SPACE audio frequency. Making the frequencies higher like this will reduce second harmonics while keeping the tones within the passband of your SSB transceiver.
If you’ve been paying close attention, you may have noticed the SPACE audio frequency is higher than the MARK audio frequency, just the opposite of the RF frequency. This happens because you’re using lower sideband. If you happen to forget and set your transmitter to USB instead, two things will happen. Because your MARK and SPACE are now reversed in your receiver, any RTTY signals you hear will not print correctly. All you will see is random characters that make no sense at all. The other thing is that YOUR transmissions will also be nonsense to the other guy. So just remember – always use LSB. In the real world of course, sometimes USB gets selected accidentally. Nearly all software has a means to quickly reverse the tones, either a keyboard command or an on-screen button to click. When you have a station tuned correctly but all you see is nonsense printing reverse the tones. Now you can print the other fellow and tell him he is “upside down”, as it’s called. After he reverses himself, just reverse again and you will both be back to normal.
Also, you should know that in some parts of the world, especially Europe, the standard is to use USB instead of LSB. This works fine as long as you also reverse the two audio tones. In the US, nearly all equipment defaults to LSB. If you prefer to use USB, be sure your tones are reversed all the time.
The really critical part about AFSK is the amplitude of the signal fed into the microphone connector (or rear panel connector), together with the microphone gain setting. You must NOT overdrive your transmitter or spurious signals will be transmitted. In general, keep the audio drive low enough that your transmitter does not generate any ALC voltage. Never try to drive your transmitter to maximum output. Around 80 to 90 percent of maximum is about right. Consult your owner’s manual for more information on how to do this. If you ever hear a station at two or more frequencies at the same time, the cause is almost always overdrive. None of this applies to FSK, of course. With FSK, you can run full power and not worry about overdrive.