K5LAD - 50+ Years of Ham Radio Memories
Volume XXXIVI Waited Long Enough and My
Diddles Have Returned
By Jim Pickett K5LAD
Search keywords: Ham RTTY, Derrick Electronics Many years ago, actually back in the late 60s and early 70s, I was active in RTTY or Radio TeleTYpe. I spent time on both FSK teletype on the low bands and AFSK teletype on the 2 meter VHF band. FSK, or Frequency Shift Keying, is done by shifting the actual frequency of the transmitted signal whereas AFSK shifts the audio frequency of the signal by feeding the shifted tones directly into the TX mike input. To complicate the definition, it is possible to generate FSK by feeding audio shifted tones into the SSB transmitters audio input, however that is not pertinent to this particular story.
There was a time, long before the days of APRS or Packet operations, in the Tulsa area when several stations used a dedicated 2 meter FM transceiver at their house, to monitor a specific frequency and a dedicated audio teletype converter hooked to an old TTY machine. The current local repeater on 146.10/.70 was originally a repeater primarily for AFSK use on 2 meters.
Most of the Teletype equipment available to the hams was that which had seen service in WWII and was nearly indestructible. Not only was it built like a battleship but some were actually built FOR a battleship. A few folks had machines, like the smaller Model 26, that came out of telephone and Western Union service but most of us used Model 15, 19, and 14s from the military and much of it was available free to us through the MARS program. MARS does not have any ties to the Area 51 area of science fiction and alien fame. MARS stands for Military Affiliate Radio Service and was a secondary program to train US amateurs in military radio procedures in case there was a need for communications during a disaster that the military was not able to fully cover. Hams spent several hours each month learning this military radio and communications protocol and in exchange for their time and efforts, they were able to receive old military electronic equipment for their own use. Some of the equipment was barely used; some had seen major usage and required some repairs before it could be used. Every so often, it was possible to get a brand new piece of equipment that the military no longer needed or used. A lot of the Teletype equipment came through these MARS sources and where a ham might never have been able to purchase something this complex, they were able to get it free and often not even need to pay for any shipping charges.
To say that they were noisy in operation would be an understatement but they were great fun to both operate and operate upon for if something went wrong with your machine, you were the usually the only one who could do the repairs. They were usually liberally oiled to keep them going and the floor under the machine often had cans in strategic places to catch the oil drips. It often looked something like the buckets placed around the house of Ma and Pa Kettle to catch raindrop drips from the holes in the roof.
The local 2 meter network system used a converter that had a relay built into it. When the converter would hear a certain tone for several seconds (through the dedicated FM transceiver), the relay would engage and apply AC power to the TTY machine. The message would be sent on the frequency and any receiver within range would, through the converter, cause the machine to print the message. When the sender had completed their message, they turned off their transmitter, the tone would go away and the relays on the listening stations would drop out and the TTY machine would go back to sleep. It was a good way to leave messages for your friends so it would be awaiting them when they came home from work or when they awakened in the morning. It was a simple and good system and worked well.
There were stories told about ham groups in other geographic areas with a system like this, particularly in the Chicago area, who would key up their transmitter and send the "turn on tone," then put in a tape sending <lf> or line feeds in a loop. Each <lf> would cause the machine to advance one line of paper from the paper roll supplying the printer section. When the others around the area came home, all of their paper was on the floor. It was a cruel practical joke to play on ones "friends." Fortunately, that never did happen around here.
These mechanical machines also had a bell inside which could be rung by the sending station to get the receiving stations attention. Perhaps it would come as no surprise that those folks with tape facilities did sometimes make a tape in a loop, which rang the bell on the receiving stations machine. A little of that went a long way and tended to not endear the sender to the receiving stations owner, his wife, his children, family pets or anyone or anything within earshot. That clever activity was usually only done once.
The characters sent on the earlier Teletype setups were made by sending each character in binary, i.e., with two tones. One tone was high and one was low and just like the binary ones and zeros of modern-day computer characters, each one or zero was represented by a tone, one shifted 850 cycles above the other. Teletype users later adapted a narrower shift scheme where the tones were shifted back and forth by only 170 cycles. To listen to a Teletype signal on the air you would be hearing the rapidly shifting tones, which were often called "diddles" since that word somewhat resembled the sound one heard.
Operation on RTTY on the low bands was lots of fun. Most of my operations were on 80 and 20 meters. The FCC rules required you to do this operation in the CW portions of the bands and the FCC had a requirement that any transmission on RTTY required that you had to identify your station both on RTTY and on CW. If a particular transmission lasted longer than 10 minutes (such as sending a picture or from a very slow typist) you must stop the TTY sending, identify the station on CW and Teletype, and then you could resume. It was not uncommon for people to send pictures, made from typing different typed characters, to others........ an early version of pictures that are now distributed over the Internet. The major difference was that these pictures were often complicated, had much poorer resolution, and if the signal faded or you received interference from a nearby station, the picture would be flawed, either with some missing data or some unwanted and scrambled printing. Only the strongest stations dared to send pictures on RTTY, particularly larger pictures which took a long time to send. Also, since the FCC required a CW ID every 10 minutes, you had to stop the picture sending, shift to a different tone which would not make the CW cause a flaw in the picture, ID your station, then return to normal and resume the sending. I remember one Sunday afternoon when a powerfully strong U.S. station was sending a taped picture that was well over 4 feet long when completed. It took well over an hour and there were multiple hesitations to IDentify the sending station. I remember the station was very organized and also very strong and I got a near perfect picture.
By the way, in order to get the shading just right on these pictures, the receiving machine had to be commanded to go over the same line several times printing different characters to get it just right. This meant that the machine on the receiving end could not be set up to automatically add a line feed <lf> when it received a carriage return <cr> command as was often the typical configuration. A picture might go over the same line multiple times to add different characters to provide just the right shading to the picture. Remember, also, that the only characters available to type were upper case letters, numbers, and several punctuation characters. Obviously, the person who created the original picture and tape to send it had a LOT of spare time on their hands and be very creative.
I gave up my TTY machines, because they took up so much space, were too noisy and smelly, and did not lend themselves to an environment for raising two boys. For many years after that, RTTY equipment changed, computers became available and software was written to allow technology to replace the old mechanical equipment. I don't know where all those old pieces ended up, perhaps in cellars and attics of some of the older hams. If they're in the attics, you'd better watch where you step or sit when you go visit your older ham friends. That heavy old WWII Teletype machine may be stored in the attic, right above where you might be standing or sitting. I've already admitted that my old tty equipment is gone so my hamshack is safe for you to visit.
The coming of sound cards for computers; first as a plug-in expansion card and later as a built-in function on the motherboard, has lead to some really nice and extremely versatile technology pieces with very useful software. Improvements keep advancing on both the hardware and the software. Teletype today is a far cry from that RTTY of yesteryear, and were probably all the better for that fact.
I decided, some time back, to rekindle my interest in RTTY and get involved in some of the digital modes now available to hams. It's uncommon, these days, to run across a home computer that does not have a sound card. The software offered to hams is feature-rich and much of it is free for the downloading. Many of my excuses dwindled when my logging program (Logger32 available at www.logger32.net) offered several sound card related programs as integrated pieces of the whole logging package which means, the decoder/encoder program was linked to the logging program and allowed a total, almost seamless, operation of these digital modes.
The two particularly popular digital programs are PSK31 and RTTY. I plan to spend some time in the near future trying out the PSK31 mode but I had a chance over a recent weekend to try the new RTTY (minus the noisy machines of the past). I had dabbled just a couple of times with the built-in features of my Elecraft K3 transceiver. The K3 has a built-in RTTY decoder, in addition to a decoder for PSK-31 and CW. The K3 is not the first piece of ham gear that decodes RTTY since the Icom IC-756PRO, PROII, and PROIII also have this feature. The K3 takes this several steps forward, however, by allowing the user to use the built-in CW keyer and transmit in CW (obviously), PSK-31, or RTTY. This means you can send in CW (at your choice of any speed) and it converts the characters input to PSK-31 or RTTY automagically. With the K3, you can operate RTTY (and PSK-31) on both RX and TX and not need a computer or sound card of any type.
Still, as complete as the K3's features are for these digital modes, I still wanted to use the integrated programs included with Logger32 (MMTTY and MMVARI) so I could have the automatic logging feature when I used these modes. Imagine being able to operate an RTTY contest and not touch the computer keyboard a single time, all activity being done at the click of a mouse.
To use the integrated programs, you do need an audio interface to tie your radio equipment to your computer. There are multiple circuits available on the Internet as well as in many of the books and magazines offered to hams. Enterprising hams can easily, and fairly inexpensively, build an interface for their station. There are also quite a few commercially built interface units if you don't choose to build your own. I went with the MFJ-1279 unit because it had the features I wanted, was in a cabinet smaller than I though I'd be able to build, and I was feeling somewhat lazy.
The helpfile for Logger32 provides much assistance for setting up these digital modes using the integrated programs. Typically the program MMTTY is used for RTTY and MMVARI is used for PSK-31 although MMVARI does have an RTTY component. By the way, these programs are available as stand-alone programs and are free and downloadable via the Internet. They really start to shine, however, when melded into the logging program to be "all things to all people" so to speak.
Theres a really neat video on YouTube that shows an old Model 15 as it printed out a message. Its at: http://www.youtube.com/watch?v=FWa6u5_Itvs and really brings back old memories. Typing at 60 words per minute, a modern-day computer user would marvel at the slowness of the old teletype printer over a current computer printer but it was what was available at little or no cost.
After seeing the video mentioned above, it reminded me that when I first got interested in computers, my old Teletype machine was my computer printer. I was using an MOS Technology KIM-1 computer, of which I sold many at my ham store. This would have been about 1976 and it preceeded the Apple, the TRS-80, and the Commodore PET. At that time, few printers were available and most hobbyists had to adapt an old IBM Selectric typewriter or a Teletype machine. I built an interface for my KIM-1 to my Model 19 machine and it was my computer printer for several years. I learned to program in BASIC on this system and that old Teletype machine printed out many program listings. Many are the times when I set that machine to printing and left for several hours to do something else while it completed the task.
I dare not continue as Im starting to get nostalgic and sad, thinking about "The Good Old Days." Truly, however, they really were good old days.
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Written September 27, 2010 - published TARC Newsletter October, 2011