Western Historic

 RADIO MUSEUM

Radio Teletype - RTTY - with Real Machines

Teletype Corporation Machines

RTTY Terminal Units

W7HTR - Real Machine RTTY Amateur Radio Station

photo:  JA1DI - Isao Yamaguchi, Tokyo, Japan - from RTTY QSL - 1 MAR,1975

Teletype Corporation

Model 19 - Military A/N TT-7/FG

 I have owned this particular Model 19 since 1975. I purchased it from a long defunct company called RTTY Electronics in the California SF Bay Area. The sole employee of the company rebuilt teletypes in the basement of his house. What a basement,... full of different kinds of teletype machines and parts. He had a washing system that used solvent (kerosine) to degrease the printers and a metal wash tub basin to capture the run-off. It was an experience just to go there and see all of the machines in various states of assembly and disassembly. Needless to say, this Model 19 has always been in great condition - almost like new inside, probably because thirty-some-odd years ago, new parts were still easily available. I paid $125 for it and hauled it back up to Nevada in the bed of a 1969 Datsun pick-up (pulling Luther Summit was quite a load for the little 1200cc engine.) I used the machine actively on 20 meters from 1975 up to about 1980, working several DX RTTYers like DU1POL, Paul Lacap, who was the chief of police in Quezon City in the Phillipines, or JA1DI, Isao Yamaguchi in Tokyo, Japan (see header photo.) Many stateside RTTYers were also worked with this old Model 19. In 1980, I moved from Gardnerville, Nevada to Minden, Nevada and had no room for the RTTY station at the new QTH, so I stored the TTY from 1980 until 1993, when we moved to Virginia City, Nevada. In 1995, I went through the machine, lubing and adjusting, in order to have it as a working exhibit in our radio museum. The only problem was I couldn't find any RTTY signals on 20 meters at that time,....at least 45 baud Baudot signals (except for one lone XE1 station that was copied.) I assumed that real machine RTTY was dead. In 2007, I again resurrected this Model 19. I had to replace the 323B grid-controlled thyratrons in the REC-30 loop supply in order to get the tape perforator working but otherwise the machine was still in fine operational condition. This time many 45 baud Baudot signals were copied especially during contests. It was great to again find that the Model 19 along with an old HAL ST-6 would print out solid copy with that fabulous electro-mechanical cacophony that is real machine RTTY. This Model 19 is the later version with the tape perforator counter mounted to the left of the keyboard inside the perforator housing. This mounting made the mechanism less likely to sustain damage compared to the earlier right side mount. The machine is military in origin and has holding magnets in the printer (connected in parallel for 60ma operation.) Military designation was TT-7/FG. The gray color was probably a later addition courtesy of RTTY Electronics. This machine is still active - see our RTTY station below.

Teletype Corporation

Model 19 - Bell System

This is an earlier version of the Model 19. It is the configuration that was mostly used by the Bell System and other non-military users (like Western Union) for various functions like TELEX or WU communications. The obvious difference is the mounting of the tape perforator counter on the right side of the keyboard. Other indicators that this is an early example of the Model 19 are the wooden rollers in the platen assembly and in-table shock mounts for the base. These shock mounts are very effective at quieting the machine operation. This Model 19's printer uses the standard pulling magnets that are connected in series for 60ma operation. The loop supply is the REC-6 utilizing a large copper-oxide rectifier. The REC-6 loop supplies were usually not used by the military. The keyboard of this machine has a "Bell Systems" tag mounted on it. I obtained this machine in October 2007 and, though it was in fairly good operating condition, it was missing some parts and had been somewhat neglected as far as lubrication and adjustment. A thorough disassembly and cleaning of the printer, keyboard, TD and tape perforator, replacing the missing parts and correcting several wiring anomalies in the table and base, got this Model 19 operating smoothly and accurately. This Model 19 is set up as a "working display" in the museum. It can run on local loop for casual demonstrations for museum visitors or it can also operate using vintage RTTY gear - if there are any RTTY signals on the bands, that is.

Hoffman Laboratories Inc.

U.S. Army Signal Corps  -  CV-116/URR

The CV-116 is a diversity RTTY FSK TU that was designed for the Signal Corps to be used with two R-390 receivers for space or frequency diversity RTTY. Using 45 tubes and weighing in at nearly 70 lbs., the CV-116 uses the 455kc IF output from one or two receivers for its signal input to each channel. The input stages are similar to a receiver's input in that an RF amplifier, oscillator and mixer are used in each channel. Channel A operates at 50kc and Channel B operates at 29.3kc into their respective discriminators. Although crystal control can be used, AFC is also available to compensate for receiver (or signal) drifting. There are two, motor driven AFC controls that use amplifier circuits in feedback loops to drive motors that gear drive a tuning condenser that keeps the oscillator tuned for each channel. The red lamp is an addition that provides a visual alarm indication that the driven AFC condensers are near the end of travel. Normally, the internal bell gave a warning alarm but if several CV-116s were in use with several TTY machines, it would have been difficult to find which CV-116 was giving the bell alarm, thus this addition which provides both alarms. The second from the left meter (M4) can be switched to monitor several areas of the circuit including the built-in, adjustable loop supply. The CV-116 is designed to drive the TTY printer magnets directly (cable interface required) and will drive resistive loads from 125 to 500 ohms. This Cadillac of military TUs was built in 1953. It is fully functional and in use with a R-390A receiver to copy RTTY on the Model 19 TTY.

Hoffman Radio Co.

U.S. Navy  -   CV-89A

 The CV-89A was part of the URA-8 diversity RTTY system that was built for the Navy by Hoffman Radio Company. Two CV-89A units were used with a combiner unit to achieve space diversity and reduce fading signals to improve RTTY copy accuracy. Using 15 tubes, the CV-89A is modular in construction. Five modules make up the unit - four are mounted in the chassis and one is mounted in the back of the case. Being an audio discriminator device, the operator has to tune the RTTY signal so the mark and space frequencies straddle the center frequency of the filter selected. Narrow shift center frequency is 1000hz and wide shift is 2000hz. The CV-89A features a built-in oscilloscope display to aid in tuning and determining FSK shift. The oscilloscope display will shift vertical positions with mark and space frequencies and by adjusting the shift knob so the display spreads between the three graduations on the display scale, frequency shift can be measured. The CV-89A requires a separate loop supply in series with the printer magnets. The magnets and loop supply can be connected to the rear A/N MIL connector (14S-9P) or if the TTY/loop is set-up with a single .25" phone plug, it can be inserted into the jack on the front panel behind the small door in the lower right panel. An excellent, easy to use military TU. Built in 1953, this CV-89A is fully functional and provides great copy with any receiver that has a 600 audio line out.

Northern Radio Company

Type 153 Model 2

This is a Tone Frequency Shift Keyer built by Northern Radio Company. It is a dual channel unit and both units are completely independent of each other. Fixed tuned filters are used and are set for 85 Hz shift. The tones also use a Mark frequency that is higher than the space frequency. This suggests that this TU may have been used in the VLF wavelengths. It has also been reported that the government state department used the 153 in their RTTY feeds to the VOA stations.12 tubes total are used, six in each unit. I have never used this TU since it is such an odd, apparently special function unit. Mid-fifties vintage.   

Dovetron

 MPC-1000RC - Multipath Diversity RTTY TU

Possibly the most electronically elaborate RTTY TU ever built for use with real machines. The MPC-1000RC can do speed conversion, multipath correction, auto-start, AFSK and has a multitude of other abilities depending on the users requirements and the TU's options. The MPC-1000RC features front panel tunable filters for Mark and Space from which shift can be determined. Originally, the Dovetrons used a CRT display but later a SSD "Cross-fire" LED display could be installed to replace the CRT. The Dovetron shown has the LED display option installed. Mostly op-amp technology but a considerable amount of digital CMOS in the UART board which does the speed conversions. The MPC-1000RC provides an adjustable built-in loop supply to directly drive the printer magnets. A fantastic TU that really has the great performance to go along with its great looks. Built in 1976.

Dovetron

MPC-1000CR/T  "Tempest"  RTTY TU

Though the Dovetron Tempest looks very similar to the civilian MSR-1000RC, it is the military/government version of the TU and MIL-SPEC is used throughout the unit. The Tempest units will have BNC connectors for inputs and outputs on the rear and a 14S-7P power input connector. Speed conversion, diversity capability, duplex afsk and tunable mark and space filters are the standard features but the Tempest versions do not have the auto-start feature or the keyed TTY loop supply. FSK polar outputs are provided to drive a loop keyer for machine RTTY or whatever else you might want to use. Both +/-6vdc and +/-12vdc FSK polar outputs are provided. The MPC-1000CR/T shown is in the "self-test" mode to show the SSD "Cross-fire" LED display operating. The horizontal line indicates mark and the vertical line indicates space. A fabulous TU for RTTY built in the early 1980s.  

HAL Communications Co.

ST-5

The ST-5 was one of the first TU's to use op-amp technology utilizing the 709C op amp. It came out in 1970 and was available as a kit. Build quality varies considerably. The circuit uses toroid based filters and features a built-in loop supply that is keyed for direct connection to the printer magnets. Later models featured auto-start.

HAL Communications Co.

 ST-6

The old stand-by,...the reliable ST-6 was (and is) the work horse for real machine RTTY. Using toroid based filters and op-amp technology, the HAL ST-6 is easy to operate and it is easy to tune in stations. The ST-6 is built on eight circuit boards which plug into sockets that are mounted vertically. The meter is cheap and rarely accurate. Some meters are illuminated but most aren't. Early versions of the ST-6 use .25" phone jacks for TTY outputs and RCA phono jacks for inputs. The later versions will have Molex connectors for the TTY outputs. Many ST-6s were sold as kits and therefore the build quality can vary dramatically. When well built, the ST-6 is indestructible and always reliable. Even if you do have to work on the ST-6, it is well laid out and easy to troubleshoot and repair. Too bad it doesn't have the Dovetron looks. Built in the mid-1970s.

Flesher Corp.

Model TU-170

This small TU is mostly op-amp technology and uses active filters for mark and space tuned circuits. It has a built-in loop supply and also has auto-start capabilities. The plastic and metal case is small for the amount of circuitry inside. Dates from the mid-1970s.

Electronics International Service Corp. (EISC)

Model TV1-C  "TELE TERMINAL"

This TU is a basic unit that provides only TTY decoding with a built-in loop supply. Discrete transistor technology and toroid based filters make this a very simple unit to work on. Normally the AFSK oscillator output would be connected to the microphone input of a SSB transmitter which resulted in FSK signals - at least that was how it was done in the seventies. This TU provided a mic input on the back and then the operator could select RTTY or Voice from the switch and not have to disconnect cables. The TU itself does not have AFSK capabilites. The meter is dated February 1971. 

W7HTR Homebrew TU

I designed and built this op-amp based TU in 1975. I decided to use active filters as they were the current "buzz word" at the time. Unfortunately, active filters require a sine wave input and the square wave output of a standard RTTY TU limiter wouldn't work correctly. I used an op-amp based AGC IC (LM-380) for the input so the filters would always "see" a sine wave regardless of the input signal level. At first I had the Q so high on the filters tuning in a signal was next to impossible. The filters have to overlap somewhat for ease of tuning and good copy and this was accomplished with a lower Q in the filters (RC component change.) My AFSK circuit used an Intel "Function Generator on a Chip" (you used to be able to get them from PolyPacks - remember them?) I switched between two fixed 1% MF resistors using a DG-200 micro relay and the system worked quite well. For local copy, I split the output of the AFSK buffer to also drive the input of the TU during transmit. This resulted in an actual received copy on the printer and not the local copy that results from breaking the local loop. I all worked pretty good and I used this TU from 1976 until 1980. Ugly, isn't it?

NOTE: I also built one of the W2PAT tube-type TUs in 1975. It used neon lamps indicators and had TV-type adjustable coils in the filters. I later changed the filters to toroid based and the whole thing worked much better. I wish I still had it but I torn it up years ago for parts for some other project.

W7HTR RTTY Station

RTTY Rack...This rack contains all of the gear that we can use for real machine RTTY. Upper-most is the Navy CV-89. Next is the Dovetron Tempest, then the CV-116, which is connected to the IF output of the 1955 Collins R-390A, followed by the civilian Dovetron TU. Below that are the patch bays which takes the place of a multitude of switches and provides 96 inputs or output to the various pieces of equipment. Between the patch bays is the remote keyed loop supply - necessary for the Dovetron Tempest and the CV-89 TUs. At the bottom is a rack mount 600 ohm speaker connected to the local audio from the R-390A. The receiver's 600 ohm Line Audio can be routed to any of the TUs via the patch bay.

On the shelf...The HAL ST-6 workhorse TU which is normally connected to the 75A-4 receiver. A dual speaker assembly is on top of the ST-6 and it connects to the 4 ohm local audio outputs from the Collins 51J-2 and the Collins 75A-4 receivers.

TTY...Military Model 19, TT-7/FG

Transmitter: Collins KWS-1  SN 616  ... I've owned this KWS-1 since 1970. I bought it from the original owner then for $600. At the time, the KWS-1 was still a fairly new transmitter (only 14 years old) and they were only just beginning to come down in price from the original $2000+ price tag. The KWS-1 will run 1KW PEP on SSB and 1KW on CW. This is input power with 2KV on the plates of the 4CX250Bs with 500mA of plate current. When operating AM or RTTY, power has to be reduced since these are 100% duty cycle modes. I usually run 400W input power in RTTY by controlling the audio level of the AFSK oscillator input using the audio gain control on the KWS-1. This KWS-1 is mostly original. The 4CX250B tubes are later types than the original 4X150s and the 866 MV rectifiers have been replaced with 3B28s. In 1991, I did a thorough check-over, an alignment and found the transmitter to be in good shape. In 2006, I was having problems with remote PTT and with loading stability. I discovered that the flex cable connection on one of the roller inductors had broken loose was causing the stability problem. The PTT problem was also a broken wire in the microphone input connector. The KWS-1 is a great transmitter - versatile, high power, great audio - and this is from someone who has owned their's for 35+ years.

Receiver: Collins 75A-4  SN 875 ... I've also owned this 75A-4 since 1970. I bought it from Ham Radio Outlet in Burlingame, California. It was my first really good amateur receiver. It had all of the Collins' upgrades installed when I bought it, so all I've done over the years is replace the "Black Beauty" caps, replace the filter caps and normal routine maintenance. The receiver has a 800hz filter, a 3.1kc filter and a 6.0kc filter installed. It has always been a great receiver for RTTY (and CW and SSB, too.)

Receiver: Collins 51J-2 ...This receiver is actually the end result of a total rebuild using two "not-so-good" 51J-2 receivers to make one good receiver. One had a trashed gearbox and the other one had been "hamstered" with lots of unnecessary modifications that were all poorly installed. The receiver barely functioned and then only intermittently. The "rebuilt to original" 51J-2 is very sensitive and, of course, Collins accurate. It's a great general coverage receiver and was one of the favored receivers of the Signal Corps for RTTY - until the R-388 came out.

Receiver: Collins R-390A ... I got this receiver as payment for repairing and aligning a fellow ham's R-390 receiver. This is a 1955 contract built by Collins and I completely went through the receiver to assure that its performance was up to its design capabilities. Simply a great receiver.