 You are looking at a shelter mounted on a three-quarter-ton truck. Both are standard United States Army equipment. The shelter is small and compact, but big enough for its purpose. For it houses one of the smallest radio teletypewriter units available for tactical communications. Let's look inside. The combination of components you see mounted on the wall carries the nomenclature an slash g r c 46 The objective of this film is to acquaint you with its components and Provide you with an explanation of the electronic function of each component We'll also outline the capabilities of the a n g r c 46 and show it in operation First the components the ideal way to study the components of the a n g r c 46 Would be to assemble them one by one. So we'll do just that We'll mount the components on the rear wall of the shelter This balances the weight on the vehicle and maintains the desired compactness so that the controls of each unit will be accessible to the operator For sending and receiving teletypewriter messages will install a teletypewriter set The a n u g c 4 which is commonly called the page printer To increase the flexibility of teletypewriter communications. We will install a second teletypewriter This one the TT 76 is commonly called the reperforator transmitter It will enable the operator to record messages on tape and use the tapes for later transmission Next we will add radio equipment for transmitting and receiving the teletypewriter traffic The transmitter we will use is the T 195 The transmitter will also provide us with voice and continuous wave communication facilities Next to the transmitter. We will mount a receiver This is the r 392 it will receive voice Continuous wave and frequency shifted keyed signals The electronic signals provided by the teletypewriters are incompatible with the radio equipment Therefore, we will have to mount two additional components utilizing the space in the upper right The first of these is a radio transmitter modulator the md203 The modulator electronically converts the DC teletypewriter output impulses into frequency shift signals So that it can be transmitted by the T 195 transmitter The second required unit is this frequency shift converter the CV 278 The frequency shift converter converts teletypewriter traffic into DC impulses Electronically so that it can be fed into the teletypewriters We'll discuss the electronic functions of these units in more detail later in the film All the units we've installed thus far require electrical power for operation 28 and a half volts of direct current are required for the radio equipment The transmitter receiver modulator and converter The teletypewriters require 110 volts of 60 cycle alternating current The initial power source is of course the vehicle's battery The battery supplies the power to start the engine The engine drives an alternator The alternator provides approximately 28 volts of three phase alternating current The alternating current output of the alternator is fed into a rectifier and filter system Which converts it to approximately 30 volts of direct current After being fed through a voltage regulator The 30 volts of direct current is suitable for operating the radio components of the ANGRC-46 It also has two other purposes to serve First, it must be converted to the 110 volts of 60 cycle alternating current Required by the teletypewriters To accomplish this, we need one more piece of equipment This piece of equipment is a motor generator, commonly called a rotary converter And finally, after a voltage drop, it is fed back to the vehicle's battery for recharging We would like to point out here that another component is provided It is the interconnecting box J-1195 Used in online crypto operation, it is mounted on the shelf just above the floor Two converters are provided, one in use and one spare They are mounted on the floor We now have assembled the important functional components of the ANGRC-46 And provided some of the required power supplies for each unit Here are some of the accessories used most frequently This, the LEG-KEY-116U The loudspeaker, LS-166U And the microphone, M-29U Another device we will need is this interconnecting box J-668 It provides the receptacles, terminals and interconnectors Needed to electrically combine all the components of the ANGRC-46 The front panel of the interconnecting box includes power meters Various power off-on switches Fuses for the rotary converter and other circuits A function selector switch with controls And main power circuit breakers In addition to providing complete interconnecting facilities The J-668 also functions as a master power control for the ANGRC-46 This component must be readily accessible So we'll install it here, between the teletype writers in easy reach of the operator Another device we will need is this three position Send, mark hold, receive switch It controls the function of the teletype writers The send position connects the teletype writers for transmission The receive position connects the teletype writers for reception The mark hold position places both the page printer and the reperforator in a holding condition To the right is the tape distributor control switch for use when operating crypto equipment We can now complete the installation by making all the necessary cable connections This ANGRC-46 is ready to begin operation We've seen and installed each component of the ANGRC-46 We will now examine the electronic function of the transmitter, receiver and teletype writers And see how the modulator and frequency shift converter make them compatible This explanation will be simplified, but it will be fundamentally accurate The transmitter generates what is called an RF signal, which we will represent with this wavy line If we were to examine a portion of this RF signal, we would find that it has two characteristics It has frequency, represented by the distance between these two points And it has amplitude, represented by the distance between these two points Since it is this RF signal, which is eventually sent out over the airwaves We must add to it any information which we wish transmitted One method of doing this is by shifting the frequency Notice that these distances are now changed A second method is by varying the amplitude, the distance from top to bottom Notice that now the distances between the top and bottom peaks which represent amplitude are varied This signal now has varying amplitude Now let's examine the signal provided by the teletype writer We'll let this line represent the output of the teletype writer When the teletype writer keys are operated or a tape message is fed into the reperforator Direct current impulses are created These impulses represent current flow But in reality, they will not be as orderly as this For the various letters and symbols of the teletype writer machines create various combinations Like this for letter t Or like this for letter r Or like this for letter b So we have an output signal containing various combinations of dc impulses A signal that accurately represents the message typed on the teletype writer The teletype writer output signal of dc impulses must shift the rf carrier frequency of the transmitter The modulator performs this function Both the rf signal from the transmitter and the dc current impulses from the teletype writer are applied to the modulator The modulator produces a shift of the rf frequency for each current pulse applied This is the result, an rf frequency shifted signal Every time a key is pressed on the teletype writer dc impulses are created in the teletype writer's output In the modulator these same impulses cause the rf carrier frequency of the transmitter to shift in frequency This signal has been keyed by shifting its frequency. Thus the process is called frequency shift keying In the transmitter the signal is amplified and transmitted When receiving teletype writer traffic the process is reversed An rf signal containing the teletype writer information in the form of frequency shift keying Is picked up by the antenna and fed into the receiver From the receiver it goes to the frequency shift converter The converter reverses the actions of the modulator It utilizes the frequency shifts in the rf signal to create dc impulses Which are fed into the teletype writer. The dc impulses operate the receiving teletype writer Which then duplicates the teletype writer traffic transmitted by the distance station We use this radio frequency carrier signal to send voice and teletype writer messages at the same time Since teletype writer communications varies only the frequency of the rf signal We can utilize varying amplitude to carry voice communications Both variations can be carried at the same time This allows the angrc-46 to offer the feature of simultaneous voice and teletype writer operations Now that we understand the electronic functions of the equipment Let's examine the capabilities of the angrc-46 The frequency range of the t195 transmitter is from 1.5 to 20 megacycles in 10 bands The transmitter has an automatic tuning feature which allows up to eight channels to be pre-tuned This allows fast efficient tuning of the transmitter The frequency range of the r392 receiver is broader than that of the transmitter It operates from 0.5 to 32 megacycles in 32 bands Unlike the transmitter, it has no automatic tuning feature and must be tuned manually Three types of service are provided by the angrc-46 Continuous wave operation using the hand key Voice operation using the microphone Logistical support requests this command Delta alpha two one one slash three six Teletype writer operation utilizing the page printer Or the reperforator And as we learned earlier simultaneous voice and teletype writer operation Simultaneous cw and teletype writer operation cannot be obtained The tactical range of the angrc-46 is measured in terms of the ground wave The ground wave follows the curvature of the earth and provides a reliable range of approximately 80 kilometers with the angrc-46 This distance is given in approximate terms because it will vary according to terrain and atmospheric conditions In addition to the ground wave, there is a sky wave component The signal radiated by the antenna being reflected by the ionosphere over long distances The sky wave range is subject to many variations Depending upon the conditions of the ionosphere the terrain the operating frequency and the type of antenna system Average sky wave distance is over 1600 kilometers, but it is not generally used for tactical purposes Some of the capabilities of the angrc-46 are determined by the antenna system The antenna provided is a five section 15 foot whip It is mounted high on the outside front panel of the shelter Inside it is connected directly to the transmitter When only one antenna is used there is an additional interconnection between the transmitter and receiver This jumper allows the antenna to be switched from the transmitter to the receiver and vice versa Thus the one antenna serves in both transmit and receive What we see here is called half-duplex operation Traffic can be transmitted Or received, but not simultaneously For duplex operation a second antenna is required and it must be located at least 15 meters from the first antenna Additionally the transmitter and receiver must be tuned at least one megacycle apart For duplex operation cabling changes which require higher echelon personnel are necessary Due to antenna requirement duplex operation while mobile is not possible Other capabilities of the angrc-46 can be seen by watching it in operation We'll assume the operator has a high priority message for an air ground liaison team First he checks the frequency call signs and authentication Then he checks the channel band frequency chart This tells him which channel has been pre-tuned to the frequency he wants In this case it is channel six He turns the preset channel selector switch to channel six and the transmitter is automatically tuned to the desired frequency Since this is to be a voice call the service selector switch must be set to the voice fsk position This position is for radio telephone and or radio teletype writer transmission The other positions are stand by used to conserve power when not actually transmitting Cw used for continuous wave transmissions Calibrate to provide a means of tuning the receiver to the transmitter and vice versa The remote position is used to provide remote operation of the radio facilities He then turns the test key to the on position and holds it there until the tuning indicator light comes on When it does the antenna is loaded The receiver is then manually tuned to the same frequency He is now ready to make a preliminary call alpha eight. This is alpha bravo three over Alpha bravo three This is alpha alpha eight over Alpha alpha eight. This is alpha bravo three I have a radio teletype message for you over This is alpha alpha eight Send your message over The operator inserts a pre-cut tape into the transmitter distributor He then places the send mark hold receive switch in the send position He makes the necessary switching arrangements on his page printer And sends the teletype writer message The angrc 46 should serve to handle almost any teletype writer traffic problem Thanks to the flexibility provided by the two teletype writers for in addition to the page printer's ability to transmit and receive There is the reperforator's ability to record incoming traffic on tape Messages typed on the reperforator are also recorded on tape. The taped messages can be transmitted immediately They can also be stored for later transmission This ability to record a message on tape is advantageous in situations where a message must be repeated to several addresses The operator of the angrc 46 has other responsibilities in addition to the actual operation of the equipment Operator maintenance of the wire mesh filter in the t195 transmitter must be accomplished daily After removing the cover the filter is removed by unfolding the wire handles and pulling straight out The transmitter should never be operated without the filter three of which are provided one in use and two spares Instructions for cleaning and lubricating are printed on the side of the filter and should be rigidly adhered to He must protect himself by always seeing that this protective rubber cover Is securely mounted over the antenna binding post Contact with the antenna circuit can result in severe rf burns The functional components you see here are used in several different models of radio teletype writer sets The angrc 46 Utilizes this s 89c shelter made of steel and weighing 1,400 pounds The angrc 46a Utilizes this lightweight shelter Made of aluminum and weighing 1175 pounds The angrc 46b utilizes this s 144 shelter made of aluminum and weighing 1110 pounds This b model is particularly designed for use with online cryptographic equipment In the angrc 46b are the usual racks to accommodate the equipment on the far wall And these additional racks on the left wall which accommodate a security device And security files When mounted in an armored personnel carrier, the equipment is called the angrc 29 This is the radio transmitter t 195 grc 19 It is here because we have an important point to make Let's remove the case from this t 195 and look inside For angrc 19 operation one cable goes to the exciter sub chassis The other connects to the rear of the front panel Modifying the transmitter of a grc 19 for operation as the transmitter of an angrc 46 Is accomplished by reversing the connections of these two cables It can be performed in a matter of minutes by maintenance personnel This film has offered orientation in the components capabilities and operation of the radio teletype writer set angrc 46 more detailed information concerning the correct tuning procedures And proper maintenance of this equipment can be obtained from the various manuals provided for the unit and its components The angrc 46 can transmit and receive traffic by continuous wave Voice teletype writer over a reliable distance range of 80 kilometers It can provide simultaneous voice and teletype writer operations And it can offer these facilities in a mobile package For it is one of the smallest radio teletype writer units available for tactical communications It is a valuable piece of equipment one with which you should be thoroughly familiar One which deserves careful attention to operation and maintenance procedure