ELECTRONIC WARFARE NOSTALGIA
Pre-"AN" Navy Systems ( Nostalgia )
In the very early fifties, life as a sailor was relatively simple, as were the electronic equipment designations. In those days ( from my limited viewpoint as a destroyer escort (DE) sailor ), every self-respecting radarman wore a collection of different-colored grease pencils in their dungaree shirt pocket. Radarmen had been taught to write backwards and upside down, so that we could position ourselves behind Plexiglas displays and print target information to be read by the evaluator, in front of the board. We also stood on one side of horizontal plots and wrote upside down for the benefit of those standing on the other side. Great innovations, from our point of view, were such labor-saving features as the PPI range bug, and the parallax plotting head. Those were the days of bed-spring antennas, when the 6SN7 vacuum tube triode was king, and pipology was employed to locate weak targets in the grass and analyze target pips. On the SU surface search radar, for example, we determined the bearing and range to a target by actually stopping the antenna, scanning the target manually for maximum return ( the maximum pip size on the A-scope ) and turning another crank to run the step out to the leading edge of the pip and reading the range in yards from a mechanical odometer-type counter. We had to do the same thing with the air search radar, the SA. The side lobes on that radar resulted in targets having bearing widths of more than 90 degrees! Around 1952, I remember, we received a couple of field changes to the SU, which permitted us to determine ranges "on the fly", by cranking out a bug superimposed on the radar sweep and bisecting the blip on the PPI scope. It was less accurate, but saved wear and tear on the antenna servo systems. Back then, radiomen were expected to maintain and repair their own equipment, but I guess radarmen were considered to be of lower intelligence, because we were limited to preventive maintenance ( how I hated it when someone referred to it as "preventative maintenance"). In retrospect, the frequent opening of the equipment for dusting and debris removal probably caused more equipment failures than if we had left them be. There was always the danger of pinching wires and breaking wires and electrical contacts by the frequent opening and closing of equipment drawers, getting screwdrivers wrenched from our hands by magnetrons, and discharging capacitors with the home-made safety tool called the shorting probe. With no air conditioning, we sometimes had to try to cool the equipment by setting the battle short and opening drawers, removing panels, and sometimes directing fans at the tubes. Yep, those were the days. Below is a list of some of the equipment which I recall operating and encountering in the repair shop ( errors, if any, are due to the dimness of memory -- help by way of corrections and additions is always appreciated )...
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RADARS, RADAR REPEATERS, ECM EQUIPMENT, and RADIOS
SA - Air search radar with A-scope, manual antenna controls, and PPI scope which the operator had to straddle to get close enough to reach the console controls. The antenna was a small bed-spring array, which we could control by a large crank on the console.
SC - Air search radar with A-scope and large bed-spring array (these were installed on the larger ships)
SG - Surface search radar with a clam-shell antenna, which allowed a quick zenith search to determine the altitude of aircraft directly overhead.
SK - Air search radar, similar to the SC, I believe. I recall that the antenna was quite large, and could be carried only by larger ships.
SP - A height-finding parabolic antenna with a neutating dipole, similar to that of fire control radars. Altitude was a function of the vertical angle of the antenna.
SU - Surface search radar with A-scope and PPI scope. This had a covered parabolic antenna controlled by small crank on the console.
SX - Air search and height finder radar generally installed on larger ships. It had two orthogonal "banana-peel" antennas.
RADAR REPEATERS (all of these were PPI scopes)
VD - A weather-proof PPI scope placed on the bridge of a ship. It had one large dial to turn a mechanical cursor to estimate bearings, and had a set of range rings with which to estimate range. Later versions were equipped with parallax plotting heads. Unkind words would be shouted down the voice tube in Combat Information Center (CIC) from the Bridge if the Officer of the Deck (OOD) spotted an unreported blip in his VD repeater!
VF - A radarman's radar navigation dream, but a technician's mechanical monster. This repeater had a small PPI scope and an equally-small B-scope, which magnified a small sector defined by two bearings and two ranges. This provided more accuracy and target definition. We used the VF for radar navigation by maintaining the target blip for a known object, such as a fixed tower in the water, on the B-scope, and plotting its range and the reciprocal (e.g., adding 180 degrees) of its bearing on the applicable navigation chart.
VG - A horizontal semi-opaque frosted glass plotting board (about 36 inches in diameter) upon which a PPI display was projected from underneath, allowing the operator to mark the targets with a grease pencil. As I recall, the projector seldom worked, but the VG made a great general plotting board and table for holding tactical publications
VJ - A PPI scope with range bug and mechanical cursor. Some versions had a pedal-actuated electronic cursor which generated a cursor on the phosphor. The radar sweep disappeared during the time the electronic cursor was activated, so you had to get that cursor positioned while the target pip was still persistent.
VK - Considered a modern marvel by its operators, the VK had an two extra pairs of servo dials that allowed the operator to offset the origin of the sweep to any position on ( or off ) the face of the scope, and to likewise offset and manipulate an electronic cursor independent from the sweep. It was ideal for use by air intercept controllers for controlling CAP aircraft. For example, the operator could put the origin of the cursor on the blip representing the CAP, and position it to intersect a blip representing an enemy aircraft, and then advise the CAP pilot of the bearing and range of the enemy aircraft from the CAP.
DBM - Direction finder. Displayed a lobe of the detected signal.
RDJ - ECM pulse analyzer. This was used in conjunction with the RDO below.
RDO - Intercept receiver. A manually-tuned receiver. There were various tuners associated with this equipment. To change bands, you physically removed one tuner and replaced it with another that covered the desired band.
TDY - A jammer. We never used ours during the two and a half years I was aboard the ship.
- There were many types of radios, but those listed below seem unforgettable, somehow.
MBF - HF radio transceiver characterized by two features: (1) it had a positive ground on an isolated chassis, as I recall; and (2) It looked like and was used in the same manner as a squawk-box (push the lever and talk into the speaker).
TBS - THE tactical HF radio. The letters stand for "Talk Between Ships", but I'm sure that all of our tactical signals were heard 'round the world.
TDZ - Used heavily by air controllers, this had the "Collins Autotune System" - a mechanical marvel if it worked. It was always entertaining to watch, when the radio operator changed VHF channels - a dozen or so dials all automatically rotating back and forth to arrive, hopefully, at the correct frequency.
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A-scope - An oscilloscope display in which targets appear as pips on a horizontal line representing a time base. Target range is analogous to the horizontal position of the deflection from one end of the time base (at which the transmitter pulse may appear as a large pip. The amplitude of the vertical deflection is a function of the signal strength.
Air intercept controller - A radar operator who is controlling CAP aircraft by observing its position on a display and direction the aircraft's movements for a specified mission, such as intercept of enemy aircraft.
B-scope - A high-persistent cathode ray tube (CRT) display in which the target appears as a blip in a sector bounded by two bearings and two ranges, with bearing indicated by the horizontal coordinate and range by the vertical coordinate. Intuitively, the B display is a "chunk" of the PPI display in which the target of interest appears.
Battle short - A switch that bypassed all interlocks on a piece of equipment. So named because it eliminated interlock failure during battle conditions, when vibrations during battle might cause the equipment to shut off inadvertently.
Bed-spring antenna - A rectangular antenna having a wire grid reflection configuration on which a number of dipoles are mounted. So called because it resembled an old-fashioned bed spring.
Blip - A stationary spot of contrasting luminescence on a PPI display, indicating the presence of a target. The blip is formed at a distance from the origin of the PPI sweep analogous to the target's distance from the radar as the PPI sweep passes the direction of the target. A PPI blip had persistence, that is, it usually remained visible until the radar antenna again pointed to the target, thus refreshing the blip ( in a slightly different position, depending on the relative distance and speed between the radar platform and the target ).
Bogey - Code word for "unidentified aircraft".
CAP - Combat Air Patrol. Aircraft whose mission usually is to intercept adversary aircraft.
Clam-shell antenna - A radar antenna resembling an open clam shell. The vertical portion is used to focus the radar beam for a standard surface search. The radar energy is transferred to the bottom part of the antenna in order to perform a zenith radar search, such as to determine the altitude of an aircraft passing overhead.
Electronic cursor - An operator-controlled sweep on a PPI which in independent of the radar sweep, allowing the operator to determine the bearing and range to a target without the need to stop the antenna. There are usually two hand cranks associated with an electronic cursor, one to rotate it in azimuth to determine the bearing of a target, the other to move a range bug on the sweep to measure target distance. On some radar repeaters, there is an additional pair of hand cranks to move the origin of the sweep in order to measure range and bearing from one part of the PPI scope to another (such as between a target representing a CAP and another target representing a bogey ).
Field change - An improvement to a piece of electronic equipment which can usually be performed by field personnel. The field change contains all needed parts and instructions for installation and operation.
Grass - Random vertical deflections on an A-scope caused by noise and interference and possibly jamming. So called because it resembles a line of grass on the display.
Grease pencil - A colored crayon with which to mark Plexiglas plotting boards, display boards, and Plexiglas PPI scope covers for tracking targets and jotting information.
Interlock - An automatic switch designed to turn off a piece of equipment if a panel was removed, or a drawer opened, etc.. This was a safety feature to prevent inadvertent electrical shock from live circuits to persons reaching into the equipment, etc.
Leading edge of the pip - That portion of a pip that is nearest to the origin of the A-scope display.
Mechanical cursor - Generally a bearing line on a PPI display cover that can be rotated to bisect a target, thus giving indication of target bearing.
On the fly - Measuring target data without stopping the radar antenna. For example, positioning the range bug of a PPI at the estimated range of a target, then observing any distance between the range bug and the target blip on one sweep, and correcting the range bug position to reduce the error on the next sweep. When the range bug bisects the blip, then the range is read from the range counter.
Parallax plotting head - Actually a series of two or more parallel Plexiglas covers, at least one of which is edge-lighted so that the etched cursor is actually projected on the PPI, resulting in a more accurate indication of bearing.
Persistency - A property of the PPI scope that resulted in a blip remaining visible (but fading) after the sweep passed over it. Each time the sweep passed over the target, the blip would be refreshed to its original brightness.
Pip - A vertical (usually) deflection of an oscilloscope sweep due to presence of a target.
Pipology - The analysis of pips to determine target characteristics, largely an art pursued by experienced operators.
PPI scope - Plan Position Indicator. A high-persistence cathode ray tube (CRT) on which the radar azimuth is represented by a bright line, or sweep, and targets represented by brightening of the sweep at the range of the target. The distance from the sweep origin to the edge of the CRT represents the maximum range observable with that particular sweep.
Preventive maintenance - Routine maintenance, performed usually by operators, on operable equipment in order to keep the equipment in peak functioning order.
Radar sweep - A bright line on the PPI scope which represents the position of the radar antenna. The sweep rotates with the antenna, and provides indications of received target signals. With a gyroscope signal input, true North was at the top of the display, and the bearings to targets were "true bearings"; otherwise, the top of the display represented the direction directly ahead of the ship, and bearings were "relative bearings" (i.e., relative to the ship's heading).
Range bug - A spot on the radar sweep or electronic cursor, brighter than the sweep or cursor itself, which can be moved along the sweep to indicate range from the radar location.
Range - Distance from the radar origin to a target.
Range counter - An odometer-like display that is usually controlled by the range crank to indicate target range.
Range rings - A series of equally-spaced bright spots on a radar sweep, which forms concentric circles as the sweep rotates. The concentric circles are at fixed ranges (e.g., 10 nautical miles), allowing the operator to estimate a target range by interpolating the target blip's position relative to the nearest range ring.
Shorting probe - A home-made device usually consisting of a wooden handle about 8 inches long in which was inserted a 12-18 inch copper rod, bent into a "U" at the end so that the whole thing resembled a copper cane stuck into a piece of wood. A long braided copper strap, about 24 inches long, was braised to the rod near the wood handle, and a large alligator clip soldered to the other end. When a piece of electronic equipment was opened (hopefully with the power off), we were supposed to clip the braid to an unpainted part of the chassis, and gently touch the rod to various bare wires and terminals in order to discharge any capacitors before going in to work on the equipment. We frequently observed displays of sparks, and occasionally formed melted pits on the rod - a true "hammer and tongs" approach to safety.
Squawk-box - Intercom (IC) unit. Select one or more stations to address, then press the "Talk" button and speak into the speaker. Releasing the "Talk" button allowed the operator to await messages from other stations.
Step - A break, or discontinuity, in an A-scope sweep that can be moved by positioning a range crank to allow the measuring of target distance ( the step was usually aligned with the leading edge of the pip, and the corresponding range read on the range counter.
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August 13, 2004 03:34 PM -0400