Old - Ricks Career With ATC

Rick's Career
With Air Traffic Control
Rick's Career With ATC
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Broadband - Two Generations of Displays

   Radar Bright Display Equipment (RBDE)
   Plan View Display (PVD)  

Plan Position Indicator (PPI) Display

This is a  generic display of a PPI scope. It is typically what most people think  of as a radar display, and was widely used in air traffic control until  the introduction of raster displays like the RBDE and PVD scopes.

Historically the controller's PPI display would update in synchronism  with the radar in real time. The image was not stored in a computer only  displayed on the screen. The PPI cathode ray tube had a very long  "persistence," meaning the image would fade away very slowly, allowing  the controller to view it for a few seconds. Before the image faded completely, the radar would make another sweep and refresh the image. Because the image grew dim as it faded, it was necessary to make the  radar room dark.

State of the Art PPI Display

This is the state of the art in Cathode Ray Tube radar technology iin 1948. This was probably the largest glass tube available and the threat of an implosion was very real. Hence, the air gap and double glass on this particular console.

Various phosphors were available depending upon the needs of the measurement or display application. The persistence of the illumination depends upon the type of phosphor used on the CRT screen. Phosphors were available with persistence's ranging from less than one microsecond to several seconds. For visual observation of brief transient events, a long persistence phosphor was desirable.

Position Controls

        ZLC c1974

The PVDs are flat emulating a raster scan RBDE scope. The display mode (analog/digital) of the PVD was selectable from a single push button located in the uppermost row of buttons. The display is controlled by a broadband scan converter (#2) and a 10 channel decoder (#3). The vertical display is a dedicated RBDE scope usually displaying adjacent airspace selectable via a rotary switch. Each scope could display radar data from only one site.  

1. Frequency selection panels. Each toggle switch corresponds to a discrete frequency. (VHF/UHF paired in some cases) The upper set of switches control where you'd like the output, speaker (up), off (center) or headset (down). The bottom switches toggle that particular frequency on or off at that control position.

2. Scan converter. Controls the display of the PVD in broadband mode (analog).

3. Ten channel decoder. The decoder offered 10 preset codes of the 64 then available (aircraft had 4096, and we were required to speak four digits, but the equipment could only read the first two digits) You could choose to display single-slash: "/" double slash: "//" or none.

The high altitude sector would display 21 as double (his traffic) and code 11 as single. the underlying low sector would display 10 as double and 11 as single.

So for a high altitude arrival you would say, "squawk 1100, descend and maintain FL240, report leaving FL270 (or whatever was clear of your traffic)."

Then you called the low sector, or if the room was laid out properly, you leaned over to his display, "Handoff, 30W of BVL, is AAL525, at FL290 direct SLC".

When the aircraft made the necessary report, you issues a change of frequency clearance to the low sector.

The low controller would say. "Descend and maintain 12,000, SLC altimeter 2995; leaving FL240, squawk 1000" and he'd disappear from the high display.

4. Scan converter for vertical RBDE scope.

5. Bell 300 telephone switching system (electromechanical). Provided intercom and interphone communications within and between FAA facilities. All control positions had multiple 6 button bays of buttons for quick access to different positions. A keypad was also provided to dial any other position that didn't have a quick access button assigned. The "R" position had this panel above the scope, the "D" and "A" were located below the strip bays.

PVD Key and Button Placement

This is the display of the DSR system. It replaced the CDC/PVDs.
Note that it emulates the key and button
placement (soft keys) of the PVD hardware.

       Additional information about each display provided below

The Radar Bright Display Equipment (RBDE) was used for about 12 years at  the facility. It displayed broadband radar data, which showed the  reconstituted raw PPI (Plan Position Indicator) intensity information  from only one radar site. These PPI displays (vector based) could not  store the screen image from sweep to sweep except in the screen phosphor  afterglow.

The RBDE video map looked like it was drawn by a crazy five year old  with a green crayon. The video map alignment was confirmed by at least  two permanent echoes aligned with a couple of "carets" displayed on the map. This display was nothing more than a glorified raster scan TV, but a big improvement over the PPI display.

The Plan View Display (PVD) replaced the RBDE scopes and  was a quantum leap forward and heralded the beginning of Radar Data Processing. The PVD was the first ALL DIGITAL radar scope. These displays were used continuously for another 25 years. These two generations of displays comprised 37 years of scopes at ZLC and are shown on the same web page due to the ability of both to display  broadband data.

The PVD could be used to display either analog broadband  (still controlled by the 10 channel decoder and scan converter) or  digital narrowband (RDP); the input selected by a single switch on the display. In the narrowband mode, all of the radar site data from multiple sites was mosaiced and shown on that display, regardless of  range.

We routinely had to revert to broadband on mids, planned  shut-downs and those pesky system crashes and starovers, a major Charlie  Foxtrot. These events were received with expletives being heard  throughout the facility. You never knew if it was a momentary hiccup or a  long term outage. Read the article "Broad Band Blues" from Flying Magazine 1980 for a good perspective.
These moments always seemed to happen during "pushes"  when the systems were put to high demand stresses. We wrestled the PVDs  horizontal and started grabbing shrimp boats and grease pencils for  target identification. These crashes were one of the most stressful and  scary moments in any controllers' career.

I used the back-up broadband on a PVD for six years until the installation (1981) of the Direct Access Radar Chanel (DARC), another Raytheon product. Finally, an acceptable backup in digital format. This  system still required us to drop the scope to horizontal and use boats  for target ID. It was still a one radar site per scope but it did  display the discrete beacon code and altitude. Later versions of DARC  solved these limitations but that story is beyond the scope of this  page.

Broadband was great for the display of precip but little  else. We routinely switched back and forth, between fat and skinny band  to see "weather" during thunderstorm season. Broadband stayed around  for a few more years and was finally removed from the facility, becoming  obsolete by newer technology.

Scroll down to the photographs for additional information. See also: Big Iron and CDC

Administrators Note: The story below demonstrates that even wacky ideas were tried in the field during the early days of RADAR.

An interesting story from Dick Arner, ZLC alumnus.
"At  ZID in 55 & 56 the CAA was just beginning center radar (tech &  eval) and used white tables with a radar projection from the ceiling.  Airways were marked on the tables by painted lines and in the 2 radars  we had (I think IND & HUF Terre Haute) there was quite an overlap  problem with double images! The shrimp boats were metal with a paper  insert and on one end the controller dialed the assigned altitude on a  rotary wheel."

Raytheon RBDE c1962 - 1974

       Radar Bright Display Equipment

RBDE-4 ZLC c1962

Glen  Molyneux at a control position. This display was controlled by a "10  channel decoder" and "scan converter" in the upper right corner of this  picture. I was on Glen's crew when I started my career in 1975.

Each scope could only display data from ONE radar site at a time. The other display was normally configured for adjacent airspace. Note the shrimp boats for target ID.

RBDE Display - Site Unknown
Do you know why there are two rulers sitting on this display? They are  actually used to measure distance, and when the range is changed, a ruler  calibrated to that range must be used. At ZLC our airways were mapped with 5 mile dashes on the Victor airways  and 10 mile dashes on the Jet airways. This system worked quite well and  we seldom needed to measure.

ZLC RBDE-4 Display c1962

If you  were an alumnus of ZLC then you know that the vertical display is showing data from the Francis Peak radar site, clearly indicated by the UTTR map.

The horizontal display (21 inch diameter), with shrimp boats, is  probably working SLC arrivals and departures to the south, and  configured to show data from the Cedar City radar site.

I believe this display  to be a "-4" scope due to the fact that it does not have the "joysticks"  of the RBDE-5 model. If you have additional information about these  displays please send them to us for posting.

RBDE-5 - ZAU c1963

This display is an RBDE-5. Note the obvious addition of the "joystick." From an ergonomic standpoint, I think it was too tall and in a poor place for usability. Ken Kerr advised me that ZLC never received "-5" scopes.

The joy stick permits controllers to  superimpose an electronic circle over any specific radar target. By  activating a switch built into the joy stick, the aircraft's transponder  code number appears on the beacon control panel adjacent to the  controller’s display.

Source: Screen grab from:

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