Technical Info

The primary search radar for DEWLine sites in Canada and Alaska was the AN/FPS-19. It was a magnetron type radar made by Raytheon. The AN/FPS-19 was a high power L-Band search radar consisting of two identical radar sets feeding a dual (back to back) antenna. Peak Power was 137 Kilowatts and Average Power 400 Watts. The Pulse Repetition Frequency (PRF) was 400HZ and Pulse Repetition Time (PRT) 2500 microseconds (µsec). Pulse Width (PW) was 6 µsec. and the Duty Cycle 0.0024.

Paul Kelley monitoring the AN/FPS-19 radar in the radar room at FOX Main. Note some of the automatic alarm gates on the right. Circa 1962.

The two antennas, placed back-to-back, created a double lobe (high and low angle coverage). Similarly, the two 12 inch PPI indicators offered a display of 360 degrees in azimuth, extending to a range of 160 nautical miles. The operator might select by manual control, range displays of 20, 40, 80, or 160 miles. The expanded “A” scope, in turn, covered a distance of 10 miles over 5 inches of display.

The automatic alarm of each radar consisted of 36 range gates, in groups of 6 guard bands, each of the latter covering an interval of 90 microseconds or a distance of 7.5 nautical miles. Any target appearing in either of these bands activated an audio alarm. Further, the gate alarm automatically tripped a scope camera which photographed the indicator for one complete sweep, thus giving a permanent record of the target.

In the late 1980’s, the AN/FPS-19’s were replaced by the “state of the art” AN/FPS-117 at those sites that became part of the North Warning System (NWS). The AN/FPS-117 was built by GE.

The primary search radar for the DEWLine sites in Greenland was the AN/FPS-30. Bendix built this long-range DEW-Line search radar that was originally termed the “Sentinel” radar. Once planned as a replacement for all AN/FPS-19 DEWLine radars, theAN/FPS-30 was installed in 1961 only at the four Greenland “DYE” radar stations. It operated at 570 to 630 MHz. Its peak power was 150 kW, and its average power was 3 kW. The AN/FPS-30 radar’s pulse-repetition frequency (PRF) was 500 pulses/sec., and the antenna aperture was 45 ft. x 25 ft. The transmitter output tube was a Klyston with 62-dB gain (this Klystron power amplifier was later adapted for the Raytheon-built AN/FPS-28 frequency-diversity air-defence search radar).

The AN/FPS-23 continuous wave “fluttar” (Doppler Effect) radar system was manufactured by Motorola, and operated at frequencies between 475 and 525 MHz, with 1 kilowatt of output power. AN/FPS-23 radars were continuous-wave (CW) systems that

AN/FPT-4 transmitter at CAM-D. One of four. Two faced east towards CAM-4 and two faced west towards CAM-3.

were comprised of geographically-separated AN/FPT-4 Fluttar Transmitters and AN/FPR-2 Fluttar Receivers. AN/FPT-4 Fluttar Transmitters were located only at Intermediate (“I”) Sites, while AN/FPR-2 Fluttar Receivers were located only at Main and Auxiliary Sites. The transmitters and receivers were typically about fifty miles apart. The function of this Doppler-effect detection system was to fill the low-altitude gaps between AN/FPS-19 radars located at Main and Auxiliary DEWLine Sites.

Designed to detect aircraft crossing at low altitude (50 feet over water), the dual-feed antenna system introduced signals through a series of audio filters. The latter then passed the frequencies which corresponded to the doppler frequency produced by the intruding aircraft. Targets from Fluttar receivers were finally recorded on magnetic tape and displayed on a strip recorder at the console for the console operator to analyze.

By Brian Jeffrey
Each Main and Auxiliary station had four (two-main and two-standby) Collins Model 243F3 VHF transmitters for use on the general aviation frequencies of 122.2 MHz and 121.5 MHz (the emergency frequency) and were used to communicate with commercial aviation aircraft. The matching VHF receivers were Collins 51M7’s. There were also four (two-main and two-standby)  UHF air/ground radios, the AN/GRT-3 transmitter, for communicating with military and SAC aircraft on 236.6 MHz as well as monitoring the military emergency frequency of 243 MHz. The matching UHF receivers were AN/URR-35D’s.

The Immediate sites (I-Sites) had a Gonset Communicator air/ground transceiver for communicating with incoming aircraft, usually the Lateral flight from one of the Main stations bringing mail and supplies.

By Paul Kelley
A pair of Collins 51N2B receivers was installed in the Receiver Room at each Main and Aux site. One was tuned to 3023.5 kc – a standard air-to-ground frequency. As I was to discover later, this was a holdover from the earlier days of aviation and most aircraft now used the VHF frequencies. I don’t recall ever hearing anything on this frequency during the 15 months I was on the Line.

If a voice transmission was received on 3023.5 kc the only means of responding would have been by voice modulating the AN/FRT-37 Low Frequency beacon.

The second 51N2B was used to monitor the international HF emergency frequency – 5295 kc.

By Brian Jeffrey
Located in the Recreation Modules, far from the Electronic Modules, was a small room containing the station’s Emergency Radio System which was to be used case of a dire emergency such as a fire or other disaster that wouldn’t allow the use of the main communicatiuons systems in the Electronic Modules.

The system consisted of a Collins 431-B1, 1000 watt, transmitter and a Collins 75A4, HF receiver, connected to a three-element beam antenna that was generally frozen in a southerly direction.

The system was available to any licensed amateur radio operator and many hours were spent arranging phone patches with amateur operator in the south for station personnel so that they could talk to their families.

by Paul Kelley
Each site had a Marconi TR100/6, 100 watt transceiver tuned to the 5295 kc HF emergency frequency. On each site the unit was located in the garage, a good distance from the main modules, together with a stand-alone diesel powered generator. It was referred to as the Disaster Radio System as it was the last resort in the event that everything else had failed for whatever reason.

For those sites with access to open water in the brief arctic summer. the system was also used during what was known as the sealift – the restocking of such sites with bulk materiel via ship. On these occasions the TR100 was switched to 2716 kc – a standard harbour control frequency – for ship-to-shore communications.

Other than testing it periodically these were the only occasions it was exercised while I was there. Happily, there was never a disaster during my time on site.

LF Beacons at the AUX Sites were the AN/FRT-37’s (Wilcox-99C) which had a power output of 50 Watts. At the “I” Sites, the beacon was an ABT-23 and the power output is believed to be 35 Watts.

By Clive Beckmann
Initially, the DEWLine’s tropospheric scatter lateral (east to west) communication system in Canada and Alaska initially used the AN/FRC-45 produced by Collins Radio Corp. The AN/FRC-45 used “dual diversity” which made it subject to fading as atmospheric conditions changed so it was upgraded by the “Surestop I and Surestop II” programs. The new equipment was produced by Radio Engineering Labs (REL). The resulting equipment in Canada was named the AN/FRC-102. The fading problem was overcome by the use of “quad diversity”. In Greenland, the AN/FRC-39 was used. The AN/FRC-102 and AN/FRC-39 were both based on the MRC-98 exciters and parametric amps, the difference between the two being based on the choice of High Power Amps and multiplexer systems.

By Clive Beckmann
On the I-sites, the method of communication with the adjacent Auxillary or Main sites was via VHF Mobile Radios. I believe the original configuration was a commercial General Electric VO-38 radio that provided 50 watts of power. Since VHF radio is line-of-sight (LOS), this power level wouldn’t always provide dependable communications. Consequently, the systems were beefed up by the addition of 250 watt power amplifiers. This became known as the Miscom system (short for Miscellaneous Communications). This upgrade apparently provided satisfactory communications until deactivation of the I-sites. All the GE radios and the 250 watt amps were retrieved from the Alaskan sites and stored in the Oliktok (Pow-2) hangar after deactivation where they gathered dust for several years. During the winter of ’66, they were deemed to be excess assets and were hauled about half a mile out onto the ice. At spring thaw they sank to Davey Jones’ locker, their final resting place.

By Clive Beckmann
The original DEWline rearward communications design used the IS-101 Ionoscatter Radio system (AN/FRC-101). This was a data-only system that could not provide voice grade circuits. Teletype channels were routed over this system to sites at Age-X (Anchorage), Nel-X (Ft Nelson BC, Canada) and Res-X (Resolution Island NWT, Canada on the east coast). Of course, the primary function was to provide surveillance date (aircraft movements) to military authority in the lower-48. This system used huge curtain antennae which were maintenance intensive. Because of the drawbacks of the IS-101 it was replaced in Alaska in the early ’60s by newly-installed tropo links between Barter Island and Ft. Yukon, and between Ft. Yukon and Pedro Dome outside of Fairbanks. At the time of activation of the Barter/Yukon 50 Kilowatt shot, it was one of the longest in the world at over 200 miles. Later on the Hall Beach (Fox Main, Canada) shot to P- mountain Greenland became the longest in the world at over 600 miles using 100 Kilowatt transmitters. IS-101’s were also installed at PIN M, CAM M, and FOX M

By Clive Beckmann
Surestop-I upgraded the old FRC-45 radios from Cape Dyer (DYE-M) to Cambridge Bay (CAM-M). Then, at a later date, Surestop-II continued the upgrade from CAM-M to Barter Island (BAR-M). This all happened prior to the big build-up in Viet Nam. Unfortunately, this military priority caused all the tropo radios being produced by Radio Engineering Labs (REL) to be siphoned off for shipment to the war zone. These radios were intended to be installed in Alaska as Surestop-III. Consequently, the Alaska DEW sites never had the old FRC-45 radios upgraded until the general upgrade in 1982-83 which replaced all tropo radios from LIZ-2 through DYE-5 and the NARS sites with a state-of-the-art REL system. Because the venerable FRC-45 provided marginal communications service during periods of heavy “fading”, a way was sought to provide better radios in the Alaskan sector. Someone came up with the bright idea of closing every other DEW site along the entire Line as a cost savings measure. A side benefit would be that the closed Canadian sites would each yield two Surestop terminals, enough to upgrade all the Alaskan sites. So FOX-1 was the first site designated for closure, along with POW-3. The Fox-1 radios were installed on the BAR-M west link and the POW-2 east link, thereby allowing closure of POW-3. This program was discontinued after FOX-1/POW-3 and I’ve never seen an official document that stated the reason why. I’ve heard rumors that some environmental entity had insisted that the closed sites be restored to pristine condition, meaning complete removal of all construction, leaving only gravel pads surrounded by tundra. This was projected to be so expensive that the Government decided it would be far cheaper to fund all existing sites for continued operation rather than continue to shut them down for cost savings.

By Clive Beckmann
This was the LF communications system that ensured that Strategic Air Command (SAC) aircraft could be contacted in an environment that included nuclear detonations (which could render HF/VHF/UHF frequencies unusable). The equipment was located in SAC aircraft and at selected ground stations, including all Main DEW sites. As memory serves, SLFCS operated in the 20kHZ to 50kHZ band. Communication was one-way, i.e., SAC transmitted the messages and they printed out at the receive locations on a printer. The printers were known as the “thumpers” as the line feeds were loud enough to wake up the dead! Remote locations could not answer back. When DEW sites received traffic, the console operator would read the message (which was, 98% of the time, a test message that exercised the equipment) and acknowledged receipt by an entry in the console log. But sometimes actual SAC traffic would come in. When this happened, the console operator would immediately re-broadcast the traffic verbatim on both UHF frequencies (236.6 and 243.0 MHZ in AK). The SLFCS antenna was comprised of two large “loops” (about three feet in diameter) that were arranged 90 degrees to one another on the same axis. It was known as the “orange peel” antenna (kind of looked like a peeled orange and was orange in color) and sat outside on the ground near the surveillance room.

By Clive Beckmann
This system was comprised of the land-line comm network that connected the SAC Command Post (Offutt AFB, Omaha) with the remote UHF sites, which included all Main sites in AK and Canada; the Greenpine switching console (located next to the DEW control consoles); and included the two UHF radios (236.6 and 243.0 MHZ in AK) installed at the DEW sites. The system also included the radio links between the SAC Airborne Command Post (Looking Glass) that somehow tied into the communication system that terminated at the DEW sites as described above. When SAC wished to broadcast traffic via the remote sites they would contact all NRCCs (NORAD Regional Control Centers) and NCCs (NORAD Control Centers). In AK, the NRCC was the ANRCC (AK NORAD Regional Control Center) at Elmendorf AFB, Anchorage, and the NCC was Murphy Dome AFS, not far outside of Fairbanks. Murphy Dome would then do a switch action that completed a circuit to illuminate a red lamp and activate a warbling tone on the Greenpine switching console. The DEW console operator would use a special handset to answer, e.g., “Barter Island Greenpine”. If the SAC operator wished to broadcast traffic he would request “all operational frequencies,” and the DEW console operator would do switch actions to give control of the 236.6 and 243.0 A/G transmitters to SAC. Then SAC would key the transmitters and begin the traffic broadcast which always started with “Skyking, Skyking, message follows…”, and then the coded traffic. At the conclusion of the transmission, you would hear, “SAC out”, which was the DEW console operator’s signal to restore the equipment to normal. The Greenpine antenna was a vertical UHF array that was enclosed in a cylindrical fibreglass radome that was approximately 20 inches in diameter by 8 feet in length. At AK and Canadian sites these antennae were usually mounted atop a 60 foot telephone pole. Sometimes SAC would do a roll call of all Greenpine sites. It was interesting to hear all the sites polled and the respective operators answering because they were at locations around the world.

Much of this information has been “borrowed” from Larry Wilson’s excellent DEWLine website.