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Comments on SAGE Jamming Resistance

There are many jokes beginning with
  "Be careful what you ask for,
    you might get it !!"

I was invited to join an Air Force

which was very kind as I was Army  ;-)
  worse yet, our mission was to shoot down aircraft
    hopefully Soviet aircraft at the time.

Trying to respond to vague acusations here in California that 
  "SAGE was no good", 
I asked the Air Force Radar Station veterans of the above group
what capability SAGE radar inputs had against jamming.

That was almost a mistake, 
as I got what I asked for :-((    ;-))
    Lots and lots of information and comments  ;-))
Contributors (e-mail address not included) (In chronological order) were:
1) David E. Casteel, Captain, USAF (ret)
      Former Radar Maintenance Officer and SAGE Computer Maintenance Officer
2) William Mitchell, Tsgt Ret
3) Don Helgeson, 635, 751, 757 152TAC
4) Ed Elkins, RICMT/AJO 27372/27672 ... Thule,12 MWS 70-71
5) Dick Waddell
6) Leon C. Gall, Former A/3c USAF
7) Robert A. Shaffer, Charleston SC, 792nd Radron
8) Tim Peters
9) Gary.J.Wozniak, FAA
10) Jerry Fowler

"Executive Summary" the flood as follows:
a) The Air Force took anti-jamming very seriously
b) No response was specific enough to risk giving the show away
- (There is of course a constant contest "Measure vs CounterMeasure")

More detailed summary -

( This is a much bigger job than I "bargained" for.
Think I will back off for a while. )


"Raw Material"

from David E. Casteel Captain, USAF (ret) Former Radar Maintenance Officer and SAGE Computer Maintenance Officer
also see his Recollections of the SAGE System
the main thrust at attempting to defeat jamming of the SAGE system was not at the computer level (at the Direction Center) but prior to input to the computers (at the radar equipment). Virtually all search radars in use by ADC had at least some rudimentary fixes designed to reject jamming, but admittedly the older units did not have much. The later FD (Frequency Diversity) radars--AN/FPS-24, AN/FPS-27, AN/FPS-28, and AN/FPS-35 were developed to spread the frequency coverage widely and thus make simultaneous jamming of adjacent sites more difficult; these radars also had receivers with sophisticated anti-jam circuits. The AN/GLA-8 units also supplied with those radars allowed for complex gating and combination of the various fixes into a set of alternate composite video streams. The best of these was then selected to be sent to the AN/FST-2B Coordinate Data Transmission Set to be digitized and sent to the inputs of the AN/FSQ-7 computer at the Direction Center. There was provision for 2 such channels so 2 different composites could be sent forward for selection by the DC.

I left the ADC SAGE environment in 1964 and did not get to observe how well (or poorly) these elements handled sophisticated jamming activities. I understand that many of the better features were either disabled or not utilized because of maintenence problems with them or because FAA (a joint user of the ADC radars) did not like the video outputs. (From my viewpoint, FAA should not have had any say in the matter--those decisions should have been entirely within ADC's discretion--but I wasn't in control. FAA could have lived with what ADC considered useful or built their own sites.)

Even though I left SAGE in 1964, I did not leave USAF and I stayed in touch with some folks who were still in SAGE. I understand that the SDC programmers (and later Blue Suit ones) were working on isolating the jamming strobes that got through the anti-jam circuits and attempted to extract aircraft position from the intersections of them. Presumably the fact that different sites would have different sets of strobes generated by the same aircraft would have made it possible to narrow down the possible intersection points. (I am not clever enough to know how this was done or even if it were possible.)

The function you mentioned about determining the center of a target blip was actually one of the principal functions of the AN/FST-2B and it had nothing to do with ECCM. It continuously examined 16 consecutive radar sweeps in a moving window and statistically evaluated where the start and end of a blip occurred, and determined the center of that blip. I have described that process in earlier posts so won't go into it again here.

from William Mitchell, Tsgt Ret
I was a ECCMT (Electronic Counter Counter Measures Tech) and the SAGE defense against Jamming was at the Radar Station.

It was our Job to keep a clean Scope so a clear picture was presented to the Combat team at the SAGE Level.

There was many different measures one could take to present a Clean Air Picture. The first step was to ID the type ECM the site was receiving and knowing what steps to counter it. To be able to be effective an ECCMT had not only to know the type of ECM, But what ECCM His radar set had to counter the many types of ECM. There was times that a Radar station would become saturated and could no longer present a clear picture. This happen, but not often. If it did happen, other Radar Stations could pick up that area so that SAGE would not be Saturated.

I worked on the FPS-27 and it was excellent Radar to counter ECM and even tho I never worked on the FPS-24, I understood it was even better.

from Don Helgeson, 635, 751, 757 152TAC
When we were jammed I always wondered why the operation's folks would not let us reduce our 'FPS-3's sensitivity to get a good azimuth strobe at Mt. Laguna in the mid 1950's. We did have some fun with the SAC folks by setting our ('FPS-8) GPS-4 frequency right next to the '3 and then moving it away. Later when working with the MSM -11 SAGE radar test set out East we were able to help find a local source of interference. There seemed to be no interest in ADC in those days about equipping radar sites with the simplest means to go out and nullify a local jamming signal.

On another note a K-33 Autocar truck chassis that was used for the SCR-270 radar set has turned up in CO. It would be nice if someone could manage to spot one of the York-Hoover van bodies the were used on it.

Now if this sounds farfetched consider this - in 1988 the Historical Electronics Museum had given up looking for an SCR-270 antenna. When I told them that I had located one up in Saskatoon at the Univ. of Saskatchewan they refused to believe me until I forwarded pictures that Dr. Don Koehler sent me a few weeks later. The restored AN-140 antenna mounted on its K-64 trailer was the centerpiece of the 50th anniversary celebration of the Pearl Harbor attack that the HEM staged in Baltimore in December of 1991. The USAF did not even think of preserving a BC-304 A scope from the '270 (And still doesn't.) A little earlier Mindy Rosewitz the curator of the C&E Museum at Ft. Monmouth had as a visitor that happened to mention a pile of vintage electronic equipment in the corner of an old factory building in Patterson, NJ that he had bought. She followed up on that tip and lo and behold there were several BC-403 scopes and BC-404 receivers in that pile that were restored for 50th too.

from Ed Elkins, RICMT/AJO 27372/27672 ... Thule,12 MWS 70-71
Since I was stationed at both a SAGE Direction Center and several Radar sites(Pt.Arena & Keno) including BMEWS(12MWS Thule), thought I would throw in my 2cents worth on this subject. At the Direction Center, the Electronic Warfare officer was known as the RICMO (Radar Inputs Counter Measures Officer). His tech was the RICMT. I performed the RICMT job for 5 years while stationed at Adair AFS, Or. (POADS/26th AD). In the begining,1963, we had 5 RADAR sites feeding info to us, and when in I left in 1968 there were 13. During normal hours, we monitored the inputs from the sites and made sure they were operating and within specs. During missions, we recommended to the sites what electronic counter-measures to take to reduce (change receivers/frequencies) the electronic jamming from the attacking Faker)aircraft. We had other duties,such as maintaining status boards, making sure P.M.'s were taken as scheduled, assisting the Air Surveillance section if they were shorthanded.

In the Air Surveillance Branch at the D.C., they also had what was called a Passive Tracking section. You did not view the radar data, but geometric lines that intersected in the predicted area of the jamming A/C. The computer (Clyde) would receive the jamming strobes from the radar sites and as they intersected, it would predict the approximate location of the A/C. If my memory serves me I think this was the last resort in the SAGE system.

At the RADAR sites, we were called AJO's (Anti-Jamming Operators). At the initiation of increased Defcon or simulated conditions, the AJO would dial up a number and be connected on a conference call with other sites and the RICMO/RICMT. At this time the RICMO controlled the RADAR sites and communicated what changes he wanted the AJO to implement to decrease the interference to the radar receivers. I worked with the FPS24, FPS-67, FPS-90, FPS-26 and the BMEWS radars. At the sites, we also had additional responsibility of manning the Dial Restoratio Panel (switchboard).

Our main bible was ADCM 55-44, which listed all the features of all the RADARS in ADC. I believe it was 5 or 7 volumes about 3 inches thick each. When WAPS came into being, that is what all the 276xx were tested on. There were a lot of cross trainees in 64-68, and by 1972 the field for promotions was almost nil above Ssgt..

I can go on, but am sure most of you are tired of reading or bored.

from Dick Waddell
They might have gone outside the ECCM box and developed HOJ (Home on Jam) interceptor missiles.

from Leon C. Gall
I think HOJ was a subset mission for the SHRIKE but was never needed.

from Robert A. Shaffer, Charleston SC, 792nd Radron
Edward Elkins hit the nail right on the head. That was an excellent description of the ECCM ( Electronic Counter Counter Measures ) functional positions at the various segments of the Radar Air Defense system. I have not seen it expressed any better and I spent ten years of my AF Career performing those duties. I got some real hands on application at the 615th AC& W SQ in Birkenfeld Germany where we could observe the East German AF and the Soviets fill up the Berlin Air Corridors with chaff and in one fell swoop we could functionally eliminate their efforts and watch the traffic proceed unobstructed. Thanks Ed, you rekindled some good memories.

from Ed Elkins, RICMT/AJO 27372/27672 ... Thule,12 MWS 70-71
Robert: thanks for the kind words. Figured we had so many individuals in the group that had never seen a RADAR scope i would give a brief description of what one of the jobs entailed.There were many, all with different important functions vital to Air Defense.

In 1962 as a one striper at Keesler I came close to getting stationed in Germany. Came down with tonsillitis,got backlogged for a week in the hospital on water and APC's, and got stuck in another class. My roomate and all of the original class I was in went to Syracuse for 412L school then to Germany. I came to Oregon. Have been here since 1973.

BTW, I also had 5 years in a TAC TACC in the Oregon ANG.

from Tim Peters
Ed, Enjoyed your post as I'd been racking my brains trying to remember the counter-measures used for jamming in the SAGE system. I now remember being on the Passive Tracking Team before I went back to the Height Section at Adair. While assigned to the Radar Eval Squadron at Hill we TDY'd to Hawaii to eval the ROCC's Passive Tracking system and it didn't appear that the system had changed much.

from Gary.J.Wozniak, FAA
Hi Dave, While you are correct in saying the FAA did not care about AJ functions, it was not because of maintenance problems. No ECCM radar functions were "turned off". They were always there if needed. In the case of the -27's the Automatic receiver selection (ARS) boards were still functional. Log receivers still work normally, they just saturate from the output back to prevent loss of signal. Dickie Fix is passive until a barage of noise is injected into the front end, wide band or narrow band Dickie Fix. The FAA mission was/is quite different from the AF mission of the '60/70's. At joint use sites where FAA was paying the bills, they maintained only what they needed for flight plan verification. The FAA tracks Large aircraft, the Air Force wanted to track small aircraft and evaluated radar performance on a 3db basis. As the defense concept changed when the Air Force realized the requirement of directing intercepts over Kansas was nil, they started closing inland sites working their way out to the coasts. Meanwhile, the FAA WAS building their own sites to make up for the loss of "rented" Air Force data. Now, after 9/11, the situation is quite different, with the FAA having the sites and the Air Force wanting the data. Just like the funding that made those origional 7 astronauts go up, that is also what turns the radar antenna. Lots going on behind the scenes,

from Jerry Fowler
Well the AF in the latter 60's (68-69) did on the FD radars anyway, (read 24 & 27). The AJ features on those systems were just 'on' 24/7. In the case of the 24 if the HLPC didn't take it out nothing else was going to. In 74 when the 27A came out CPACS was the name of the game. Just after the Havre MT system was upgraded a gaggle of big wigs know it alls came out to evaluate some new jamming system. I was in OPS and happened to over hear the big guy comment that he just couldn't understand why nothing was happening, it was like we had CPACS on the radar. I told him it did since the mod, they all packed up and went home PDQ! Figured, the left hand don't talk to the right hand.