T. A. Gardner
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Here's a bit more on early SAM's and ECM. While the cite specifically discusses the Nike Ajax, this would apply to any of the SAM systems of the late 1950's into the mid 60's at a minimum. I'll include the citation first, then discuss this is an broader context.
www.goodreads.com
(It's Vol 2 in a 3 volume set)
Anyway...
All of these early SAMs relied on electronic analog computers to do the calculations and guide their missiles. The low data rates they could process meant that inputs from guidance radars and such had to be smoothed before being sent to the computer. The time required to do this process was on the level of several seconds per iteration.
What the ECM engineers and techs figured out was that if you jammed the radar within that cycle it could never produce the necessary data and the computer would fail to continue to control the missile sending it wildly out-of-control. Noise jamming, range or velocity gate stealing, etc., were all effective methods for doing this and only had to be repeated every few seconds within the data time loop of the missile system. For Nike Ajax, this was about 7 seconds.
Chaff might be effective, but almost every SAM system used Doppler shift electronics in their radars so it would be less useful than actively jamming the system. By the mid-60's computers had advanced sufficiently to shorten this loop to a point where simply jamming the signal intermittently would no longer work.
With Nike Ajax, one advantage was it used monopulse radars rather than conical scan. CS types were far, far, easier to jam and the SA-2 used CS in most of its models. This didn't make either unjammable, but rather just made Nike harder to jam.
In Vietnam, such tactics were very effective against the SA-2 because it was a late 50's design and used a very simple computer system. The Russian response was to add a television tracking camera to the radar to allow the operator to use an MCLOS back up to try and guide the missile to its target. This proved, as previous tests and attempts to build such systems had, ineffective as the operator couldn't accurately steer a missile by hand going at supersonic speeds miles from the control station to a speck in the sky.
The History of U. S. Electronic Warfare, Vol. 2: The Re…
For those who have a professional interest in electroni…
(It's Vol 2 in a 3 volume set)
Anyway...
All of these early SAMs relied on electronic analog computers to do the calculations and guide their missiles. The low data rates they could process meant that inputs from guidance radars and such had to be smoothed before being sent to the computer. The time required to do this process was on the level of several seconds per iteration.
What the ECM engineers and techs figured out was that if you jammed the radar within that cycle it could never produce the necessary data and the computer would fail to continue to control the missile sending it wildly out-of-control. Noise jamming, range or velocity gate stealing, etc., were all effective methods for doing this and only had to be repeated every few seconds within the data time loop of the missile system. For Nike Ajax, this was about 7 seconds.
Chaff might be effective, but almost every SAM system used Doppler shift electronics in their radars so it would be less useful than actively jamming the system. By the mid-60's computers had advanced sufficiently to shorten this loop to a point where simply jamming the signal intermittently would no longer work.
With Nike Ajax, one advantage was it used monopulse radars rather than conical scan. CS types were far, far, easier to jam and the SA-2 used CS in most of its models. This didn't make either unjammable, but rather just made Nike harder to jam.
In Vietnam, such tactics were very effective against the SA-2 because it was a late 50's design and used a very simple computer system. The Russian response was to add a television tracking camera to the radar to allow the operator to use an MCLOS back up to try and guide the missile to its target. This proved, as previous tests and attempts to build such systems had, ineffective as the operator couldn't accurately steer a missile by hand going at supersonic speeds miles from the control station to a speck in the sky.
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