View Full Version : FGR2 Radar Question
Fonsini
29th Jul 2015, 04:38
As eager and very spotty youths the members of my Aero Club were treated to a day at Coningsby back in the 1978/79ish timeframe.
As we were shown around the maintenance hangar, and after having been scowled at for poking our noses inside an ECM Canberra that had made a wheels up landing with remarkably little belly damage (on grass ?) we stood ogling the radar of a Phantom that was in the buff and minus the radome as it ran through some sort of ground test sequence. The antenna scanned from left to right in the traditional mechanical sweeping motion and then abruptly stopped in one spot and began to rotate - the small pointed transmitter array itself in the middle of the parabolic dish, not the dish itself.
I was reminded of this event many years later when a buddy of mine who happened to be a former F-15E WSO recounted the story of a technician who walked in front of a ground test of the APG-XX and received a lifetime dose of radiation. Now I'm sure this unit wasn't actually emitting anything but I always wondered what mode it was in when the dish stopped scanning and the emitter/antenna began twirling around - lock on mode maybe ?
Anyone know?
BEagle
29th Jul 2015, 08:35
What you observed was feed horn nutation, indicating that the MCS was locked.
Courtney Mil will probably be able to explain the theory of feed horn nutation.....;)
ricardian
29th Jul 2015, 08:47
Interesting wiki article that's worth reading (https://en.wikipedia.org/wiki/Conical_scanning)
Fonsini
29th Jul 2015, 18:45
Great info thanks guys, and a special thank you to the MOD project manager for the AWG series in UK Phantoms who was kind enough to PM me with specifics. The amount of knowledge in this website is humbling.
I had to wait 35 years for it not to be an OPSEC question, but I finally know what the radar was actually doing that day.
Now, if only it could reverse the aging process.
I'm afraid that after raster scan and the introduction of digital processing/ conical scan and Fast Fourier Transformations it all entered the world of, to quote a QWI, FM/WMM.....
Not to forget FMICW....F% €k Me It Can't Work, the outstanding weather radar on the glorious F2.....
Courtney Mil
30th Jul 2015, 09:00
Sorry, I'm a bit late to the party here. Ricardian's link is one of the simplest explanations of con scan I've seen in a long time. :ok:
johnfairr
30th Jul 2015, 18:47
According to Capt Bob de Vere, USMC, what was happening was "IFM".
Upon questioning him it transpired that IFM = "It's Fecking Magic", though in a US accent . . . . ;);)
PS, Bob was an exchange back-seater on 228 OCU 1973-75ish, and a very fine chap!!
NutLoose
30th Jul 2015, 19:59
We took one of our then new Chinooks down to the open day at what was then Fleetlands and they had a Phantom in one of the sheds on display with the radome open so Joe Public could see the radar, they had then placed a sign beside it saying Do Not Photograph The Radar... One did wonder which bright spark thought that was a good idea.
glad rag
30th Jul 2015, 20:42
Sorry, I'm a bit late to the party here. Ricardian's link is one of the simplest explanations of con scan I've seen in a long time. :ok:
Always used to wonder [but had a bit of an idea why] those scanners did that in the wee sma', damp hours at leuchars, an mcs fetish I believe...
Many years later, being assimilated into the dark side, at No2 SofTT [spits, a bit difficult to dodge THE question, when there's only three of you, lol], on OWS [short] Foxhunter course [can't remember that much of it tbh, the weeks "melded" together]...
...however one thing that struck me was the physical simplicity of mono-pulse tracking,..
..it took a real genius to visualise it however, imagine proving that mathematically on paper with a HB pencil, logtables and a rubber...
Utterly Incredible.
Fox3WheresMyBanana
30th Jul 2015, 20:51
As Blackadder said
Lots of very clever, very dull men, looking at machinery
glad rag
30th Jul 2015, 21:04
And it has always been thus! :D
Fox3WheresMyBanana
30th Jul 2015, 22:23
I recall an after-hours tour of Rolls Royce Derby for the Institute of Physics, guided by a retired chap who'd been working on jet engines since 1943 (and was almost completely deaf to prove it!).
You can get into a lot of detail, and hear some remarkable stories, when everybody
1) Asks intelligent questions, and
2) Listens to and understands the answers.
I also heard Ken Wallis (RIP) speak at Boscombe Down; another truly remarkable man.