A.I.23 reflector size
 

For those who know... what was the diameter of the radar reflector dish in the Lightning?

One comment on a forum says 24", but I can't find an definitive statement in any on-line reference.

If I still worked at Crewe Toll, I could tell you - there used to be one on a stand in one of our staircase landings (there was a Blue Parrot on our floor, IIRC).

24 inches is at the upper end of "about right", but that's a decade-old memory. The best result for "AI.23 radar" on google images is from a spanish-language website, and to my dim memory it looks more like TFR (the TSR.2 set) than AI.23. IIRC the AI.23 was shaped to fit the intake and was more conical towards the rear, not cylindrical.

As ever, I apologise for my inaccuracies...

Edited to add, "found a link".

http://www.apss.org.uk/projects/APSS...edium/0001.jpg

Look at the size of that wave guide!!!

Softie, you do mean the horn don't you?

The waveguide at the horn is 4 wavegides in a rectangular array, to give the 'monopulse' error signal. The frequency was 10Ghz (3cm). Now AI17 (3GHz, 10 cm) - that had waveguides like drainpipes.

AI23 radar dish
 

The dish was in reality two parabolic reflectors joined along the vertical edge. It was a V clever arrangement; with the four-horn feed (split two to each half of the reflector) it transmitted (at 8,500MHz - 9,000MHz) four overlapping lobes which allowed the radar (unlike contemporary conical scan radars) to use sum and difference signals to angle track from a single pulse.

AI23 radar dish
 

I've just been up in the loft with a tape measure to find my dish:

dish width is ~53 cm / 21 in

dish height at the join between the 2 reflectors is ~48.5 cm / 19 in

The reason for the 2 halves is that although it was amplitude comparison monopulse in the vertical plane, it was phase comparison in the horizontal plane - the L-R feed horns thus needed to be about 3 ish wavelengths apart.

:ok:

Softie said: "Look at the size of that wave guide!!! "

I think you are looking at the trunking on the wall!!!!

Hmmm, someone who'd keep an AI23 dish in his loft AND be enthused enough to go and measure it...

Sounds like someone who spent (considerable) time teaching me and many others how to derive (from first principles of course) the radar range equation at the College of Knowledge...

Does the name Caracal mean anything to you...?

Thank you very much, radar101. You've been very helpful.

You as well, rhajaramjet.

Here is another view..

http://lh5.ggpht.com/_1BXJmcdgZEw/SQ...0/DSC_0276.JPG

note that in the above photo the dish is on its side

Was AI 23 the only version of AI used on the Lightning?

The reason I ask, in '64 I was working in the Akrotiri, Electronics Centre, I had the Green Satin bench. When 111 Sqdn came to chase away the Turkish AF F-100's we had an AI bench added to the Radar Bay. From my dim memories of it, it was not the same as the photo's that have been posted.

The one thing that I do remember was that there was great use of wire wraps in place of the soldered connections the rest of us worked with.

AI23 was on the F1/1A/2/T4

AI23b on the F3/F6/T5

They both looked pretty much alike unless you had to service them, and like the unit in the photos as far as I recall.

Yes, hundreds of wire wraps to connect the modules. More reliable than multi way connectors, but even with the electric wrap/unwrap tools time consuming. Strictly 'modified wire wrap' - the first turn on each end included the insulation.

AI 23 Variant
 

The only difference that I came across was in relation to "Computer white" and "Computer green" where one was the full intercept version for the UK Lightings as opposed to the Saudi Version. (So we were told):confused:

As for the wire wrap why the first turn to include the insulation? doing that would have failed the fitter course but my memory fails me as to ever seeing that at Wattisham.

BTW the old DEC PDP11 computers used that method of wrapping as well?

As I recall (and my AI23b course at Cosford was in 1965, so it's going back a bit) 23b had a number of extra features, plus data link which was never inplemented at the ground end so not used in practice.

The modified wire wrap prevented a weak point at the first few corners where the post deformed the wire. The 6 (?) turns of uninsulated wire gave 24 airtight contact points in theory. There was a long and boring Ferranti document relating to acceptable techniques.

And yes, 1970's vintage PDP8 @ PDP11 backplanes were wirewrap.

! 11-PDP a ni deppart m'I ! pleH

(Sorry - little-endian in-joke)

Herewith one genuine DEC issue wire wrap tool PDP-11 backplane's for the use of.

http://alisoncc.com/nwimages/wirewrap.jpg

IIRC, AI 23b added functions for the Red Top missile (beam and head-on firing) and there were some enhanced ECM facilities. These were in ‘computer red’; those features which were not applicable to Saudi Aircraft resulted in different ‘colour’ computers.
I am not sure if the Saudis bought the air-to-air unguided rocket-pack option (AI 23b function ? ), although they may have used them air-to-ground (not an AI function ? ); there may have been other changes due to the bombs fit etc.

For the era, AI 23 was a remarkably capable system with some very advanced features. The radar and the missiles had good capability in the then ECM environment, and overall, they had a very good ‘kill’ probability, better than comparable systems at the time and initially better than the UK Phantom fit, although the latter had a better radar (and a Nav).

Thanks for the answers about the AI23. It must not look right in my memory.

As for wire wraps in computers, I can't speak for the PDP kit but IBM 1400's, S/360, 1800 DACS and 1130's all used wire wraps. Lots and lots of 'em. :uhoh: