Birmingham Elmdon - 1970s 50cm radar

[Mooncrest]

Does anyone know the make and model of this radar ? I'm afraid I can't supply a picture but I saw it in a CAA brochure about Birmingham on the ATC WordPress site. I've never seen one like it before. If it helps, it was used concurrently with the Plessey ACR430.

Thankyou.

[HEATHROW DIRECTOR]

Marconi 264?

[chevvron]

Might even have been an S232. We had one at Farnborough until about '91 when we had Watchman Crown consoles installed which used fibre optics so the 232 wouldn't interface.

[Mooncrest]

Thankyou for your replies. It's not a Marconi 264 - I know what one of those looks like but I haven't seen a 232 before so that's a possibility. It's much the same shape as a Decca 424 but bigger and looks like it's made from yellow chicken wire.

[Jay Doubleyou]

If my memory serves me right, Birmingham had an S232 as far back as my FTU experience in 1964, I have no idea how long it lasted. Although the aerial was large, it was smaller than the 264, and had a more rounded top.

[Mooncrest]

I believe it is a Marconi 232. Odd-looking machine. Thankyou all.

[ZOOKER]

Definitely a Marconi S232 Mooncrest.

I remember it from a couple of spotting trips in the early 1970s. Very distinctive aerial shape.

Went on a liaison visit in the early '90s and I'm sure they also had a DECCA 424, or something similar.

I found some information on the S232.


Radar Basics - Marconi S232 (http://www.radartutorial.eu/19.kartei/11.ancient/karte076.en.html)

[Mooncrest]

Thankyou Zooker. It seems to have enjoyed a healthy service life, albeit not operational in the same numbers as the 264. The other radar at Birmingham back then was a Plessey ACR430 which itself is likely to have been preceded by a Decca 424. Leeds Bradford had a 424 then a 430 but never any 50cm radars. I believe it was quite common for UK airfields to have both a 10cm and 50cm radar concurrently. Jersey and Bristol spring to mind.

[chevvron]

Thankyou Zooker. It seems to have enjoyed a healthy service life, albeit not operational in the same numbers as the 264. The other radar at Birmingham back then was a Plessey ACR430 which itself is likely to have been preceded by a Decca 424. Leeds Bradford had a 424 then a 430 but never any 50cm radars. I believe it was quite common for UK airfields to have both a 10cm and 50cm radar concurrently. Jersey and Bristol spring to mind.

Glasgow had 2 x S264s when I was there in the '70s; no 10 cm.
Many RAF airfields relied on CADF to 'vector' the aircraft overhead and let down until they could be seen on either ACR 7 (424) or PAR to commence a talkdown, both of these being 3 cm so still not 10cm, the problem being 3cm radars are more affected by weather clutter than 10cm so need some sort of weather suppression. The RAF's latest PAR is processed which effectively suppresses all but the very heaviest rainfall. They can also display SSR.

[LookingForAJob]

...ACR 7 (424) or PAR to commence a talkdown, both of these being 10 cm.Don't know about PAR equipments but I think you'll find the 424 and 430 were both 3 cm wavelengths.

[chevvron]

Don't know about PAR equipments but I think you'll find the 424 and 430 were both 3 cm wavelengths.

Yeah what am I talking about; PARs and ACR7/424/430 are all 3 cm; I've amended my previous post.

[Bittell Lakes]

I can remember watching a DanAir 727 take off and head south on that radar. After a while, it disappeared, then reappeared. The controller said it had probably just accelerated through the radars (something?) speed, at which the radar couldn't see the traffic. The antenna was huge, about a quarter moon shape, painted red. About 10 rpm, I guess. The other, higher frequency radar was prone to show weather and was only used for SRAs or in case of unavailability of the main radar.

[Bittell Lakes]

Oh and those who lived within line of sight had a regular 'chirp' on their TV, every time the antenna pointed their way - nothing compared to having a pre-hushkit 1-11 low over your roof! At least it was nice soft sound - would be quite nice to hear either of those again.

[chevvron]

I can remember watching a DanAir 727 take off and head south on that radar. After a while, it disappeared, then reappeared. The controller said it had probably just accelerated through the radars (something?) speed, at which the radar couldn't see the traffic. The antenna was huge, about a quarter moon shape, painted red. About 10 rpm, I guess. The other, higher frequency radar was prone to show weather and was only used for SRAs or in case of unavailability of the main radar.

Probably 'blind' speed.
Difficult to explain but it's to do with the moving target indicator (MTI) which normally suppresses all non-moving objects. On 'simple' radars where the radar pulses are sent out at a regular rate, at some time the reflected pulse from the aircraft equals the emission of the next pulse, the MTI thinks the blip hasn't moved and cancels it.
On more recent radars (the S232 was designed in the early '50s) the pulse recurrence frequency (PRF) is staggered. On the 10 cm Plessey AR1 of early '60s vintage, the PRF 'stagger' was was in the ratio of 1.2.3 and the first blind speed was in excess of 1,000kts.

[Bittell Lakes]

Blind speed - yes, that'd be it.

[Jay Doubleyou]

On radars of that vintage there was also “tangential fade” where the target was on a tangent, i.e. always at a constant distance from the head even though it moved in azimuth.

[ZOOKER]

Somewhere in the loft is my CAA Radar Theory training manual, and all the notes from John Townsend's splendid lectures.

The Airbus 'Guppies' never suffered from tangential fade. Beam on, they always produced a huge primary return. It would be interesting to see an A388 on a raw primary display, I bet it would look similar.

[oldandbald]

I do remember that on the acr430 (3cm) on an SRA a VC10 showed as two distinct "blips" one just behind the first. No prizes!

[chevvron]

I do remember that on the acr430 (3cm) on an SRA a VC10 showed as two distinct "blips" one just behind the first. No prizes!

You had the gain control turned too high!