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Plessey Watchman primary radar

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Plessey Watchman primary radar

Old 28th Nov 2018, 02:38
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Originally Posted by P160 View Post
The Heathrow 23cm radar was mounted on a concrete tower adjacent to Terminal 1 car park in the central landside area by the exit/entrance to the tunnel giving access to the terminals from the A4 and M4 spur. It was known as the "Car Park" radar and was removed from service and its replacement operates from Bovingdon, near Hemel Hempstead. To give better low level coverage in the absence of the 23cm radar another Raytheon ASR10 was installed southside near to T4, this supplemented the Raytheon ASR10 east of what was T2, The Queens Building and T1, these both replaced the Watchman which was sited where T5 is now. For interest the Watchman replaced the Plessey AR1 sited just north of T3 and the Cossor ACR6 which was sited south of T3 where AOSU is or was in 2010 when I retired. The building of T5 also nessesited the resiting of the DF and the Rx site.
Apologies; I remember the Perry Oaks Watchman now. Vague recollection that a Heathrow controller told me they didn't use it much as its site meant it had poor low cover, plus it was in the way of T5 development.
When Farnborough opened LARS East, the T2 10cm was piped in but we preferred to use the Pease 23cm or the Car Park 23cm until one day a NATS engineer came down, fiddled with one of our displays, then got up and left after announcing we now had the T4 10cm instead of the T2 one. Course we couldn't use it straight away as he didn't leave us any paperwork but next day I was on LARS East and had it selected when a helicopter called me between Herne Bay and Reculver at 800ft and to my amazement I could identify it! I found the low cover from this radar was superior to the Car Park 23 cm so from then on, used it in preference.
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Old 28th Nov 2018, 02:47
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Originally Posted by Mooncrest View Post
What becomes of the obsolete radar heads and towers ? NATS had plenty of Watchmans (if that's the right plural) which have all but completely disappeared. Sold on or end up in a scrap yard ?
The Farnborough Watchman was owned by MOD so they took that back and installed it elsewhere (mid 2003), but they didn't want the consoles as these were being replaced by raster scan displays so they were left in situ when the old tower was demolished in 2003. We did have a 6th console in the final few months of the old tower and this was a raster scan one so we all assumed this is what we would get in the new tower but we got TFT displays instead although the CAA were reluctant to approve them until very close to 'O' date (22 Nov 2002); can't remember what happened to that console or whether it was owned by NATS or MOD.
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Old 28th Nov 2018, 12:06
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Nice to see there is life in the old systems after their heyday, as it were. Otherwise, there is a lot of scrap metal in the gantries, towers and aerials (assuming they're not made of fibreglass).
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Old 28th Nov 2018, 18:18
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Originally Posted by Mooncrest View Post
Nice to see there is life in the old systems after their heyday, as it were. Otherwise, there is a lot of scrap metal in the gantries, towers and aerials (assuming they're not made of fibreglass).
Now you come to mention it, I think the Watchman reflector was fibreglass.
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Old 28th Nov 2018, 18:41
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You are correct Chevron, it was a composite sandwich. Outside layers of glass cloth and epoxy resin with an inner metal sheet layer of aluminium, after all, glass cloth and resin are transparent to radio waves.
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Old 28th Nov 2018, 18:44
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Thanks for the info P160 - didn't realise there were so many heads around Heathrow.
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Old 28th Nov 2018, 19:40
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Just for interest, when I first started at LHR in 1978 there were four Marconi 264H radars, one Cossor ACR6, one Plessey AR1 and one Decca ASMI surface movement radat. When I left in 2010 there were two Raytheon ASR10's and four Terma SMR's plus two Qinetic FOD radars, and they all worked magnificiently despite my efforts and harsh language.
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Old 28th Nov 2018, 21:26
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I suppose you can never have too many radar heads, provided they compliment, rather than cause grief with, each other. Glasgow once had a pair of Marconi 264s and Leeds Bradford kept the ACR430 going for several years after the Watchman was commissioned. It will be interesting to see if LBA plumps for its own SSR aerial when the Watchman is replaced, which can't be too long away.

A thought has just occurred to me. Are radar towers meant to be frangible or not ? It might depend on proximity to runways, protected bits and so on.
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Old 29th Nov 2018, 08:07
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Radar towers to the best of my knowledge have never been constructed with mechanical fuse pins to make them frangible due to the tremendous side loads imposed on the structure during high winds and also because they are usually well offset from the direction of travel so to speak. The only frangible airfield installation I came across was the STAN 37 Localiser which had aluminium fuse pins between the ground mounting bolts and the lattice uprights.
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Old 29th Nov 2018, 11:27
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Thankyou P160. I never considered those points, plus the weight of the aerial would call for a robust structure. Glidepath aerials, on the other hand, are definitely designed to give. I've seen the sorry remains of one at LBA.
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Old 29th Nov 2018, 11:59
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This is a picture I found via Google Images, taken by George Woods, and shows the Marconi 264 that was mounted on the Maintenance Area MSCP.. I believe it was sited to give LATCC improved low-level coverage, possibly before the EGCC HSA 23cm tower was built?

Rumour has it it's short lifespan was due to it's effect on TV/radio reception close to the site? I know the EGCC 264H had the same feature, a short 'buzz' each time the aerial rotated. It even affected the cassette-recorder I had as part of our 'directed studies package', provided by John Dougan

The Sub-Centre ops room was screened with mesh and industrial-grade tin foil, as the beam's passage also affected the Mediator System Displays.

Last edited by ZOOKER; 29th Nov 2018 at 15:03.
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Old 29th Nov 2018, 12:36
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Fascinating picture ZOOKER. I hate to be contrary but is this definitely EGCC - Manchester ? I remember the 264 but it was mounted at ground level near the RW24 threshold, as I recall. Also, I don't remember a spiral ramp at the multi storey car park. Nice Egyptair 707 as well.
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Old 29th Nov 2018, 14:06
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That image is the LHR Marconi 264 atop of the BA staff car park in the BA maintenance area east of the terminals and yes, that with the other three 264's did cause TV interferance which is why we no longer use the 50cm band. The body responsible for frequency allocation, the ICU decreed in the mid 70's, the closure of the 50cm to civil radars. The TV band overlapped the 50cm band hence the interferance so all users of this band were made to discontinue usage, the 23cm and 10cm are the lowest bands available for civil radar. This happened in the late 70's into the 80's to allow withdrawal and installations of radars, the LHR 23cm became operational about 1984/85. The BA car park radar was replaced by the EN4000, a hybrid of AR1 Tx/Rx, Marconi 7113 processor and a Cossor ACR6 aerial.
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Old 29th Nov 2018, 14:46
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Thankyou P160. I didn't think I was looking at Manchester but I couldn't have been certain it was Heathrow either.
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Old 29th Nov 2018, 15:05
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The best radar we had at Heathrow was the ACRVI, especially when one of the Tels chap ("Tiny") got his trimming tool in it and tweaked it up!
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Old 29th Nov 2018, 15:15
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Mooncrest, yes apologies it is a slightly ambiguous post. The picture is, as P160 says, the BA base on the east side of EGLL. The 'CC 264 was originally sited NW of the R/W 20 threshold, about where the cargo sheds are now. By 1979, it had moved to where you say, roughly where the MCT DVOR is sited today. There was a rumour that the EGLL 264 aerial from the BA car-park was used to replace the one at Manch', but I don't know whether that is true.
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Old 29th Nov 2018, 15:25
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I thought the short lived radar on the BA car park was a 23cm Marconi 654, replaced by the 23cm HSA radar on T1a car park.
We had a 50cm Marconi 232 at Farnborugh until the Watchman was installed, 1991 I think and it too made a 'beep' on the RTF every time it rotated.
I believe there was a 10 cm Plessey AR15 at Luton which wouldn't interface with other LATCC radars so it was just switched off and left there.
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Old 29th Nov 2018, 16:10
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This radar business is clearly far from simple. Different towers and plinths for mounting, numerous possible sites, different manufacturers, assorted wavelengths, displays and individual nuances. An interesting subject.

I wonder if Talkdownman at Lasham would like a Watchman or S511 when the 424 eventually pegs it ?
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Old 29th Nov 2018, 17:12
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Chevton, the BA car park was a 264H 50cm, put up there to increase low level coverage but was not succesful due to the fact that the anntenna design required a ground plane 5o form the beam pattern, hence all 232's and 264's were mounted at ground level. Up on top of a car park was a big mistake as the formed beam was a crock so it was short lived, it was a "told you so" moment in the engineering department.
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Old 29th Nov 2018, 19:09
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Originally Posted by Mooncrest View Post
This radar business is clearly far from simple. Different towers and plinths for mounting, numerous possible sites, different manufacturers, assorted wavelengths, displays and individual nuances. An interesting subject.

I wonder if Talkdownman at Lasham would like a Watchman or S511 when the 424 eventually pegs it ?
I'm sure they'd love it at Lasham; problem is they can't upgrade their equipment too much as they'd lose 'grandfather rights' status (operating APS with A/G and without ADV/ADI).
Maybe TDM will read this and elucidate.
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