Today I took delivery of some military surplus radar kit. It is WR90 waveguide and reputedly it was a ground based radar in ~10 GHz and at one time in use with the Dutch army.

Given that it is of British origin, with mfg labels of Elliot, English Electric etc I hope someone on this list can tell me more about it?

it?



73 Wilko
PA1WBU

I'm guessing here but I think it could be the T/R section of a low powered radar set using a free running magnetron or similar as its Tx.

If so the componets are a free running LO (Gunn, Impatt or similar) - the grey rectangular block in the center of the U section. Then there are two single balanced mixers (top and bottom in the photos each with two screwed caps to retain the mixer diodes), a circulator (grey cube with one open port), a reflective self-ionising gas T/R cell (Black section above the circulator marked BS166).

The O/P of the transmitter would go into the open WG bend at the bottom of the photos to the circulator where it is rotated to exit to the antenna via the open port of the the circulator. A small sample of the Tx pulse is extracted on the semi-rigid in the bend section to feed the RF port of the lower of the two balanced mixers. Excess power from the transmitter which either leaks across the circulator or is reflected by the antenna ionises the gas in the T/R cell causing it to become reflective and so protect the top section from direct Tx power. The gas only remains ionised when the incident power is high and has a very short ionisation half life.

The recieved signal from the antenna exits the circulator upwards, through the T/R cell - which has negligible loss when not ionised - and goes the the RF port of the upper mixer. The LO O/P is split into two with one part feeding the upper receive mixer and the second feeding the lower Tx section mixer. The large silvered block at the top would be the first IF LNA.

The purpose of the Tx section mixer is to provide frequency feed back to the system (AFC) so that the IF remains centred in the IF passband on a pulse by pulse basis. My memory is not as good as it should be and I can't remember the correct acronym for this, but essentially the lower mixer gives an output frequency which is the difference of the free running LO and free running Tx (Ie the IF signal for that particular Tx pulse) and tunes the receiver to that frequency.

My neck is now well and truly on the block, enter a man with an axe stage right. :)

|Dave

PS if I'm correct the T/R cell will very likey have a mild radio-active isoptope either a s a solid or in gas form, this lowers the required incident power required to ionise the cell. It "should" be perfectly safe to remove the cell block from the assembly if undamaged but if there is a glass seal on both sides of the block when extracted I'd advise against opening it.

Dave

The grey oscillator is 99% likely to be a Gunn and not IMPATT - care and feeding of IMPATT would be too difficult. Besides, we at Plessey made most of the IMPATTs that others used, so I would have seen the body block of this somewhere along the line.

I CAN tell you that the oscillator is NOT Plessey and looks a little like it originates from Lincolnshire [MEDL].
The Vt terminal says to me that it's a varactor tuned Gunn, probably phase locked, but maybe just a tunable system. Had dealings with providing parts to Elliott, but not anything like this unit.
Anyone from Borehamwood around on here?
--
73, Paul Evans G4BKI [VP9KF]

On Wed, 15 Mar 2023 11:08:46 -0700
"Paul Evans EI6LC, G4BKI and VP9KF" <paul@...> wrote:

Anyone from Borehamwood around on here?

What sort of person are you looking for? I spent time there in 307
division in 1981-87 working in the microwave group but I doubt that
it's me you need.

--

Brian Morrison G8SEZ

I went to Elliott Borehamwood a couple of times on business. All a bit of a blur now. All I know is if I told you what it was about I'd be in trouble! No, I wondered if that ancient assembly marked with Elliott parts had come from their main site. Seems like it must've been from the late 70s or early 80s [I didn't look closely for any date codes]. Doesn't look anything like compact/light enough to be airbourne.

--
73, Paul Evans G4BKI [VP9KF]

On Mon, 20 Mar 2023 07:01:30 -0700
"Paul Evans EI6LC, G4BKI and VP9KF" <paul@...> wrote:

I went to Elliott Borehamwood a couple of times on business. All a
bit of a blur now. All I know is if I told you what it was about I'd
be in trouble! No, I wondered if that ancient assembly marked with
Elliott parts had come from their main site. Seems like it must've
been from the late 70s or early 80s [I didn't look closely for any
date codes].

If it says Elliott then it's probably a lot earlier than that as
Elliotts was absorbed into English Electric in 1967 and a combined
company with Marconi in 1968, even the Marconi-Elliott name had long
gone by the 80s, it became Marconi Avionics in 1978.

Just looked at the Google Maps satellite overlay of Elstree Way and
Warwick Road. It's totally changed since I last worked there 36 years
ago. I only recognise one building there and that's one that I think
was built in the 80s.

--

Brian Morrison G8SEZ

hi,

On Mon, 20 Mar 2023 22:41:51 +0100
"Wilko" <wkb@...> wrote:

For those who missed part of the replies flying around on this
subject: these are parts from a ZB298 Doppler radar set. Army stuff,
not air force.

See: https://www.cryptomuseum.com/radar/zb298/index.htm

Oh yes, my father-in-law worked on that in 305 division on Chester Road
through to the late 80s. He had some fingers in that particular pie.

--

Brian G8SEZ