Microwave Part - What does it do?

[jamesinnewcastl]

Hi All

The following may be out of scope for this forum so I'm happy for it to be removed but there may be people on here who could provide an answer or perhaps direct me to a more relavant forum?

I bought the attached item recently just out of interest. It has two waveguides each with a diode detector and a single Kystron. The diodes each have a connector as does the Klystron. The diode cavities each have a rectangular hole leading to under the Klystron. I've shone a light down each waveguide but the other guide doesn't show it, which suggests some tricky metalwork that I can't see under the Klystron.

One might assume that one waveguide transmits while the other receives but then would not one of the cavities just be a dead end?

Hopefully this is some standard configuration and purpose, any ideas?


Cheers
James

[lesmw0sec]

I was wondering if there could be some clever arrangement there for absorbing the transmitter pulse so as not to paralyse the receiver?

[M0FYA Andy]

Originally Posted by lesmw0sec

I was wondering if there could be some clever arrangement there for absorbing the transmitter pulse so as not to paralyse the receiver?

That would normally be done using a TR Cell, but I don't see one in the pictures.

Andy

[Jon_G4MDC]

Isn't it two local oscillators and two mixers? Duplicated receiver is my guess or otherwise could be dual doppler device for motion detection.

[ms660]

Is the klystron a CV1795 ?

Lawrence.

[jamesinnewcastl]

Hi

Thanks for the replies! Yes Lawrence it is a CV1795 also labelled Mullard KS9-20.

I've removed the Klystron but all that reveals is a hole where the tubes output wire goes so it isn't possible to look any further inside.

I've probed into the holes that lead to the centre of the device with a thin wire. There appear to be copper walls that route each 'hole' to the back and around to the middle of the device, beyond that I can't see or probe.

However by blowing into each cavity only one passes my puff to the Klystron output hole. That is the side with the 'tuning' screw. So it looks as if the other cavity hole is simply sealed off. That may also explain why there is no tuning screw on that side - I had thought that it was simply missing. However there is a soldered part on the tuning screw hole that couldn't just 'fall off' so quite what goes in the vacant hole is a mystery.

So now I am assuming that the Kystron emits only from one cavity and the device 'listens' from the other side. One diode to check on what is going out and allowing a tune, the other diode looking at the return wave.

I would still like to know more if anyone has any information. It is labelled 10D/18886 and is a R.F Unit Type 155 if that helps!


Cheers
James

[ms660]

Long shot but could it be part of this ?:

https://worldradiohistory.com/UK/Sho...ch=%22cv253%22

EDIT: Maybe not.

Lawrence.

[jamesinnewcastl]

Hi Lawrence

Max credit for even finding that ad! Looks like other people have also bought microwave stuff just out of interest!


Cheers
James

[M0FYA Andy]

OK James, telling us "it is labelled 10D/18886 and is a R.F Unit Type 155" most certainly does help!
It is part of TR3699 (10D/18625), the transmitter/receiver unit used in the ASV19A radar.
Picture attached.

Andy

[ms660]

Nice one Andy.

Lawrence.

[The Philpott]

ASV- Air to surface vessel?

[M0FYA Andy]

Originally Posted by The Philpott

ASV- Air to surface vessel?

Indeed!

Andy

[jamesinnewcastl]

Hi Andy

Excellent, you have come up with the goods once again! Now the next quest is to get a copy of the AP! After some digging I have found that any of the following might be useful:

AP 4400, AP4401, ARI 5834 (or 5301?) and ARI5838 (or 5301?). Kew have a copy but I'm not planning a trip yet.

Where did you get the picture? Hopefully one taken of your collection!

Sadly it looks like I will need a second tuning screw.


Cheers James

[M0FYA Andy]

James,
I have a PDF copy of AP4401, but it's not as useful as it might be insofar as there are no circuit diagrams or block diagrams of the units.
It covers the installation of ASV19B in the Fairey Gannet (I think the 'B' might be specific to the Gannet installation, but I need to dig further). There are however lots of pictures of the system in the aircraft and also pictures inside the equipment. It's a 30MB file, so I'll put it in Dropbox for you tomorrow.
I think the picture may well be of a TR3699 in my collection, but not taken by me, it may be from the seller when I bought it.

A copy of whichever AP includes circuit diagrams would be very interesting!

[M0FYA Andy]

James, I've sent you a PM.
Andy

[jamesinnewcastl]

Hi All

Andy's copy of AP4401 shows photos of the unit installed. From the annotation it seems that the Klystron mixes the reflected signal from the target with one diode while being protected from the transmit pulse by a T/R cell. The other diode just monitors the output for automatic frequency control. This diode being protected by a second T/R cell. This T/R cell has a spark gap that can be viewed through a window.

I am missing a tuning screw sadly. Interestingly the tuning arm of the klystron is attached to a screw mechanism allowing it to be adjusted from outside the unit.

The system uses 4 cylindrical enclosures for the electronics - was this to save metal and construction time I wonder ?

Cheers
James

[ms660]

For anyone that's interested, some sectional views of a 723A/B klystron which is similar to the CV1795:

http://www.microwave-museum.org/exhibits/mwm-001.htm

Lawrence.

[jamesinnewcastl]

Hi Lawrence

That is interesting, I always wondered how structures in the many diagrams of the Klystron could end up practically as just a plain cylinder. I also wondered about 'bending' the top of the jacket - seems very dodgy!

Cheers
James