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PostPosted: Sat Jun 09, 2018 1:11 am 
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Location: Corvallis, Oregon, USA
Michael,

The SPS-30 transmitters were in the superstructure below the radar tower where the antenna was mounted. See this link for images of the after superstructure and radar tower:

https://www.okieboat.com/CAD%20superstructure.html

Attachment:
SPS-30 RF path.jpg
SPS-30 RF path.jpg [ 138.69 KiB | Viewed 254 times ]


The S band waveguide came out of the top of the superstructure and up to below the tower deck. Then it passed through the deck just in front of the antenna base. You can see it in the attached image (red line), where it comes up, curves and enters the base just below the foot ring.

From there it rose up the vertical center axis of the base to a rotating waveguide coupling at the very top of the drive platform - the rectangular box contained the slip rings for electrical signals and power and the waveguide coupling. The elevation platform, dish reflector, support arm and scanning head rotated around the vertical axis.

The microwave signals passed through the rotating waveguide coupling and followed a waveguide to the left (looking toward the scanner head) side of the elevation platform where the waveguide curved downward to another rotating waveguide coupling on the horizontal axis of rotation for the elevation platform.

The signals passed through this rotating coupling and into a waveguide inside the support arm leading to the rotating waveguide switch in the scanner head. I have shown the path into the top of the 20 parallel waveguides coming from the rotating switch in the scanner head.

All of this waveguide plumbing was pressurized with dry nitrogen. The SPG-49 tracking radars were also pressurized (I am not sure about the SPS-10 and SPS-43 radars) so you have to figure there were leaks. If you look at my CAD model you will see a lot of green nitrogen gas bottles attached to the superstructure (there were even more in internal compartments).

Phil

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PostPosted: Sat Jun 09, 2018 1:31 am 
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Jodie,

We had a tracking console in Weapons Control where we could control the SPS-30. It had a small joystick that we could use to set the bearing and elevation for the antenna. Just move it a little bit and tons of antenna would jerk around at the top of the tower. I don't recall for certain, but I'm sure the tracking system was programmed to oscillate the antenna back and forth while doing the vertical scanning to get an accurate height reading for the target.

In heavy seas the ship rolled +/- 30 degrees and pitched +/- 5 degrees, and the radar antennas were at the top of tall towers where they gyrated wildly in 100+ knot winds, rain, hail, snow, ice and salt spray.

When operating the SPS-30 and SPS-43 radars with their huge antennas it was always in the back of my mind what enormous stresses were being forced upon the structures when you changed rotation speeds or just gave that joystick a little twitch.

Phil

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PostPosted: Mon Jun 11, 2018 6:14 pm 
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Thank you, Phil, the illustration makes it very clear. It is remarkable how many turns the wave must negotiate before it finally hits the parabolic reflector.

Jodie, if you have a link to that video I would love to see it.

Michael


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PostPosted: Mon Jun 11, 2018 6:52 pm 
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Here are some images of the elevation drive mechanism. All of the pitch, yaw and elevation mechanisms are very similar - five drive systems in all.

The electric motor drives a screw thread gear that moves a threaded shaft. The darker gray vertical shaft is actually threaded, but I am cutting corners on this one. Screw threads bloat the file size tremendously, and the overall ship is already approaching a gigabyte. So use your imagination.

The lower bearing blocks are attached to the elevation platform. The upper bearing blocks that support the drive mechanism are mounted on the drive platform that rotates around the vertical axis.

The elevation motor moves the threaded rod up and down and this tilts the elevation platform up and down. The tall tube on the top of the assembly is a housing to protect the screw threads on the rod. Originally the lower part of the threaded rod had a rubber cover that protected it from the elements. It would stretch longer or shorter as the antenna was elevated or depressed. But the rubber cover was exposed to sunlight, salt spray and very high winds and that meant a fairly short lifetime.

The last picture shows the drive mechanism installed near the back of the antenna assembly.

Phil


Attachments:
SPS_30 elevation drive small 1.jpg
SPS_30 elevation drive small 1.jpg [ 36.86 KiB | Viewed 212 times ]
SPS_30 elevation drive 2 small.jpg
SPS_30 elevation drive 2 small.jpg [ 39.58 KiB | Viewed 212 times ]
SPS_30 elevation drive 3 small.jpg
SPS_30 elevation drive 3 small.jpg [ 76.94 KiB | Viewed 212 times ]
SPS_30 elevation drive 4 small.jpg
SPS_30 elevation drive 4 small.jpg [ 55.63 KiB | Viewed 212 times ]

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PostPosted: Tue Jun 12, 2018 7:36 pm 
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mcg wrote:
Jodie, if you have a link to that video I would love to see it.


This link from the CBS News coverage of the Gemini 9A recovery in 1966 should start at about the right moment to see it:

https://youtu.be/ge5jhyk16Zs?t=9m8s

Look closely and you can see the SPS-30 start to slowly sweep back just before the cutaway. They cut back to the same angle about 30 seconds later and you can see it again.

(Use this link with caution - this live coverage from back in the day is addictive.)

Jodie Peeler


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PostPosted: Sat Jun 16, 2018 8:11 am 
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Thank you! A real time trip...


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PostPosted: Wed Jun 20, 2018 10:08 pm 
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Michael,

In my description of the waveguides in the SPS-30 antenna I left out an important detail. Between the base and the first rotating wave guide coupling on the drive platform the waveguide passes through the pitch and roll stages. These are driven to keep the drive platform level as the ship pitches and rolls. The waveguide must pass through two more rotating couplings in these stages.

From the antenna's viewpoint the base (with ship attached) can rotate about the vertical axis to sweep out a conical area, pivoting around the port/starboard axis (the pitch platform) and the fore aft axis (the roll platform).

Right now I don't know exactly how this worked - I am working on it.

Phil

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PostPosted: Thu Jun 21, 2018 6:17 pm 
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Tough to visualize. From the image of a cone, I am kind of wanting to imagine a gimbal or a ball-and-socket. But it appears a waveguide can only rotate around one axis. Is there a vertical displacement between the two (i.e. pitch and roll) rotors?

Incidentally, it is CAD at its best, your re-creation of this beautiful machine. An amazing challenge. Michael


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PostPosted: Sat Jun 23, 2018 1:02 am 
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Michael,

I have a few close-up high resolution photos of the base, roll, pitch and drive stages, and it does appear that the waveguides do have vertical displacements for the roll and pitch joints. I haven't determined the dimensions yet - too many other things interfering with the CAD modeling.

It should be fairly simple because every turn, bend and joint in a waveguide attenuates the signal a bit.

Phil

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