USN TDY jammer assembly types

[Ian Roberts]

Hi all -

I'm not sure if this is the right sub-forum for posting this query but please feel free to let me know and/or move the thread!

I have recently taken up 3D model making using Blender and I am working on creating a model of the TDY jammer assembly as seen aboard ALASKA (CB-1) in 1945. I've noticed during my research that there are multiple external forms this jammer assembly could take depending (I assume) on date of install and where it was installed, etc.

Later installations seem to universally make use of the 10AFJ antenna pedestal, equipped with the various types of reflectors available (10AKL, 10AKJ, 10AKM, 10AJY) which covered different frequency bands. Friedman's Naval Radar mentions that these reflectors could be swapped around by the ship's company "in about an hour" if required. Here is the later installation with 10AFJ pedestal and AKL/AKJ antennas installed back to back (I understand that the 10AFJ pedestal could rotate to bring the proper antenna to bear):



This excellent photo of WASHINGTON (BB-56) in late 1945 shows the later type installation on the small platform below the air defense level: http://navsource.org/archives/01/056/015645r.jpg

Also visible here is another TDY on the after side of the fire control tower about one deck level down, facing starboard and aft -- I assume this is a fixed installation designed to cover the obvious blind spot from the TDY on the front of the fire control tower. This 12 July 1945 photo of INDIANAPOLIS (CA-35) also shows the later TDY jammer at the foretop: http://www.navsource.org/archives/04/035/0403541.jpg

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The later installation is very well documented and finding plans of it is straightforward -- what interests me for this project is what I think must be some sort of "early" or "interim" rotating antenna pedestal for the TDY seen on ships in late 1944. I have been able to identify a similar installation aboard ALASKA (CB-1), INDIANAPOLIS (CA-35) in early 1945, NORTH CAROLINA (BB-55) in 1945, and aboard MISSOURI (BB-63) during the surrender.

This photo of ALASKA in 1945 shows the TDY very clearly at the air defense level -- most artists have shown this as the later type installation: http://www.navsource.org/archives/04/1201/04020130a.jpg

This photo of INDIANAPOLIS (19-N-76909) during the December 1944 yard period at Mare Island shows the early TDY at the foretop (it was later replaced with the 10AFJ pedestal and two reflectors): http://www.navsource.org/archives/04/035/0403521.jpg

This photo of MISSOURI at sea (80-G-376365) on 20 July 1945 while refueling shows the early type TDY bracketed below the air defense level forward: https://www.navsource.org/archives/01/016341c.jpg

Unfortunately there is no higher res version of 80-G-376365 I have been able to locate.

This photo of NORTH CAROLINA in July 1945 (80-G-469988) shows the same installation roughly even with the air defense level on a small bracket forward: http://navsource.org/archives/01/055/015545o.jpg It seems the pedestal base and the bracket are still present on the museum ship, with even the cabling for the unit running aft under the air defense level: https://i.redd.it/oue8ai86rqq31.jpg

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Some key observations on the "early" type antenna pedestal are that the supporting stanchion for the antenna reflector is vertical without any tilt associated (like 10AFJ), and that only one reflector seems to be fitted. The pedestal does seem to rotate to "aim" the antenna down a specific bearing much like the 10AFJ pedestal later on (as evidenced by the photo of NORTH CAROLINA - 80-G-469908 where the antenna is slewed to port). The reflector on all of these early installations seems to be the larger corner reflector of the 10AKL antenna.

I believe the model of TDY fitted to ALASKA is the earlier type -- specifically because the reflector support appears as a square shape behind the reflector, instead of the circular support of the 10AFJ pedestal (in front elevation view, with the reflector facing the viewer bow-on).

Does anyone here have any information on this early type of TDY installation beyond what I've deduced above? I'm sure the unit was fitted to other ships (I just don't know which ones and discovering the above has been by happy circumstance). Any help is appreciated!

Also, a very good document describing operation of the TDY is available here: https://www.ibiblio.org/hyperwar/USN/re ... index.html

Cheers
Ian

[BB62vet]

Ian,

I've looked over all my .pdf's on naval equipment (elec/RADAR), Fieldman's Naval RADAR's, and P.E. Law's Shipboard Antennas and haven't found anything in the way of details regarding the size, etc. or dimensions/drawings of the TDY antennas. I saw on Hyper-War where your illustrations came from but other than that, I'm drawing a blank.

I have a copy of the 1960 USN shipboard antennas catalog and only found this -

66AKJ TTY Illustration:

66AJX TTY.JPG

Don't know if it's any help or not.

I'm also into the 3D design/printing end of ship modeling and am working on several display models of Fire Control Directors/RADAR in 1/96 or 1/100 scale and may go up to 1/48 scale just to see how they look.

Good luck with your project!

[Ian Roberts]

Much appreciated!

I had found that same illustration too but it shows the later 10AFJ pedestal and not the early type. I was able to piece together a very basic 3D model in Blender based on photos (and known dimensions of the reflector), but have to caution that this is very much a "guesstimate" based on blurry/low res photos, usually taken from an extreme distance.

Here are some views of the component I created:

[BB62vet]

Ian,

Glad to have helped you out - I just today found this illustration from the TFD MISSOURI Plan Book - a variation of the earlier picture but with more dimensioning, in case you want to revise, etc. -

TDY-1 From Plan Book.jpeg

I was actually looking for other equipment details and saw this picture which may/may not be helpful.

Hank