Specs on a big grey box

[KD7EDW]

I have been pouring through my  downloaded PDF scans of old Thordarson catalogs in vain, no luck. Anybody have secs on a big old gray box labeled with an aluminum tag  Thordarson Type T-49700 - Imprinted in Ink below that-  CTH-53461. I assume it is navy issue because it has the anchor symbol underneath. I assume it is also inductor of sorts (not a transformer)  because it has only two hermetic glass pin contacts.   

[KE6DF]

I believe the five digit Thordarson numbers were special OEM parts not likely to be found in a catalog.

[Todd, KA1KAQ]

There's a Thordarson catalog in the Technical Info section here (see left side menus) and Pat/KD5OEI who is a member has an excellent collection of info on his website:

http://www.bunkerofdoom.com/xfm/index.html

I've got several Thordarson guides, but no catalogs. They made great iron!

[K5UJ]

There's a Thordarson catalog in the Technical Info section here

Those are a bunch of single page jpg files.  I have a complete 1939 catalog as a single pdf:

http://amfone.net/Amforum/index.php?topic=20283.0

Rob

[KD7EDW]

Nice catalog scans -  but I have still not been able locate my specific item. I suspect that judging its appearance, it is post WWII  ,possibly later. If I cant find the specs, I guess I will have to build a Wheatstone bridge to measure it - my AADE Inductance meter wont read that far. How can one measure the current rating of an unknown inductor? I am hoping that I can utilize this in a   modified Heising modulator circuit.

[WA1GFZ]

an audio generator and series resistor into the choke will allow you to find the reactance.
Compare the AC voltage across the resistor and choke. Xl=2pi F L. Run the generator at 120Hz.
DC resistance will give you an idea of heat losses at operating current.
Measure the resistance of the choke. Then pump some DC current through it for a while so it warms up a bit. Measure the resistance again.
Smart guy Stu correct me here going from memory. Copper resistance goes up .4% per degree C. A mil grade choke don't run above 45 degree temperature rise. So don't run any current that increases the resistance more than 18%.
Or really go crazy and build a fixture to measure reactance with DC bias on the choke.

[KD7EDW]

Valuable technical info - thank you.
 

[k4kyv]

Good luck at finding info on old Thordarson transformers unless you have a complete file of their catalogues.  They seem to have arbitrarily changed model numbers every year or two, even for the same transformers.  I have had two transformers, for example plate transformers or audio drivers, that appeared identical in every respect, checked out electrically the same, and looked to be about the same vintage, but had completely different numbers stamped on the name plates. I have looked in vain through the catalogues in my collection, to find no model numbers that even resembled what was marked on the transformer in question.

[WB6NVH]

The majority of Thordarson transformers were made to customer specs and numbered with an in-house number only.  Thus the vexation happening these days when trying to figure out hamfest finds.  Maybe the company, which is still in business as Thordarson Magnetics, might be able to help.  They did once for me, about 20 years ago, no telling now.

CTH is a naval manufacturer code.  Can't recall what.  If it's something other than Thordarson, that might be of some clue as to where it was used.