Racal Clansman TUAAM military antenna tuner unit teardown

[MrSlack]

This is a Racal TUAAM automatic antenna tuning unit or ATU. Nice bit of kit but basically the function is to automatically match an antenna to the radio set and feed without any technical knowledge. This was usually bolted to the front of a Land Rover in a box and deployed as part of the Clansman radio system. It covers HF bands only from what I can find out about it. On a quick observation, so don't quote me on this, it does it's thing through RF sampling and a fully analogue control loop that controls the variable capacitors driven via motors. I suspect this uses a crude servo system looking at the system layout. There is no microprocessor or intelligence in this at all, it's all electromechanical and analogue glory! Examining everything, the last date code is 1991 so not that old either.

Bought this to nick the air variable capacitors from. Turns out to be a goldmine of nice parts. Total cost £16.50.

Comes in a large sealed milspec aluminium case as expected. This is promised to the wife as a plant pot. The outside is boring so I've omitted it.

Inside views:









And the boards...





There are three motor driver boards. On the basis that there are 4x BFY52s, they look like H-bridge configuration with a canned 741 op amp. There are two misc control boards, one containing a dual opamp, a single opamp and a ton of diodes and I assume this is the brains of the device. There is a tiny switch mode identified by a big transistor, a canned 723 regulator, power transistor which is pretty cool as it's powered via a 12v source and based on the symmetry of the board it looks like it generates two voltage rails for the opamps. The side of the unit has the RF section which I haven't dismantled yet. Maybe tonight but I've got to get the kids from school now...

[RobertoLG]

cool!!! thanks for sharing 

[MrSlack]

Correction: VHF band. 24v operation.

[Richard Head]

I bet you feel guilty dismantling that work of art! You could put it in a glass case in your entrance hall!
It looks like a Pi network with the motors adjusting the caps. I've seen similar designs used on armoured vehicles to match the vertical whip (very low z) to the 50R radio. Some even have a dual directional coupler to dump the reflected power at very high SWRs. Unfortunately the variable caps are not very high voltage judging by their size.

[MrSlack]

Slightly but I'm going to be honest but the outside of the unit was knackered. I was expecting it to be in slightly better condition. The power feed and the BNC were bent and broken so this one is a bit past display. The wife is getting a plant pot out of the casing so she's happy. It has even been suggested that I get a couple more to make a display 

I think you are right about the Pi network. There are two appropriately sized air core inductors hanging off the back of it and a signal relay as well. Appears to be wired to switch the inductors inline as well. Correct with the whip; this is usually connected to a whip on the front of a land rover as follows. The unit actually fits inside the box:



I don't think there's a high RF voltage here at all. That's fine for me as I'm running 12v

[xygor]

What is that air filter looking thing?  Is that a breather port?

[MrSlack]

I think it has a dessicant in it. It's not connected to the outside at all. I've wrapped it in tape in case it has anything nasty in it.

[Richard Head]

There's normally a little glass window on the front panel that changes colour when the humidity increases above a certain limit. Some manpack radios also have the little clear window and are are filled with dry nitrogen and sealed. 

[CJay]

Beautifully made piece of kit, I bought one last year just to see what was inside it and do a tear down but fell foul of respect for the quality of it.

Now it's sat, forgotten until I saw this post, in a corner of my shed.

I might buy another to tear down, might even have a go at getting it to work on 6M...

[chris_leyson]

Nice teardown and a nice piece of kit, thanks. For a while I worked at RACAL BCC in Wembly tuning up a later model ATU. Can't remember the model number but it used two banks of glass capacitors switched by vacuum relays and a bank of six inductors, again switched by vacuum relays. The whole thing was driven by an RCA 1802 (COSMAC).

[MrSlack]

Sounds a bit meatier than this thing! 1802 was a popular CPU for milspec stuff. I've not managed to get my hands on one yet.

Slightly less enamored with the construction after spending an hour extracting the caps this afternoon as it was rather difficult as i can't extract the entire inner frame. Two of the caps don't have end stops on them. They do have universal joints which is pretty neat for something literally static at both ends. Motors and gearboxes are very nice.

Going to reverse engineer and bring up the power supply later as it's a rather neat little unit and it seems a shame to chuck it.

[Gyro]

I think it has a dessicant in it. It's not connected to the outside at all. I've wrapped it in tape in case it has anything nasty in it.

Yes, a standard desiccator and humidity indicator as used in all Racal military kit. It's non-hazardous.

Edit: If the window is/was still white then you can be pretty sure it hadn't been opened.