Teardown: Siemens Hilfssender (auxiliary transmitter), microwave tube based - Page 1
Forum section: electronics / rf-microwave

author: wkb
author_rank: Super Contributor
timestamp: March 20, 2016, 06:18:43 pm
content: On yesterday's hamfest over in Rosmalen (NL) I obtained a rather interesting piece of kit. It calls itself Siemens Hilfssender. Or: auxiliary transmitter, built by Siemens of Germany.It has a microwave tube, an adjustable cavity (from what I now know), it is built from silver plated brass, it weighs a ton and is testament to the proverbial Deutsche Grundlichkeit. I think it is for use around 2.4GHz (assuming I interpret the readout correctly that corresponds to thetuning of the cavity).I am really curious if one of the EEVbloggers has any clue what this puppy belongs to? I also wonder about it having only one RF connection? Oscillator? I cannot find a partnumber on the tube unfortunately.

author: wkb
author_rank: Super Contributor
timestamp: March 20, 2016, 06:20:42 pm
content: Partnumber badgeOn the bottom the adjustmet axle, with the frequency readout scale

author: wkb
author_rank: Super Contributor
timestamp: March 20, 2016, 06:23:30 pm
content: on the side is a pickup for the RF sticking in the cavity (detailed picture follows)The axle at the bottom allows adjustment of the cavity

author: wkb
author_rank: Super Contributor
timestamp: March 20, 2016, 06:28:03 pm
content: Screw-on cap for access to the tubeAnd the cap itself, with strong spring

author: wkb
author_rank: Super Contributor
timestamp: March 20, 2016, 06:31:22 pm
content: Once the cap is removed the tube socket becomes visible.With the side cap on the cavity removed

author: wkb
author_rank: Super Contributor
timestamp: March 20, 2016, 06:36:22 pm
content: The retainer ring held in place with two screws is removed, tube-socket assembly pulled from the cavity assy.Connections between the tube and the 'outside world' are provided via silver plated slide contacts

author: wkb
author_rank: Super Contributor
timestamp: March 20, 2016, 06:37:35 pm
content: Deeper inside lies a coaxial socket for the RF side of the tube.

author: wkb
author_rank: Super Contributor
timestamp: March 20, 2016, 06:39:09 pm
content: Tube is fixed within its socket with yet another retainer ring.Detail of the socket.

author: wkb
author_rank: Super Contributor
timestamp: March 20, 2016, 06:40:47 pm
content: More detail on the tube socket.Towards the other end of the cavity, the adjustment mechanics

author: wkb
author_rank: Super Contributor
timestamp: March 20, 2016, 06:45:04 pm
content: Multiple gears are in place for mechanical adjustment of the cavity. The main axle adjusts 'something' in the cavity, but there is another adjustment possible using a screwdriver which controls another gear which in turn appears to move a metal tube in/out the cavity.Other pictures will detail that.

author: wkb
author_rank: Super Contributor
timestamp: March 20, 2016, 06:47:01 pm
content: Mysterious cable connection.And more gears

author: wkb
author_rank: Super Contributor
timestamp: March 20, 2016, 06:48:42 pm
content: That cable againNote the position of the readout versus the position of the metal tube shown in the other picture

author: wkb
author_rank: Super Contributor
timestamp: March 20, 2016, 06:51:46 pm
content: Note the position of the readout versus the position of the metal tube in other picture. Frequency /cavity has been adjusted

author: SeanB
author_rank: Super Contributor
timestamp: March 20, 2016, 06:53:56 pm
content: That is very interesting there, a tunable oscillator in the ISM band. I would guess it was for either RF heating of small samples or ionising gas samples in a gas chromatograph.

author: wkb
author_rank: Super Contributor
timestamp: March 20, 2016, 06:56:44 pm
content: RF pickup unscrewed from the cavity

author: wkb
author_rank: Super Contributor
timestamp: March 20, 2016, 06:58:58 pm
content: Detail of the extended tube

author: wkb
author_rank: Super Contributor
timestamp: March 20, 2016, 07:03:00 pm
content: Right.. these are all the pictures I have sofar. Wondering if I want to take the cavity assembly apart or not. Chances are I will not be able to reassemble it

author: TimFox
author_rank: Super Contributor
timestamp: March 20, 2016, 08:16:00 pm
content: The actual tube (valve) in your picture is a "lighthouse" disc-seal triode. The American tubes with that construction and octal base include the 2C40. Seehttp://www.radiomuseum.org/tubes/tube_2c40.htmlTo operate at high frequencies, the cathode (through a capacitor) and grid connections are concentric discs to minimize parasitic inductance. The heater connections and multiple cathode connections are to the octal base.

author: wkb
author_rank: Super Contributor
timestamp: March 20, 2016, 08:31:07 pm
content: Quote from: TimFox on March 20, 2016, 08:16:00 pmThank you! Looks like the specs are like:https://www.sokoll-technologies.de/Museum/Auto/Dokumente/Datenblatt_2C40A_General_Electric.pdf. Telefunken, a leading German firm also produced them, so it can very well be a TFK tube in this Siemens design.I'll pull it apart again to see if I can find a partnr hidden somewhere. Other than powering it up and creating the mother of all WiFi jammers I do not see much use for it myself.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: March 21, 2016, 07:24:26 am
content: Should be bias pins (heater, cathode/grid, plate) somewhere; simply apply the respective voltages and you get RF. Wouldn't think it would be enough for plasma -- just a few watts -- but might serve as any number of things: reference or VFO for a power amp (doing such things perhaps), or LO for a mixer in a radio set, or..?!Tim

author: Nuno_pt
author_rank: Frequent Contributor
timestamp: March 21, 2016, 09:17:07 am
content: At first glance that seems to me like one TWT amplifier for Microwave, the tube is similar of the 2C39.

author: wkb
author_rank: Super Contributor
timestamp: March 21, 2016, 09:46:09 pm
content: I decided to take the cavity further apart. The tube/valve had no visible partnumber.Split in two halves.A look into the silvered cavity tube, down into the finger-stock connectors that connect to the triode

author: wkb
author_rank: Super Contributor
timestamp: March 21, 2016, 09:48:31 pm
content: More close up look into the cavity.The center connector that connects to the top of the light house triode valve.All is beautifully machined silvered brass. Gorgeous..

author: wkb
author_rank: Super Contributor
timestamp: March 21, 2016, 09:52:32 pm
content: The cavity adjustment 'piston' set for different frequencies.

author: wkb
author_rank: Super Contributor
timestamp: March 21, 2016, 10:05:57 pm
content: The central connector to the triode can move in and out of a silvered tube. This is adjusted using the slotted screw I mentioned in one of the earliest posts. Not sure what it is used for. The main axle moves the 'piston' in/out the cavity, the slotted screw independently moves the tube in/out.Clues as welcome

author: wkb
author_rank: Super Contributor
timestamp: March 21, 2016, 10:09:17 pm
content: Close up of the top connector connecting to the top connection of the lighthouse valve.2nd picture shows the valve mounted into the top connector.

author: wkb
author_rank: Super Contributor
timestamp: March 21, 2016, 10:13:21 pm
content: In case someone has a use for it or just wants to own this beautiful piece of German engineering please get in touch via PM.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: March 21, 2016, 10:37:05 pm
content: Interesting, I wonder why it's stepped -- filtering harmonics, perhaps?So it has two adjustable cavity lengths / loading tweaks? Probably something like, tuned plate / tuned grid oscillator.Tim

author: Alex Eisenhut
author_rank: Super Contributor
timestamp: March 23, 2016, 02:08:06 am
content: Here is the LO from a 1L30 spectrum analyzer. It is tuned by turning the knob on top that lowers and raises two coaxial plungers inside the cylinder. I think this tunes two cavities that act as LC circuits on the cathode and plate of the tube inside. The grid is grounded, and two wire loops that pass through the triode's grid flange couple the two sections.http://www.r-type.org/exhib/aaa1026.htmSo on the oscillator you have two wires for the filament, one connection for the B+, two coax outputs; one goes to the input mixer, one goes to a PLL, and a connection to a varactor that's somehow stuck inside a cavity with a wire loop to fine tune the oscillator. In the analyzer it is locked against a 1MHz crystal.It's a mess to take apart, and the tube is machined to fit in there, you need the special modified Tektronix tube, a normal one won't fit and you need the holes for the loops.

author: wkb
author_rank: Super Contributor
timestamp: March 23, 2016, 09:23:55 am
content: Interesting! Given the ident plate on my unit I do not think it originates from a measurement instrument but the pictures look sort of similar.

author: wkb
author_rank: Super Contributor
timestamp: April 04, 2016, 06:10:49 pm
content: In case someone wants it, I have put it on a Dutch classified ads list for €10. More than happy to trade for something useful too.

author: cj
author_rank: Contributor
timestamp: May 24, 2016, 07:08:51 am
content: What you have here is an auxiliary radar transmitter. It uses the 2C43 tube and can generate 1us pulses at 1000 pulses per second and produce up to 1.7kW.If you google ‘pulse communication on 2300mc’ you’ll find a pdf document describing a pulse communication system using this type of oscillator.CJ

author: wkb
author_rank: Super Contributor
timestamp: May 25, 2016, 07:49:12 pm
content: Quote from: cj on May 24, 2016, 07:08:51 amFascinating, thank you for the information!