E 102a

The coarse altitude radar/receiver-display module



Status: 21 November 2016




During the course of this brief survey on the recently acquired E 102a receiver-display module, it was found that some components were missing from the CRT-deflection section; which is attached onto the E 102a receiver section.


Last Saturday, looking at a corner-shelf in our main exhibition space, my attention was incidentally drawn:


What did I see?

A second AT 102 A defection module, without CR tube!




let us first dealing with our recently obtained E102a module.



Ln 29451

Werknummer 951083


Huth-Apparatefabrik Hannorver G.M.B.H

Viewing the components, it must have had quite strong links with Dutch Philips (Philips Berlin was only a sales office). On the other hand, there are strong signs that Dutch Philips once might have been the main contractor, and due to the circumstances of War - Huth-Apparate took over the job completing the contract ultimately.

However, most of the components are typical Philips style.

But, Philips certainly was not the genuine designer of this set; this once was F.F.O.


Before going into details, I first would like to give some technical specs of this coarse altitude meter.

The transmitter frequency was about 182 MHz

Measuring range was between 200 m up to 12,000 metres, I suppose that this limit was more due to practical reason, as the returning signal strength versus receiver sensitivity including noise floor might not have allowed for weaker signals.

Although, the time base frequency was 29.5 kHz

peak-power at the antenna 80 W

Transmitter pulse-width 0.3 s

The scale range being calibrated between 0 to 5 km

When levels above 5 km had to be dealt with, one should also consider the regular barometric altitude meter. An 7 km altitude was read off at 2 km (5 + 2 = 7).

But there hardly can be a mistake of 5 km altitude level.

Hence, 10,000 m was read off at 0 km (2 x 5 km)

For those interested in the technical details, please consider the FuG 102 A manual-link down this page.


Let us continue with this report:


Viewing E 102a from a bit different perspective. Please notice the tube which has been pulled out. Such provision is meant for as to prevent for hampering stray-light



About 1974, I visited Horst Beck for the first time. During this occasion he proudly showed me this module; particularly impressing me for what was inside

Since I have looked for it, but up to recently it didn't work.

Maybe this module originates from a bit later wartime production, where metal-protection wasn't commenced as was done in the earlier stages of war. Or, simply time have passed since more than 42 years; more than 71 years have since the end of WW II.

Have you ever seen a wiring like this?

The wires are not of the regular type, but was likely from Philips origin. I know that these were heat resisting and some linen have been used for it as well; I suppose that some glass like insulator was incorporated in it as well.


The interconnecting wiring of the upper receiver-deflection module is entirely running on the outside of this module; on VHF constituting an effective capacitance against ground.

Not yet noticeable: not all valves are visible, because on the inner-side of the upper module is also a circuit layer including valves!




This photo shows the rear side of the E 102a module

Please notice what I a few lines up already mentioned, that the lower side of the upper module is having its own circuits including the according valves.



Before detaching the upper the upper module from the AT 102A section, we take a look at the right-hand side of the module



Module ET 102a

Sachnummer 124-150.02A  also known as Zeichnungnummer, which actually pointed at the according design-drawing

Anforderz. Ln 29462 constituting GAF stock number

Werknummer 338852 is the coded production number. For example serial number:- 852 or 388 or whatever key they once might have used

hdb   = Huthapparatefabrik



Viewing at the receiver circuit

Please notice the two valves up on the right-hand side, where apparently two valve anodes and screen grids being wired as a triode.



The valves R 10 and R 11 constitute the video output stage

Viewing carefully the circuit wiring, it becomes clear that not a single circuit was maintained on one side of the module, but that it goes from the output of a valve to the grid of the next valve which is on the opposite side of the module (meandering).



The receiver/deflection module has been detached from one another

The two contact pins belong to the antenna-signal input; the upper pin is connect onto the core of the coaxial cable.



Looking now at the opposite side of the module

During earlier days in the war, they might have used a protecting paint as to avoid oxidation of the Mg die-casting.



The module being turned a bit



Looking at the upper side of the AT 102A frame section

The trimmers down on the right-hand side are meant for aligning the pained circle on the rang-screen appropriately. 



Apparently, the previous owner was also faced with lacking of some essential components

Sad, but we have to live with it. 



Lacking the according components with their according labelling, I would like to get proper photos of this section, so that we know where to search for



One aspect is clear, essential components, like potentiometers and resistors; likely also the Sikotrop like Philips imitations are doubtless originating from pure Philips production

In my early days I vividly remember the catastrophic quality of the Philips potentiometers. One was always the case, noisy potentiometer contacts. Real horrors!



The shaft up left proves that the previous owner tried to made the best out of his display



Does a bell ring next?


The left-hand module we know, but the right-hand one?

There hardly can be a doubt that both chassis must have had something in common.

But why?

Apparently, in the early days just after Germany's collapse in May 1945, there existed a sever shortage on everything.

There must have been a bunch of E 102a frames (chassis) around. Whether these were empty or already in a stage of completeness, I cannot answer.

Telefunken converted these frames and made out of it a most simple oscilloscope. Without any sort of amplification provision, than the sensitivity of the LB 1 CR tube involved. The LB 1 might have been available, because these had been manufactured in quite huge numbers.

For example, its sensitivity is: 5 V/mm!

This figure equals the sensitivity given at the specs of the LB 1 CRT. 



On 21 November 2016




Last year in France, I obtained, among other bits and pieces, a part of a module. I acquired it because I was so desperately looking for a genuine E 102a receiver unit; time and again it proved to be impossible for us to lay our hands on it!



Clear is: that what is lacking in the foregoing photos is implemented here entirely

By the way - both modules have once been manufactured- or had been delivered by 'hdb', which once stood for:  Huthapparatefabrik Hannover.


What an amazing finding!


It is becoming evident, that there weren't lacking a few components, but quite many!



Apparently, the one we bought at an auction in Munich recently, wasn't really 'untouched'

However, it proves that what is missing on the newly discovered module can easily be taken from the one obtained from the recent auction.



A minor problem constitutes the lacking connectors which should interconnect this AT 102A module with the one we bought on the recent auction

Please compare this photo with the next one.



Looking at a photo from the foregoing series.  It is evident that what is missing on the previous photo is available here, and what lacks previously is here present


Among this second AT 102A module, I found at the same shelf a cover belonging to a S 102A transmitter.     Now we are also looking for a S 102 A Sender module! Also because we  possess already for quite a long time the rotary power supply type U 102 A.


For those interested in the integral FuG 102A manual


Fug 102 A Elektrischer Grobhoehenmesser Geraete-Handbuch


The electric schematic in A5 size



By Arthur O. Bauer