Performance of radio sets

[trfh]

Folks,

great claims are made for German radio technology, not least by Arthur Bauer at http://www.cdvandt.org/ A nice summary is in Arthur's paper “The significance of German electronic engineering in the 1930s”, which is can be downloaded here.

What I am wondering is whether any work has been done on evaluating the performance of various sets using modern test gear? For instance, oscillator stability was supposed to be not far short of that obtained elsewhere with quartz stabilisation. So has anyone put these sets in an oven and checked it out? (And made the report public?)

The selectivity of the E-52 receiver is legendary, with its multiple tuned circuits in front of the mixer. But how about intermodulation - a parameter that you hardly hear mentioned as far back as WWII ( I have seen few figures for equivalent Allied equipment either)? We now know that intermod is a critical factor in receiver performance, particularly when you have several strong signals close in to your wanted signal. Anyone checked this out?

Some of the equipment is working at VHF. Anyone checked out noise figures of receivers, and compared them to those the Allies were achieving?


Richard

[Yuri D.]

Hello Richard,

Welcome to the forum!

You ask very interesting questions. I have a full RF testing lab where I can test for all of these parameters. Unfortunately I have been in school for the last 4 years and have not had the time to really play with my Wehrmacht sets. This will actually change this week, since my class load has decreased. I'll be glad to correspond with you and perform these tests, posting both the test methodology and test results to this forum.

Yuri

[trfh]

Tests on German radios - some background

Hello Richard,

Welcome to the forum!

You ask very interesting questions. I have a full RF testing lab where I can test for all of these parameters. Unfortunately I have been in school for the last 4 years and have not had the time to really play with my Wehrmacht sets. This will actually change this week, since my class load has decreased. I'll be glad to correspond with you and perform these tests, posting both the test methodology and test results to this forum.

Yuri

Yuri,

thank you for your welcome. I am very pleased to have found this forum - as a result of a google search, while researching German sets that operate above 50MHz. Your website has proved most helpful too.

Being new, I should really mention a bit about myself. I have some 25 years professional radio equipment and systems design behind me, after graduating from Cambridge in 1977. I started radio at the age of 12, messing about with junk sale radios in my bedroom. I moved on to operating British WWII era radios in the Army Cadet Force - that would have been 1971 - 74, when in my teens.

Starting in 1992, I developed an interest in radio history, particularly military communications kit. Naturally, being British, I started with the British kit I had used as a teenager. I have a reasonable collection of the British stuff, but for various personal reasons am only just getting a workshop back into full action, having had a "quiet period" for some years.

My own test gear varies from the expensive (e.g. HP8560E spectrum analyser) to the ancient (e.g. valve HT power supplies). Much of it is in need of restoration and calibration before it can be used in anger. I have, for instance, a complete HP8505A vector analyser system, but this needs attention......

My experience of German radio equipment is very limited (mainly because it is rare and expensive!). It amounts to no more than an attempted repair of an E-52a Koln receiver a few years back for a friend. When it arrived it was a severe shock to the system - since it took a while to work out what was a resistor, what was a capacitor, etc. The manuals were all in German (which I don't speak or read), and my workshop was in the throes of being moved and much of the gear was in storage......

To add to the difficulties, someone had been at this E-52, to the point where wrong components had been fitted, the dust cores had no threads and would move when they felt like it. To say the learning curve was severe hardly captures the challenge!

I didn't complete that E-52 repair, since the owner eventually wanted it back. I did manage to get quite a bit of it working, but the calibration of the front-end defeated me. I suspected that the optical dial was not the original one for this set.....

So, back to this thread.....I think that the Germans led the world in RF engineering during the period 1930 to 1942 (or thereabouts), but it would take this general statement further if some hard numbers could be gathered and published to prove this. I hope to be able to develop a full picture of German compared to UK and US engineering of this period.

I will be very interested to work with you, and anyone else on this forum who is suitably equipped, to establish test data on the various equipments.

In a few months, I should be receiving a Lorenz Lo40k39 transmitter for repair. While its in my workshop, I intend to run some of these tests, particularly stability with respect to supply voltage, and temperature. Harmonic output could also be checked, along with keying characteristics.


best wishes


Richard

[la5he@yahoo.no]

Perfrormance

As one who grew up using first German and later British/US surplus equipment
as a ham operator, there has never been any doubt that the German gear was superiour. Many years later, I became acquinted with Graham Winbolt in England . I recall seing in his collection some reports with assesments of the Nazi gear from a research establishment somewhere in the south. This goes back some 20 years so I dont remember more details.

The quality of the German equipment is of course why we all are facinated by it (and are prepared to pay for it !!!- )

The Lo40K is a work-horse. The stability is adequate on the lower frequencies, but using it on say 14 mHz, it has a chirpy tone. Key-clicks was also an issue.
I worked the Antartica with it on 7 mHz from a down-town Oslo location in the 1960s ! Using a Radione R2 for receiving.
Those were the days !!!

Ragnar

[trfh]

As one who grew up using first German and later British/US surplus equipment
as a ham operator, there has never been any doubt that the German gear was superiour. Many years later, I became acquinted with Graham Winbolt in England . I recall seing in his collection some reports with assesments of the Nazi gear from a research establishment somewhere in the south. This goes back some 20 years so I dont remember more details.

The quality of the German equipment is of course why we all are facinated by it (and are prepared to pay for it !!!- )

The Lo40K is a work-horse. The stability is adequate on the lower frequencies, but using it on say 14 mHz, it has a chirpy tone. Key-clicks was also an issue.
I worked the Antartica with it on 7 mHz from a down-town Oslo location in the 1960s ! Using a Radione R2 for receiving.
Those were the days !!!

Ragnar

Ragnar,

yes, I know Graham Winbolt slightly - he has disposed of all his collection now apparently. A small part of it has gone to the IWM at Duxford, UK.

I suspect there is more to collecting this German kit than just wanting good performance......after all, if that's all you want, then just buy modern Japanese kit, which having benefited from a few decades of development can perform better - or so I am led to believe! http://dev.wehrmacht-awards.com/foru...s/evilgrin.gif

The assessment you refer to is probably the one by Walter Farrar, who worked for SRDE during WWII. I met Walter about ten years ago, and he showed me the catalogue of German equipment he authored while at SRDE. He also wrote a well-known paper on German equipment, which can be downloaded from here.

I think Walter's closing comment in that paper betrays a certain bias (probably due to being on the winning side, he couldn't admit that the "enemy" actually did things better than the British did!), when he said:

"Electrically the equipment was good and efficient, but not modern when judged by wartime British standards, although it was in some cases quite ingenious".

I suspect Walter was plain wrong here - unless there is some aspect of British design I have yet to discover. Much of the British stuff dates back to the ideas of the 1930s, with very little innovation in evidence. Some items were obsolete before they left the factory - for instance the Wireless Set No.22.

One of the few truly innovative British sets was the WS No.42, but that was so late in arriving that the war in Europe was over by the time it became available - and nearly all of the 1,000 units made were shipped to the Far East, where they probably performed magnificently, but have otherwise been lost to history (though I have the only known set in the UK, courtesy of Graham Winbolt!).

The WS42 showed much of the same type of engineering as the German kit (maybe we learnt something after all!), and as it was designed at SRDE, where the German kit was also being evaluated, this cross-fertilisation of ideas is a distinct possibility. Unfortunately, all the SRDE wartime records are currently lost, so its difficult to prove this one way or the other.....

One obvious example of a good idea in the WS42 was the first use of the cast alloy case. The case was re-used in the R209 receiver, which many people on here will no doubt know well, but it started life with the WS42.


best wishes


Richard

[Yuri D.]

Hi Richard,

My experience starts and ends with restoring Wehrmacht radios. Although I've restored and calibrated several American tank FM sets (BC-528). My lab (shown on my site), is specifically equipped to restore WWII gear. I'm very much interested in RF engineering, and am learning that on my own.

My journey continues with this hobby, which will be life-long.

Yuri

[DrMemory1701]

Gentlemen,

Pardon the interruption, but after reading about your difficulties identifying
components in German Military radios and such hardware, I thought I might pass
this on to you.

It has Heer, LW, and KM parts identification as well as US and British designations.

http://cgi.ebay.com/Electronics-Geni...item4a96512391

The gentleman who sells this has offered it for some time.

[Val]

Folks,
What I am wondering is whether any work has been done on evaluating the performance of various sets using modern test gear? For instance, oscillator stability was supposed to be not far short of that obtained elsewhere with quartz stabilisation. So has anyone put these sets in an oven and checked it out? (And made the report public?)

Here's link to two material, where russians measured performance of two german radio - FuHEu and T9K39.

http://www.rkk-museum.ru/documents/a...es/2-46-01.pdf
http://www.rkk-museum.ru/documents/a...es/2-46-02.pdf

Clearly here is not used any modern test gear but neverertheless they are interesting documents. Alas - they are in russian, but a believe it's natural language for Yuri? Maybe he finds little time to write here up little summary for all?

[Yuri D.]

Ill give it a shot. Thank you for the post

[Yuri D.]

Here is the translation of the CONCLUSIONS section of the T9K39 document:



Conclusions

The design of the T-9K-39 required high selectivity, frequency stability and the implementation of a new tuning scale system which has high accuracy of gradations and accurate representation of the tuned frequency. The unification of these factors almost automatically resolves this problem.
The analysis of documents from tests carried out in the laboratory of the 6th department of the Scientific Research Institute of the Red Army, and documents of German tests carried out in the laboratories of the firm “Telefunken”, showed that the receiver T-9K-39 conforms to the submitted requirements.
The application of a powerful preselector, and two quartz crystal filters in the intermediate frequency stages, satisfied the first requirement of high selectivity. High quality of variable capacitors, low trans-conductance, and compensation for frequency drift due to self-resonance by trimmers, provided high frequency stability of the receiver.
Stretching of the frequency scale using an optical system to a length of 2 meters provides accuracy in reproducing the tuned frequency, with a maximum deviation of 300 Hz at 8 MHz and 500 Hz at 10 MHz.
The high accuracy of the scale’s gradation is accomplished with high quality of engineering and precise execution of the optical scale’s mechanism and system.
A relatively low sensitivity, especially in telephony mode, is characteristic of German receivers of most recent manufacture, since for audio reception with high selectivity, the necessary voltages are 100 to 200 times lower than those determined for normal sensitivity, but the noise level is also dramatically reduced. In the T-9K-39 receiver, this requirement is satisfied.
The combination of the above-mentioned qualities with the given constraints of the receiver has made the construction very complex in general, and especially in specific areas, namely the frequency range switch and the optical scale mechanism.
Despite the complexity of the schematic and especially the construction, the receiver has a number of qualities, both electrical and constructional, which deserve deeper analysis and understanding with the goal of utilizing them in a receiver of 1st class.
Electrical qualities to be studied:
1. Schematic of the pre-selector and high-frequency resonant circuits in the 1st and 2nd blocks.
2. The choice of magnitude and method of correction of the amplitude of the 1st heterodyne on the control grid of the mixer across the frequency ranges.
3. The implementation of the two quartz-filters in the intermediate frequency stages with bandwidth control that allows the bandwidth to vary from 120 Hz to 8.5 KHz.
4. The utilization of a negative reverse feedback in the low-frequency stage.

Construction / mechanical qualities to be studied:
1. System of the stretched optical vernier-scale mechanism.
2. Construction of the frequency range selector switch.
3. Construction of the bulkhead of the variable capacitor.
4. Modular construction of the entire receiver.

[la5he@yahoo.no]

[QUOTE=Yuri Desyatnik;4775096]Here is the translation of the CONCLUSIONS section of the T9K39 document:


Anybody needing an original manual ?