Fading wartime sounds

Page has been initiated on 26 March 2016

Current status: 5 April 2016

A

 

Last year Phil Judkins gave me a very rare present, consisting of a flat metal box with two special wartime recordings; containing curious signals once intercepted by a British Y-Service station at Southwold*

* It lays on the coast of Suffolk with now 1458 inhabitants. Please view for more on Southwold in Suffolk: https://nl.wikipedia.org/wiki/Southwold

Recordings made about mid 1943.

These gramophone disks are very curious. Consisting of a metal (iron) disk carrier deposited on one side with shellac. The metal carrier plate can just be noticed down the edge of the shellac layer; look for the typical metal-glow.

The disks are quite wobbling as you can notice on the two YouTube films.

The wobbling shellac layer might have been caused by the fact that shellac did not stick well onto the metal carrier. On the other hand, who once could have imagined that their recordings should once be reproduced, more than 73 years thereafter, on a world-wide-web; unimaginable in those bleak days.

 

Peter Boin was so kind to bring along a gramophone/amplifier fit for 78 rpm and dito pickup head for playing our two gramophone disks and making recordings

He created a CD quality format file, which cannot be listened on the web instantly. We therefore have to wait for a conversion into a MP3 format. For which I have to consult an expert, first.

His first attempt turned out being failure, because his mini-disk-recorder had lost, after some time, its data content.

For his second approach he brought along a classic Uher tape recorder, which worked ultimately well.

However, the major recording contents can be listen- and be viewed on the two YouTube links below.

 

YouTube films:-

Film 0220:    Peter Boin starts his recording. Content: German transmissions recorded about mid 1943 at the the Y-station Southwold. Recording disk consist of an iron ground-plate covered with a shellac layer; the disk is quite wobbling

Film 0221:*    The signal heard is probably a German radar signal. Please notice the very wobbling gramophone disk. Its basic carrier consists of an iron disk covered with a shellac layer.

* An error occurred, for what ever reason, apparently was left in my clipboard the first YouTube hyperlink address; so that both links pointed at the first film 0220. I cannot say why, but I was afterwards unable to get access to the 0221 (0225) video Stream data on YouTube. However, as previously referred onto - we had to make recordings twice, I have used now the according first video-film instead; you might notice the a bit different setting. Reason? Because YouTube refuses to upload the same film content twice. In Dutch language we say: geluk bij een ongeluk.

 

Maybe also of interest is another website providing German wartime signals recorded in Britain.         German Jamming Signals recorded by the BBC during

 

 

The next day, on 27 March, I received an e-mail reply from Peter Eijlander, who responded, very kindly, to an e-mail query on my behalf.

Quoting first from his genuine e-mail reply:

Interessant.

Ik heb je YT-filmpje bekeken en beluisterd.

Moeilijk te zeggen want het is een opname via een microfoon, het zou best nog eens rechtstreeks van het pick-upelement kunnen worden gesampled op een computer. Ik heb er nu een opname van gemaakt met Audacity en daarmee een paar plaatjes gemaakt.

Ik neem aan dat het toerental juist is?

De grootste amplitude (zie plaatjes) heeft een tijdsinterval van 0,005 seconden maar er zitten veel boventonen bij. De grootste amplitude bij een spectrumanalyse laat juist weer 430 Hz zien maar ook hier blijft het lastig. Er lijkt ook selectieve fading op te zitten, zo te horen.

Op welke frequentie werd dit uitgezonden? Wie pikte het waar op?

 

He did send me attached some screen shots made from analyses by means of his Audacity program.

 

 

A time spectrum plot, taken from the attached sound taken from the YouTube (video) film 0221

(Courtesy Peter Eijlander)

For those interested in a PDF version, please click at the above graph

Another option, copy this png picture and display (pasting) this directly at your computer screen

 

Viewing the timing scale more in detail

(Courtesy Peter Eijlander)

For those interested in a PDF version, please click at the above graph

Another option, copy this png picture and display (pasting) this directly at your computer screen

 

Analysing briefly the two foregoing signals, we might see a German radar signal.

But, the pulse-pause ratio is not like what radar signals should be about. Let us first notice what Peter has measured. He quotes 430 Hz PRF. Not yet 500 Hz what it once might have been constituted.

But, we must be aware of the various media (stadia) the original signal have been passed through before it did reach you and Peter's analysing program.

Second, the receiver type once used at Southwold. I know that the Allies favoured the National S27 type receiver.     My hypothesis: When you ever have worked with it and studied this set - you might have recognised that it was built within a metal housing. That is its only thorough means. However, its circuit concept was, frankly, rather basic; not very much more advanced than were broadcast receivers in those days. Its most favourable advantage, it covered frequency ranges not covered by (available) comparable receiver types.

Its bandwidth was designed for listening into communications, not being designed as to intercept quite wide spectrum signals.

But, the signal we are looking at does have only pulses of 430 Hz (500 Hz) PRF? Peter Eijlander used on 3rd April 2016 Peter Boin's (genuine) electrical recordings stored on a USB-stick and measured that the PRF was indeed 500 Hz. Please consider what this is about

 

Yes, but regular radar transmission pulses constituted of, say, 2 µs duration, the remaining time a radar system being switched-off in its listening for responses mode (call it echo mode). This implies, that we have to deal with a partial spectrum of, say, 100 - 500 kHz broad! Such bandwith the S27 type receiver certainly was not (well) fit for!

What I have neglected first, the bandwidth limitation of wartime 78 rpm recordings.

 

Maybe caused by the acoustic means of this YouTube recording. We may also noticing quite some rumble. Please look at  the very first photo on top of this webpage Now you may understand where some of the rumble originates from

(Courtesy Peter Eijlander)

For those interested in a PDF version, please click at the above graph

Another option, copy this png picture and display (pasting) this directly at your computer screen

 

The broad spectrum shown above, might have been caused by various means. Was it once in England recorded from a loudspeaker or electrically via a receiver output? Consider please also my forgoing considerations.

Second, what is audible on the YouTube films was done acoustically. Surely not the best means possible.

 

However,

Peter Eijlander kindly agreed to convert Peter Boin's .wav format files stored on an USB stick into a MP3 format file.

Herewith we will be able to provide it to you on this website. This will be a direct recording, not as is audible on the YouTube films. This way is also favourable for Peter Eijlander's audio analyses; at least the best way possible.

Please have yet some patience, because Peter should, Deo volente, get this USB-stick on 3rd April, and thereafter he needs some time to accomplish the job.  

 

(A)

On 5 April 2016

I was able to add MP3 files which Peter Eijlander kindly converted from Peter Boin's .wav audio files.

These are too large for application directly on the web, but MP3 must do.

 

   

Sound track 1 being made visible

 As to get a better reproduction please click at this graphic and open it in PDF format

An interesting finding: the recorded transmissions do have identifications given in Morse code. But were these of German origin or additional British markings? The solution is given within this recording, where near to the end the signal as well as the Morse recognition fades away (fading due to propagation)! Hence, the Morse signals were genuinely part of the (German) signal. When you listen carefully, you might even hear in the background an unclear voice lisping.

 

 

 

The tracks 1 - 4 are clearly pure jamming signals. Mostly operated when particular broadcast signals should be made unreadable to those these transmissions had been intended for.

An interesting aspect, once told by Hans Evers (PA 0 CX). He was a school boy in 1944 (HBS) and discovered on his clandestine radio receiver, that when the BBC started with their transmissions in Dutch language - the Germans instantly switched on their jammers. However, the BBC services did not transmit only Dutch language programs, but in sequences of, say, 15 minutes they switched over to, in his case, Czech language and the jammers in Holland have been switched off. But, it became now possible to listen quite comfortable to the Czech transmission, although, in the beginning he could not understand a single word. Though, after some time he became more acquainted to the Czech language and could at least grasp the main content of the BBC Czech language services.   

 

Because it concerns, according the below graph, a 500 Hz PRF, we may assume that it once originated from a: Mammut or Wassermann signal. Why? Because Southwold in Suffolk is situated > 100 km away from the European main-land. Freya or Seetakt had been systems operated quite near to the ground, hardly reaching hundreds of kilometres (line-of-sight limitation). But, Mammut, or even more likely the rather tall Wassermann (Allied code name Chimney), could reach 200 km up to 300 km. We may assume, in my perception, that the Wassermann signal may well have reached Southwold directly. Whether from the Dutch coast or Northern France or the Belgium coast stays open.

 

The signal of track 5 being displayed and measured graphically

As to get a better reproduction please click at this graphic and open it in PDF format

Please notice the pulse signal left of the left-hand side filter-edge. This might constitute a radar reflection, but how should we interpret it? We also hear some forms of signal fading; also known as QSB.

My hypothesis:

The likely target we are looking at is not necessarily in between Southwold and the origin of the radar signal source. I suppose it should lay somewhere on an virtual ellipsoid. Comparable to exploited in the Klein-Heidelberg system (bi-static radar). An ellipsoid has two focal nuclei, of which Southwold is one and the other one should be considered the location the radar (signal) source. For us today, it is impossible to determine where once the quite considerable reflected signal originated from. The range covered between the two filter edges is 600 km (λ of 500 Hz is 600 km). From the point of view from the radar station, with a PRF of 2 ms only half of the range can be exploited, thus 300 km (the signal has to travel from its origin to a target and its way back, providing a maximal range cover of 600 : 2 = 300 km). It is thus quite likely, that the German radar station might not have noticed this target signal at all. Or it had been displayed somewhere within his viewing range window covering 0 - 300 km. Nevertheless, it is quite unique that we can view a genuine still of a German 1943 radar signal.

 

Phil wrote me some days ago, that he has find an equal box containing another set of recordings; likely originating from the Southwold station too.

 

  To be continued in due course

 

By Arthur O. Bauer

 

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