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E is for - Feldfunksprecher Extra's

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Funksammler
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Since there is no "e" type of the Feldunksprechers, this is an opportune place to discuss some of the auxiliary equipment used with the Feldfunksprechers. The first is the "Frequenzprüfer f", a crystal calibrator used to calibrate the Feldfu.b and c models. The second is the "Handladesatz a", a manual generator used to recharge the 2.4 NC 28 batteries. The final is the Trb NC 28, a box designed to carry a spare 2,4 NC 28 battery.

The Frequenzprüfer f (Fprüf.f) came in the same bakelite box as the Feldfunksprechers so it could be carried to the frontline units if required.

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The top of the Fprüf.f was devoid of an antenna connection and had three round feeler shapes painted yellow. This allowed it to be distinguished in the dark from the Feldfu.b (one dot) and Feldfu.c (two dots)

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The yellow theme was carrying over to the rear lid, which had a yellow circle painted on it to provide easy visual recognition:

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The front panel held the frequency calibration unit at the top. There was no internal battery, so a battery cable allows the calibrator to be connected to a 2.4 NC 28 battery placed next to the unit. A calibration screwdriver on the bottom section completes the front panel:

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The Frequenzprüfer was a essentially a first line maintenance kit carrying spares and tools to test the Feldfunkprecher b and c models. Most of the space inside the box was reserved for spare valves and other bits of test equipment. The top compartment held a "Tasche (Fu) c" with spare valves, iron-hydrogen resistors, voltage indicator lamps, spare remote control units and test dummy load. The bottom compartment held a "Tasche (Fu) d" with spare vibrator units, Dfh.f, Kmf.c, test cable and microphone elements.

The two small bottom compartments were for two spare antennas (one Feldfu b and one Feldfu c) and two spare remote control cables.

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The inside of the rear lid contains a list of it's contents (not in such good condition in this example):

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The frequency tester itself contained a crystal oscillator that generates a very accurate frequency on 26 Mhz. It was to be placed one meter away from the Feldfunksprecher being tested and both units were switched on to warm up. The small amount of HF energy radiated by the battery cable would be enough to reach Feldfunksprecher:

DSC02677.thumb.JPG.1cc570cad49cd71736970e8242d0c27b.JPG

The Feldfunksprecher had to be tuned to the red channel (233 for the Feldfu.b and 203 for the Feldfu.c) with the receiver fine tuning set to the central position (so that the red dot is visible through the hole of the remote control unit). The Feldfu.b would pick up the fourth harmonic at 104 MHz while the Feldfu.c would use the sixth harmonic at 156 MHz.

DSC00548.thumb.JPG.d181f8a2045bc0a0a1eb74d60b244de0.JPG

After warming up for about ten minutes the static noise in the headphones of the Feldfunksprecher was checked. If a loud static could be heard, the tuning screwdriver was used to open the calibration opening (by turning the little screw on the top right of the Feldfunksprecher front panel) after which the trimmer behind the calibration opening could be reached with the screwdriver. The trimmer was now turned left and right until the static noise was at it's minimum. 

The Fprüf.f could only be used to calibrate the receiver of the Feldfunksprecher, to test the transmitter a second calibrated Feldfunksprecher would be required. Typically this would not be required as the transmitter largely uses the same oscillating circuit as the receiver. 

For transmitter testing, first the power output of the transmitter could be checked however using the "Senderprüfer a", a small dummyload fitted to the antenna socket of the Feldfunksprecher:

DSC02681.JPG

DSC02679.JPG

The "Senderprüfer a" should light up when the transmit button is pushed on the switchbox of the Kmf.c. Talking into the microphone should show a small variation in the strength of the light. 

Because the transmitter calibration could not be done with the Feldfunksprecher fitted in its case, a "Prüfkabel" was used so that the Feldfunksprecher could be operated outside it's box:

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With the "Prüfkabel" fitted, all the calibration controls inside the transceiver could be reached:

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Note that the antenna is no longer connected in this configuration but the short antenna contacts on the internal unit would radiate enough energy to be picked up by a second Feldfunksprecher placed some meters away. Both Feldfunksprechers would be adjusted to the red calibration channel with the receiver fine tuning set to the central position.

The transmitter switch on the Feldfunksprecher under test would be pressed and the signal would be checked on the second Feldfunksprecher. If the strongest signal should be achieved well within the range of the receiver fine tuning control. If this was not the case, the transmitter calibration trimmer (C9 in the schematic) had to be adjusted.

With these tests and calibrations done, the Feldfunksprecher would be once again ready for operation.

Similar frequency calibrators were developed for the Feldfu.f and Feldfu.h radios, these were the FPrüf.h and FPrüf.k respectively. In deviation from the calibration method described above, the FPrüf.h and k were used to calibrate the transmitter directly. For this reason they were provided with an additional headphone jack.

A second auxiliary unit required to keep the Feldfunksprechers operational would be the "Handlasesatz a" (HLS a), a hand operated battery charger. Again the bakelite housing of the Feldfunksprechers was used to house the charger so that it could easily to carried in the field to wherever the Feldfunksprechers were used:

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The bakelite housing the the HLS.a was left unpainted, strangely the inside of the housing did receive a coat of paint. The front panel contains the generator at the top and a battery tester plus connections at the bottom.

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The back of the HLS.a contains a storage space for up to two 2.4 NC 28 batteries, hand crank, loading cable, test cable and tree anchor:

DSC00539.JPG

The top of the box shows a small window under a cover. The HLS.a legend is painted in blue paint and a blue elongated feeler shape tells the HLS/a apart from all other versions:

DSC00535.JPG

The small window allows the speed indicator of the generator to be observed. A mirror inside the protective lid could be adjusted so that the indicator can be obverse while cranking the handle. This allows the user to keep the generator turning at the right speed for loading the batteries:

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the back of the panel shows a chained pin which can be secured in one of two holes. This allows either one or two 2.4 NC 28 batteries to be locked in place inside the box:

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The accessories and cables are shown separately, the strap of the tree anchor is missing here. The metal brackets could be screwed into a tree so that the HLS.a could be securely tied to the tree at a convenient height.

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The 2.4 NC 28 could be tested with the test cable and the battery tester: 

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If the battery required charging, it would be connected to the charging cable. If the battery was connected via the charging cable, it could also be tested by pushing the test button on the battery tester. With the crank handle fitted to the generator, the HLS.a is ready for charging:

DSC00542.JPG

Charging the battery with the HLS.a was a lengthy business. The HLS.a could supply a maximum loading current of 4 A, meaning that a full charge of a 2,4 NC 28 battery would take seven hours!

Normally, the battery under charge was placed inside the HLS.a, the charging cable was fed through a hole on the right bottom to the interior of the charger. The battery would be secured using the pin on the side:

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I can imagine that "charging duty" was not very popular with the soldiers. It is likely that turns were taken to operate the HLS.a. This also explains why the tree anchor was such an essential accessory, as he HLS.a had to be fixed in the most comfortable position for the lengthy charging process. It would probably have been a 24/7 job to keep a Company's four Feldfunksprechers up to charge....

Another late war accessory developed to extend the autonomy of the Feldfunksprechers was the Trb NC 28 (Trageblech NC 28) battery case for an extra 2.4 NC 28 battery. The 2,4 NC 28 battery fits snugly into the box:

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The Trb NC 28 was designed to fit against the back of the Feldfunksprecher; it was supposed to be connected by some leather straps and hooks to the D-rings of the Feldfunksprecher.

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However no Trb NC 28 has ever been found with the original straps attached, all boxes found today appear to be unfinished products recovered from factory stores (and judging from the writing on their lids, used postwar as storage containers for nuts and bolts etc.)

HLS.a can still be found regularly, most are in mint condition and 1943 and 44 dated. Since there is no mention of the HLS.a in earlier Feldfunksprecher manuals it is likely that it was only introduced late in the war. Most HLS.a's found today seem to have been unissued examples recovered from stores.

the Fprüf.f is a different story and is extremely rare. It is likely that a Division's Nachrichtenabteilung only had one or two Fprüf.f's to maintain the Division's stock of Feldfu.b's and c's. Given the high cost of Feldfunksprecher accessories today, it is going to be a challenge to restock a Fprüf.f with all its spares. Only one example of a fully complete Fprüf.f complete with the Taschen (Fu) c and d exists to my knowledge.

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tornfuté

Good job FS 

i will later post something about feldfu  test set , shall i post in E

or shall i open new post ? 

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Funksammler
Moderator
10 minutes ago, tornfuté said:

Good job FS 

i will later post something about feldfu  test set , shall i post in E

or shall i open new post ? 

Feel free to use the same threads, that way everything can easily be found together.

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tornfuté

Following werner thote , between 1941 and 1944 around 5.000 freq prufer f

 are made.

about Fu sp a 1 1937 -1938 1000 sets are produced

the total of all  the feldfu  produced  is 93.000 sets 

kifu d 25.000 sets 

 interesting  item , there was a rain cover  that plug in antenna base

when antenna is stowed inside the  box 

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val
Moderator
1 hour ago, tornfuté said:

Following werner thote , between 1941 and 1944 around 5.000 freq prufer f

 are made.

about Fu sp a 1 1937 -1938 1000 sets are produced

the total of all  the feldfu  produced  is 93.000 sets 

kifu d 25.000 sets 

 interesting  item , there was a rain cover  that plug in antenna base

when antenna is stowed inside the  box 

Do have any pictures of that rain cover?

Thank you for the numbers, @tornfuté

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tornfuté

Val first i have to find in which feldfu i have put it , it’s a replica made by Hutter

like the original one .

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val
Moderator
18 minutes ago, tornfuté said:

Val first i have to find in which feldfu i have put it , it’s a replica made by Hutter

like the original one .

No hurry, take your time :) thanks.

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val
Moderator
5 minutes ago, tornfuté said:

 Val i find it  🙂

 

Thanks @tornfuté

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val
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Björn

Very informative and useful thread. Thanks guys.
I do have a Frequenzprüfgerät f in my collection, but unfortinently without it's bakelite casing. However it is in working condition, and I have been using it to calibrate my radios.
It's a early apparatus, 1941 dated.

 

Frequenzprufgeratf074.thumb.jpg.3532b398a42d2ccfdf69e8a862230c72.jpgFrequenzprufgeratf012.thumb.jpg.4ce0e9ac793a1d386b4bdf569e5b69be.jpgFrequenzprufgeratf070.thumb.jpg.cfdbbfff572cac455d19a4351f961b55.jpgFrequenzprufgeratf006.thumb.jpg.9ecf1ffdf0ec8c442c23f29fa5ba65c1.jpg

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Björn

When the needle is within the green area, the frequensprüfgerät f is sending a signal that can be detected on the Feldfunksprecher radios. 
According to the users manual the Frequenzprüfer should be situated around one meter from the radio, when calibrating. But I've found that the Feldfunksprechers can recive the signal from 10 to 20 meters away without problem.

08.thumb.jpg.a6f47717feb0e539e93faa1a5229cfcd.jpg

Frequenzprufgeratf024.thumb.jpg.a8ac26cb05cd20f151fdca59a2e3f49c.jpg

 

Here are some pictures from the inside of the Frequenzprüfgerät f (undernieth the cover)

 

Frequenzprufgeratf077.thumb.jpg.2e9eaf3bf1597395dda0ae8236c53c14.jpgFrequenzprufgeratf107.thumb.jpg.69182a16464042388a1fa174bc98f359.jpgFrequenzprufgeratf121.thumb.jpg.972fb1ec42776ab83b640a2ca7ff4051.jpg

 

And some pictures with the RL2,4T1 tube, the 26MHz crystal and the Zerhackerpatrone removed.

 

Frequenzprufgeratf013.thumb.jpg.55d8ce803e98886d0d09fdfb484a1b40.jpgFrequenzprufgeratf016.thumb.jpg.f105b4e14e7247f6c97e76e3a7780a52.jpgFrequenzprufgeratf017.thumb.jpg.228399e70f3de9f1014dbc3b6ed34a14.jpgFrequenzprufgeratf030.thumb.jpg.3f9d1c3d132c7352189a5751e402a7f5.jpgFrequenzprufgeratf063.thumb.jpg.333315de911960a95f0c501169f4c4b0.jpgFrequenzprufgeratf050.thumb.jpg.8bd44b6a0405922bb2453c92bf038aae.jpg

 

A very interesting device, wich only needed a cleanup of the contacts inside the vibrator/Zerhackerpatrone to come back to life.

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Björn

But lets talk a little bit about the batteries for the Feldfunksprecher, the 2,4NC28.
The name 2,4NC28 stands for: 2,4 Volt - Nickel - 28 Ampere hours.

the NC abbreviation is often misunderstood today, and translated to Nickel Cadmium. This is wrong, as these batteries are Nickel Iron batteries.

[EDIT] : New undisputeable information presented to me proves me wrong in my last sentence here. These batteries are indeed Nickel Cadmium batteries!

I do not know how rare these original batteries are today, but I have found that they can be quite hard to find. And most of the batteries that surface today, are ground dug specimens from the battlefield in Russia.

However they do show up from time to time, but I would say that 99% of the good condition batteries that show up are either repainted, or missing their labels and original paint all together.
The main reason for this, is that spills of the elecrolyte inside these batteries, potassium hydroxide or Kaliumhydroxid - also known as Kalilauge has dissolved and ruined the original paint on these batteries.
The few pictures that i have found of 2,4NC28 batteries, that shows original paint points toward a light gray  color with a green horizontal stripe around the body of the battery.

 

 

5013335122_0.jpg

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images.jpg

post-56677-0-22171800-1481993704_thumb.jpg

web_bateri-001.jpg

Edited by Björn
Wrong information was unknowingly posted.

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Björn

About one year ago, I was very lucky to get hold of a original battery in very good condition, with original paint and label intact.

02.thumb.JPG.7e62978cf41d707978cc5afaa11b7007.JPG01.thumb.JPG.6967416cb26964d4dffa409654abb58a.JPG

 

And just a couple of weeks ago, I managed to trade for another 2,4NC28 battery from a collector-friend here in Norway. This battery was in quite good condition, but was repainted in a wrong color scheme. And It was missing it's original label as well.

 

03.jpg.393dee27e34cf09e1ba8a6a84e8b2909.jpg 04.jpg.042e66977451b4ace05f0a7d226c6a3a.jpg05.thumb.jpg.ef83d7b03a469f5f6967da06b40769ed.jpg06.jpg.f4d98fbdbadf8796314c5bb3531240dd.jpg

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Björn

About the label for the battery. I do have a loose original ground dug label wich I picked up on ebay a few years ago.

I took this label and scanned it in high resolution, and cleaned up the image on my computer.

 

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I then printed out a few copies in the exact same size as the original, on photo paper. I then laminated the labels to protect them from damage from elecrtolyte spills from the battery.

In the next picture, we see the original ground-dug label to the left, and the new, reproduced and laminated label to the right:

08.thumb.jpg.9f9dc1e7222637452cc91e68526c9f09.jpg 

 

 

 

 

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Björn

I then brought the battery that I have with the original color preserved, to a local paintshop in my town, where they have a scanner that can scan paint color and shade, and then mix an exact match. I got a small box of paint with the same color as the original battery, and cleaned and repainted the new battery that I got a few weeks ago.
I'm quite happy with the resault. I have not yet gotten around to get the 2,4NC28 lettering stencilled on the new battery yet, but with the new color and label it looks quite good, I think.

 

 

 

 

10.jpg

11.jpg

12.jpg

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Björn

But here's where it gets even more interesting. This type of batteries - originally a Thomas Edison Patent from 1901, are potentially still capable of being in working and serviceable condition.

I know, it sounds like a far reach, but Thomas Edison said in 1910, that his batteries would last for a 100 years..
Look at this article that I came across just recently:

 

https://newatlas.com/scientists-give-new-life-to-thomas-edisons-nickel-iron-battery/23102/?fbclid=IwAR2Y2riBBhgJbZ6bDjYIX0s16MotmuwnzEjk0HNo7XLMHq20_abBmzKHW90

 

They can possibly be revived and recharged and put into the Feldfunksprecher radios and used today - almost 80 years after they were made.
So I bought some pre-mixed Kaliumhydroxid from ebay, washed the batteries inside by filling a bit of Kaliumhydroxid in them, shaking them good and emptied them a few times, until what came out of them was clean kaliumhydroxid, void of any dirt and grime.

 

13.thumb.jpg.a9f9375c57d6d6cee31a98f9a609d2ae.jpg

 

Here's what I got out of one of the batteries, in my bathroom sink:

 

IMG_9805.thumb.JPG.3f5ec7096b295bde43aec932770aa6c5.JPG

 

And then I put the batteries on charge for around 10 hours each with 2 Volt and 3,5 Ampere.

 

14.thumb.jpg.2c9069a88ef19a7ba209835c13e54e36.jpg

 

And belive it or not, here's what I got today:

 

15.thumb.jpg.e625c61afcaea1e3833ced647f35d66c.jpg16.thumb.jpg.06db8e243737b5b20bd9fa0c5edb1f3f.jpg

 

 

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Desert Rat

Thanks for the images Bjorn, and the superb idea to rejuvenate batteries, I know that you can buy a special additive for example car batteries that gives them the longer life and it works very well, I have tried it on my van battery....very good!

Best to you...Desert Rat/ Ian

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val
Moderator
1 hour ago, Björn said:

the NC abbreviation is often misunderstood today, and translated to Nickel Cadmium. This is wrong, as these batteries are Nickel Iron batteries.

 

Sorry, you are mistaken here. NC batteries are Nickel-Kadmium. I suggest you to look at Die Sammler, page 58 and 59.

http://www.cdvandt.org/L-Dv-706-Die-Sammler.pdf

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Desert Rat

OK......Thanks to you, I will have look, as I thought it was the same chemicals used for any type of battery.....Now I know?

Best to you.....Ian

Edited by Desert Rat
correction to text

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Björn

Oh wow.
Thanks @val I learned something new just now. Indeed shown in the L.Dv.706 that you so kindly posted - Nickel-Cadmium it is. Definently!
I have edited in a correction of myself in the earlier post.
And thank you, @Desert Rat for your kind words 🙂

:smiley-face-soldier:

Edited by Björn
Edited out spelling errors.

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Funksammler
Moderator

The Germans did not really distinguish NiFe versus NiCad batteries, but generally NiFe were replaced with NICad equivalents as time went on. For example the pre-war NiFe "Edison Sammler" were later in the war manufactured as 12NC26. I do believe that by 1940, Cadmium mostly replaced iron in battery manufacture, so the 2.4NC28 is a true Nickel Cadmium battery. They are pretty robust, I have several originals still in use, but so do I have original 2B38's! The difference is that the 2B38's were dry-stored for 70 years, while the 2.4NC28's have held electrolyte for 75 years! I had an originally painted unfilled example, but the paint unfortunately did not last; similar to the Russian versions, they did not seem to have used an adhesive primer for the paint and it just falls off! 

regards,

Funksammler

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Desert Rat

Thanks Funks,Bjorn, Val

I am totally ignorant on these type of topics, but well appreciate your enlightenment to me. Reckon I must spend some time on these (to me) very difficult comms etc etc....But it's good to know that on MCN we have some very knowledgeable people.

Thanks to you all.

Best to you....Desert Rat

Edited by Desert Rat
correction to text

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