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B is for - Feldfunksprecher b, b1, b2


Funksammler

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After the initial Blitzkrieg campaigns, the army decided it wanted a number of improvements made to its small portable radiotelephone (see Fuspr.a.1). Although the concept was proven the FuSp.a.1 had a number of weaknesses.  The switching between receive and transmit, the weak aluminium casing and the short battery life were addressed by a brand-new design using the new 2.4 Volt valves. Rather than an Anode battery, the new radio received a switched power supply (Wechselrichter) to supply the high voltage to the valves. The volume control and receiver fine tuning were fitted to a remote control unit that could be plugged onto the radio or worn on the belt. At the same time, the frequency range of the new models was slightly adjusted, the new "b" model  would operate from 90 to 110 MHz. Like before, the frequency dial was calibrated in channels, this time channels 211 to 240. The new radio was called the "Feldfunksprecher b" (Feldfu.b) and had a range of approximately 1.2 km. With that the channel distance about half that of the Fusp.a.1, two Feldfu.b's operating on different networks should be kept at least 20 meters apart and have at least 2 channels separation. To tell the Feldfu.b apart from other models, a red dot was painted on the rear lid and a red feeler shape added to the top of the casing. The antenna was also marked in red to avoid confusion.

The early Feldfu.b's had a 80 cm long two part sectioned antenna: a short antenna rod on the bottom and a longer "whip" section on the top. In 1943 the two part antenna was replaced with a 72.5 cm long foldable "Bandantenne". The bakelite casing of the Feldfu.b still proved too weak, the rim of the casing and the hinge of the rear lid would easily break so in early 1944 a sturdier casing was introduced and with it the Felfu.b1 model. In late 1944 a final modification was made, the electronic circuit was re-designed to contain one less valve, this simplified model was the Feldfu.b2. The Feldfu.b, b1 and b2 models remained fully compatible with each other. Below a comparison of the b, b1 and b2 models:

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From the front angle, the main identification is the the name of the Feldfunksprecher painted on the box. Likewise on the back of the box:

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Note the metal two part hinge for the back compartment door introduced with the Feldfu.b1. The b2 reverted back to the one part hinge. The early b-type box on the right shows its typical weakness: the rear lid has broken off at the hinge.

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From the top view, some changes to the shape of the bakelite box between the b and the b1/b2 models become apparent. Note the red feeler dots on top of the boxes.

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A comparison of the early b1 two-part antenna and the later foldable antenna.

The next two photographs aim to highlight the differences between the early b and late b1/b2 boxes:

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the early box on the right has a considerably thinner rim than the later box on the left. Also note that on the later models, rubber buffers were added to the box.

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Another view highlights the thin-rim early b model left and the thick-rim b1 model on the right.

The front panels show a slight evolution between the models:

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The only difference between the b and b1 models is the tag plate for the frequency calibration lock screw (top right of the panel). The B2 model is identical to the b1 apart from the colour change to grey. The back panels show a similar slight evolution (from the left: b2, b1, b)

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The early b lid on the right has a simple hinge. The inside of the lid has a plate describing how to fold the antenna and what accessories belong to the radio. The b1 model in the centre no longer has the data plate and a modified hinge design. On the b2 model the hinge design reverted back that of the earlier b, but a metal sliding guide was added to prevent the lid opening too far and breaking off. 

The inside of the detachable front lid contains a plate with the operating instructions for the radio:

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Although the operating instructions remained the same, different versions of the heading "Bedienungsanweisung für die Feldfunksprecher b, c, f und h" can be found. Early examples only mention the b and c, while later versions mention the b1 etc. This particular lid would be correct for a 1942/43 Feldfu b, c f or h.

Each Feldfunksprecher was supplied with a number of accessories:

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Here the accessories for the Feldfu.b1 are shown: 2,4NC28 battery (2,4 Volt, Nickel Cadmium, 28 Ah); a lumbar support, foldable antenna, Dfh.f headphones and Kmf.c throat microphone and remote control cable.

The battery was connect to the battery leads of the radio, these were shaped so that they could not be switched between + and -:

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Note how the shape of the positive contact prevents it to be connected to the minus side.

The battery slides into the battery compartment and is secured with a webbing strap:

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Note how on the b1 model, the double hinge allows the rear lid to be folded underneath the radio. Doing this with the the early b lid would cause it to break off.

The rest of the accessories tightly fit into the bottom compartment:

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To prepare the Feldfunksprecher for operation, the accessories are attached:

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Note how the cable from the headphones and microphone are held to the remote control cable with leather straps, this prevents the cables from snagging to other equipment worn by the infantryman. The Feldfunksprecher would be supported by the standard "Y-straps" of the infantryman with the lumber support held to the belt with leather loops. The infantryman's "A-frame" could be attached to the back of the Feldfunksprecher:

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A number of manuals and documents were supplied with the Feldfunkspecher:

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For those interested in the technology contained in the Feldfunksprecher, here is the circuit diagram:

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During reception, valve 1 serves as the HF amplifier stage, valve 2 as the oscillator/detector (superregenerative receiver) and valve 3 as audio ampllfier. During transmission, valve 3 serves a microphone amplifier with valve 2 as HF oscillator/power valve while valve 1 acts as a feedback amplifier. Also note that the receiver fine tuning uses an electromechanical drive to adjust a small capacitor. The supply voltage to this drive is controlled by a voltage regulator (EW = Eisen Wasserstoff Wiederstand = Iron hydrogen resistor) resembling a small lamp. If this resistor is missing or replaced with an ordinary lamp, the remote control drive will burn out. So never operate a Feldfunksprecher without first checking that the correct voltage regulator is in place!

In the later b2 model, the audio amplifier valve was omitted:

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Due to the omission of the low frequency amplifier stage, the Feldfu.b2 had a slightly reduced range from 1200 to 800 meters. The reduced range was however offset by a much longer battery life (roughly 50% longer) and a slight reduction in manufacturing cost and time.

Note: The development of the Feldfu.b2 demonstrates a key difference in the portable radio design philosophies between the German and particularly the US army. The Germans pushed their designs to achieve maximum battery life while the US pushed the levels of technical sophistication (using FM, AFC, squelch circuits etc.). This reflects the differences in the logistical situation faced by the German and US armies; the radio battery supply demands for a US unit were no doubt a multitude of those of a comparable German unit. 

The Feldfunksprechers were designed to be used by relatively untrained operators, they were typically carried by a runner staying in shouting distance to the unit commander. In some cases, unit commanders can be seen carrying the Feldfunksprecher themselves. Simple cartoon like instructions taught the operator the basic do's and don'ts:

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The final pictures give an impression of a "Sprechfunker" an infantryman carrying the Feldfunksprecher:

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He carries all the normal equipment of an infantryman. He has replaced his left hand ammunition pouch for a belt loop to make some space for the remote control of the radio. With the switchbox of the throat microphone he can switch between receive and transmit while the remote control allow him to adjust the volume and fine tune the receiver.

 

The Feldfunksprecher is attached to the belt and the Y-straps. All the normal infantry equipment can still be carried as normal. Normally the front lid would be fitted to the radio, the Sprechfunker is carrying the lid under his Y-strap until it can be refitted. Note how the remote control cable plugs into the radio.

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The A-frame is strapped to the back of the Feldfunksprecher.

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The infantryman has to be a bit careful shouldering his rifle but it just about fits next to the radio. The infantryman is now ready for his mission 

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The Feldfu. b is probably the most common of the Feldfunksprecher types found today. This is not surprising as every infantry company had four Feldfu.b's assigned to it. The Company commander could assign the Feldfunksprechers to his individual platoons as he saw fit. In defence the Feldfunksprechers were often use to back up important field telephone lines while during fast moving battles the Feldfunksprechers would become the main means of communication in the Company.

For security the operators would use code words for important commands, terrain features, commander names etc. These code words could be written with pencil on the white pad on the front lid. Some care had to be taken choosing words used, as with a throat microphone some letters like "s" and "f" can not be distinguished. To avoid confusion, a tag with the phonetic alphabet was also attached to the front lid. 

As with most radio equipment, finding the radio itself is only the start as the accessories are typically far more difficult to find. 

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Funksammler, you have an amazing collection as shown by your example photos. Thank you for taking the time and effort to explain the subtle differences between the different radio models. I am just getting started in the WW2 German Funk world and found your Post and photos very informative. As I accumulate Funk

information and reference materials I was wondering where I could get reproductions of the paper diagrams you posted as well as a copy of the small German Phonetic Alphabet piece displayed on the radio lid. I am also looking for any available information on the German Funk operational procedures that the soldiers used to actually transmit and receive voice messages.  I am very familiar with US Army procedures and assume the Germans used something similar, but would like to know exactly what they used. So, if you are aware of where I can find this information I would appreciate it. Danke sehr, Schorch.

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@Georg Neuner for the beginning look for a book "Panzer Tactics: German Small-unit Armor Tactics in World War II".

Germans coded their transmissions using "Sprechtafel", that book has some examples and is available online for reading.

Put into Google search "Sprechtafel" Panzer Tactics: German Small-unit Armor Tactics in World War II

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14 hours ago, Georg Neuner said:

Val, Thank you. I will. Danke sehr, Schorch.

Also look at this:

"Field codes used by the German army during the world war"

https://www.nsa.gov/news-features/declassified-documents/friedman-documents/assets/files/publications/FOLDER_437/41751269079046.pdf

But i think the radio communication procedures require the whole separate topic of it's own :)

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32 minutes ago, val said:

Also look at this:

"Field codes used by the German army during the world war"

https://www.nsa.gov/news-features/declassified-documents/friedman-documents/assets/files/publications/FOLDER_437/41751269079046.pdf

But i think the radio communication procedures require the whole separate topic of it's own :)

Although this is first world war it is an interesting read. During the second world war, different cyphers were used by the Germans at different levels. At the basic level of communication with the Feldfunksprechers, only a very basic Sprechtafel was used. Indeed better discussed as a separate topic.

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  • 2 weeks later...

In the past I have always been ademant that the Feldfunksprechers were only delivered in dark grey boxes, until I saw this: http://ww2germanoriginal.net/original-german-ww2-radio-feld-fu-b.htm

This is a very late war Feldfu.b2 box (with the wrong radio in it) finished in ordnance tan! I suspect this box originally held a 1945 dated Feldfu.b2.

So ordnance tan version of the Feldfunksprechers did exist after all, but probably only very few 1945 dated Feldfu.b2's and Feldfu.f1's...

 

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FS 

i was comparing psu of b ,b1 and the b2 , i have the same schematics 

like you , for the  b2 i guess C38 did’nt exist i don’t find it in b2 part list

it must be an schematic mistake , correct one will be C33.

 

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31 minutes ago, tornfuté said:

FS 

i was comparing psu of b ,b1 and the b2 , i have the same schematics 

like you , for the  b2 i guess C38 did’nt exist i don’t find it in b2 part list

it must be an schematic mistake , correct one will be C33.

 

Indeed some changes in the power supply as well, I guess they no longer needed the negative grid bias for the audio amplifier. The power supply filter also seems to have been redesigned so that he anode voltage could be upped during transmitting by shorting out W17.

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All the negative grid bias is omitted and the U3 transformer has also

        the winding 0 -45 omitted 

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  • 10 months later...

Hello guys. I'm new to this forum, and I have read some of these threads here with great interest. My name is Björn and I'm a Norwegian collector who mainly collects equipment related to the armed forces of the Wehrmacht Heer.
Some of you might know me from before - from the WAF, and from some debate groups on facebook. As I understand, quite a few of the members regarding communications equipment has migrated here from the WAF.
I was encouraged to join this forum by @Funksammler on one of the facebook groups.
Anyway, German ww2 communication eqipment, and especially the feldfunksprecher radios is of great interest to me. At the time being i have 4 such radios - 3 feldfu b's and one feldfu b1 (one of the feldfu b's is unfortinently missing the bakelite case) , I have one Handladesatz a, and one Frequenzprüfgerät f (unfortinently missing it's bakelite case) in my collection. I have succsessfully managed to bring all of them / keep all of them in working useable condition.

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Edited by Björn
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Anyway, while doing maintainance on the different radios, I started to notice some mechanical differences or evolutionary improvements that has been done.
I will try to post some pictures and explain what I have found.

 

First I have some pictures of a first spec. Feldfu. b.
This radio does not seem to have any evolutionary modifications done.

The first thing I noticed is that there is no stabilizing or reinforcement bracket on the R2 relay next to the RL2,4T1 tube. Marked with a red ring, where this bracket usually is mounted.
It does not look like that it has ever been mounted on this radio.

ba004a.jpg

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The other thing I noticed on this radio, was that it does not have reinforcement springs mounted around the antenna and ground-contacts on top of the radio unit.
Also note that the copper springs/contacts are riveted and not screwed to the chassi and to the porcelain antennabracket.

ba002.JPG

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This radio also came with a two-part Stabantenne 80 cm.
I had two antennas of this type, but only recently - a couple of days ago, I traded one of the two antennas away.

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Edited by Björn
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Thank you @val. Nice to see you again too 🙂
Absolutely - This forum platform has a lot more potential than the WAF. I am looking foreward to participate more here at MCN. The total forum layout is very good and easy to navigate in. And posting pictures is a dream. Not to mention the exellent layout of the threads - And I know for sure that we have the right crew as Moderators here too 😎

Anyway, back to the topic.
This antenna has the original leather strap to keep the two parts together. But the flexible whip has been repaired/replaced on it.

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Edited by Björn
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The next radio is a later Feldfu. b.
It's what I would call a hybrid between a Feldfu. b and a Feldfu. b1.
The antenna and ground contacts have received reinforcement springs to improve electrical connection.
The contacts are no longer riveted to the chassi and to the porecelain antenna bracket, but mounted with nuts and bolts instead.

bb002.JPG

Edited by Björn
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The Feldfu. b1 has got even more improvements.
The most importaint improvement is both a mechanical and electric improvement.
In all b models, there is a significant weakness in the grounding of the HF and transmission stage.
These two pictures are of a earlier b model.

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The module is secured with 4 screws. But only one (slightly larger) screw of the 4 is actually connected to the chassi and hence the only thing grounding the entire module to the chassi.
This screw is almost always a cause of problem or malfunctioning/reduced capacity of these radios. I have found on my own radios, that this screw was somewhat loose, and had a bad contact between the module and the chassi. I have taken these screws out, cleaned them and oiled them before putting them back in.
In one of my radios, I had a problem with Mithör from the throat microphone in RX position, and a poorly functioning R1 relay. It all came from this screw. (marked with a red arrow)
 b1015.thumb.JPG.f09a5d6d77c4ff4ad139bd85c2b05ba6.JPG

 

 

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And back to the b1 evolution of the feldfu radio.
The first thing i noticed, when cleaning the b1 frontplate, was a screw that I had not seen before on the other radios.

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b1010.JPG

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So I investigated a bit further, to see what this screw was connected to.
And look at this. The screw is connected to the HF module. It makes a very good grounding link between the HF module and the chassi. It is clearly a deliberate improvement of the weakness of the beforementioned single screw grounding of the HF module.b1011.thumb.JPG.f1d966ecc88b7ec0e57caf4332e675dc.JPGb1012.thumb.JPG.cd5b9a178a543248261960d5bd3766c5.JPG

 

The b1 model also of course has the support bracket for the R2 relay.

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It also has the reinforcement springs around the antenna and grounding contacts, (wich are secured with nuts and bolts, and not riveted together)
In addition the b1 model has also received a rubber buffer to the left of these contacts, to stabilize the top of the module and eliminate sideways movement against the chassi. (the module is still mounted on the pertinax plate in the bottom, and also this new grounding screw is located towards the bottom of the module) The rubber buffer secures it from sideways movement that in time might make the mounting and grounding screws come loose (the radio is made to be carried on the back in the field under combat situations.  It should withstand and work under lots of shaking and rough treatment).

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And the last difference or improvement that I have found on the b1 model, is the improved servicehatch for the RL2,4T1 tube.
This hatch now has a hole in it, and a small spring mounted, to ease the opening of the hatch and access to the radiotube.

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I hope these evolutionary differences that I have found, might be of interest to the community here.
After posting these differences that I have found on a facebook forum, @Funksammler confirmed after checking on his own radios,  that indeed after early 1944 the screw that connects  the HF module to the chassi is clearly a deliberate and systematic improvement of the weakness of the beforementioned single screw grounding of the HF module, And it is not only a special improvement on feldfu b1, but also found on 1944 models of feldfu f and also on feldfu b2

 

Best Regards
Bjørn

Edited by Björn
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Some "Feldfunksprecher in wartime use" pictures that I've picked up around the internet 🙂

 

 

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Edited by Björn
Wrong pictures were posted.
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