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About RF Cafe

Kirt Blattenberger - RF Cafe Webmaster

Copyright: 1996 - 2024

Webmaster:

    Kirt Blattenberger,

    BSEE - KB3UON

RF Cafe began life in 1996 as "RF Tools" in an AOL screen name web space totaling 2 MB. Its primary purpose was to provide me with ready access to commonly needed formulas and reference material while performing my work as an RF system and circuit design engineer. The World Wide Web (Internet) was largely an unknown entity at the time and bandwidth was a scarce commodity. Dial-up modems blazed along at 14.4 kbps while typing up your telephone line, and a nice lady's voice announced "You've Got Mail" when a new message arrived...

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Nazi Morale Radio
October 1945 Radio-Craft Article

October 1945 Radio-Craft

October 1945 Radio Craft Cover - RF Cafe[Table of Contents]

Wax nostalgic about and learn from the history of early electronics. See articles from Radio-Craft, published 1929 - 1953. All copyrights are hereby acknowledged.

National Military Markings Flying Aces November 1934 - RF Cafe"Morale Radio" sets were manufactured by many companies and provided to service men for entertainment and hearing news from back home and around the world. Unsubstantiated sources claim American companies were paid cost + 15% for each set. Other countries made similar "Morale Radios" for their troops, or procured sets from elsewhere and made necessary modifications to suit their format. Not a whole lot of information can be found about them on the WWW, and finding a photo of one of the German Wehrmacht radios with the Swastika and eagle on it is darned near impossible, other than the one shown in this 1945 Radio-Craft magazine article. Part of the reason for the scarcity is the German people's desire to destroy as much of the Nazi (National Socialist German Workers' Party) history as possible both to put the horrible era behind them and to help reduce the potential for war crimes to be traced back to them. The Swastika is a particularly despised symbol of the regime and is now outlawed in Germany (other than in museum-like settings).

Interestingly the Germans were not the only country that used a Swastika for military markings (click thumbnail above). I was surprised to find in a 1930s Flying Aces model airplane magazine that the European countries of Finland and Latvia used Swastika insignia.

Nazi Morale Radio - Presents Interesting Contrasts to U. S. Sets

By Alan Jay

Rear view of the Wehrmacht "Morale Radio - RF Cafe

A rear view of the Wehrmacht radio showing components.

Front view of the Wehrmacht "Morale Radio - RF Cafe

The front view of the Wehrmacht radio.

The Nazi Air Force, in a last minute effort to boost the morale of the German soldier, supplied him with the latest word in radio reception. It is a three-band "morale receiver," vaguely similar to R-100/URR U. S. Army "morale" set, and was distributed to the soldiers for their entertainment.

The receiver was "liberated" by an 8th Air Force member and given to Sgt. Joseph Ferrara of the U. S. Army Infantry. It operates on either dry cells, wet batteries or 120 volts D. C., and is housed in an Army cabinet, portable style. When it is considered that the Germans have worked with "ersatz" materials for so long and have found them so "satisfactory," many features of its design are noteworthy. On the other hand, there are more bad points than good from the customary American standpoint.

The speaker has an unusually large magnet, when its total size is considered. The cone is approximately 6 inches, and the magnet is 2 inches in diameter and 2 inches in depth. The cone is supported by an "independent" spider such as has been found on some of our speakers. Adjustments in centering are accomplished on the outside, by means of two bolts fastening the spider to the speaker frame. A dust cover is placed over the speaker. This is nothing more than a piece of cloth, wrapped twice around the frame and tied in the rear. The voice coil leads are covered with what appears to be silken braid, and are brought through a rubber bushing or grommet. This is radically different from our standardized method of bringing them to insulated lugs on the speaker frame and then extending another pair of leads to the output transformer. The German method seems fraught with disaster, for, since the leads are exposed, a slight pull or accidental tug on them might carry the voice coil out of the cone to a place where it could readily be examined visually for defects in construction!

All Values Indicated

All condensers and resistors are marked with their values. This is considerably better than the system now in effect here (as has been brought out in numerous articles). On the other hand, there is an attempt in this construction to use altogether too many chassis. The electrolytic condensers are mounted on an independent chassis, as are the trimmer condensers. The bracket on which the electrolytics are mounted is easily seen in the rear-view photo. An entire network of condensers and resistors for several circuits is mounted in a little sheet-metal case. Leads to the proper circuits are then brought out through bushed holes in the sides of the cans. While this might facilitate assembly it does nothing towards making servicing any easier. Trimmers for all circuits as well as the padder condensers are all mounted on one strip. This includes the trimming condensers normally found on the top of the variable condensers in our receivers. The R.F. and antenna coils are mounted on the back of these strips. All coils in this receiver are wound on what appears to be plastic or possibly polystyrene forms, and are all tuned with an iron core (permeability tuning). The variable condenser is enclosed in an aluminum can, possibly. This tends to prevent tampering with the condenser and at the same time, both shields the variable condenser and protects the plates from possible damage. A fibre or plastic chassis is used instead of a metal one.

Wehrmacht radio vacuum tube - RF Cafe

One of the metal tubes from the receiver.

Removal-proof terminal screw - RF Cafe

Fig. 1 - This connector is absolutely secure in position once inserted and screwed down tight. The shell is crimped in near the top (see notch) thus making impossible removal of center screw.

The I.F. coils are wound on plastic forms. Low-temperature-coefficient condensers similar to some of American manufacture are mounted on a terminal strip inside of the can and connected across the primary and secondary of the coil respectively. These are fixed condensers rather than adjustable, as our I.F. trimmers are. The coils have an iron core in the center which can be adjusted through a hole provided for this purpose in the side of the can.

The can itself is made of heavy-gauge aluminum and is fastened by in an unusual manner. A slot is cut in the top of the can to accommodate a semi-circular strip of fibre. This in turn has a small rectangular slot cut into it. A fibre wedge is inserted into this slot and driven in until the can is fastened securely. The good feature of this is its easy accessibility. Just knock out the wedge, and the I.F. coil is available for inspection. This same wedge principle is used throughout as a convenient method of fastening without the use of nuts and bolts, and it is applied to the battery plugs as shown in the illustration., Fig. 1. As the knob is turned in, after the pin plug is inserted into the battery terminal, the wedge spreads the sides of the split banana plug, forcing them into tight contact with the sides of the battery terminal jack. The entire set can be lifted by this plug once the connection is tightened. This would seem to constitute a considerable improvement over our conventional snap-on buttons, binding posts, etc.

The tubes are the most interesting feature of this set. They are metal tubes roughly similar to ours in appearance, but approximately one-half the height and twice the diameter. The pins, as can be seen in the diagram, are of the locking type, yet the tubes are surprisingly easy to remove. This is accounted for by the fact that they also employ a wedge principle. They are tapered gradually instead of sharply as in the locking pin on American octal tubes. The tubes are mounted on felt cushions to protect them from shock, as can be seen in the photograph.

Wehrmacht radio vacuum tube sketch - RF Cafe

Fig. 2 - Wehrmacht tube. B - Glass insulating bead. C - Upper platform. D - Lower platform. D. - Metal-to-glass header ring. E - Lead to interior elements. G - Shell. H - Copper tube shown crimped after sealing-off.

An unusual feature is the total lack of glass in the tubes, with the exception of the seal of the pins to the base. Fig. 2 shows the method. This system has been used in special American war-time tubes, but is not yet commonly employed here. The tubes are evacuated after the assembly of the entire tube has taken place, with the exception of basing. A copper tube is brought out from the base, and the evacuating pumps attached to this. The air is then apparently pumped out and the copper tube sealed and crimped. A metal deflector plate is welded to the top of the inside crown of the tube. The elements, as is common in European manufacture, are laid on their sides, in contrast to our method of standing them up.

The line is fused in all cases, but the customary interlocking switches are conspicuous by their absence. A giant loop antenna is enclosed in the back cover of the "box" or cabinet.

Band coverage is from 15 to 50 meters; 200 to 550 meters, and 800 to 2000 meters, in addition to provision for phonograph attachment on the side of the carrying case, and a phono position on the band-change switch.

The dial is unusual in comparison to our dials. All stations are listed by the names of the cities or towns of origination. Calibrated markings on the top and bottom in meters merely serve as indicating devices rather than dependent tuning markings. The dial is made of glass. painted black on the inner surface with cut-outs where the station indicator windows appear. It is backed with a white drop, for easy reading. The grille cloth on the speaker is of a cream color which contrasts sharply but neatly with the black plastic trim and dial contrasting almost ludicrously with the drab, army-gray field case.

 

 

Posted August 2, 2021

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