Performance of restored Wehrmacht Radios

[Yuri D.]

Here's an interesting example of a repair saving an original component. In this Ukw.E.e, a resistor's end-cap completely came off. The resistor of course was not functional, so I just gently tugged on the end and the whole cap came off. What I did was to shave off a few bits of solder and put them into the end-cap. I then connected the end-cap to the resistor body, pressed them together, and heated up the end-cap with a soldering iron. The solder melted inside and fused the two parts together. Resistance measured perfectly on it after that. That wasn't the only repair necessary on that receiver, but it looked perfectly mint-condition on the outside, and had 4-5 cold solder joints, 2 bad caps, and this resistor wrong with the set. After all that was restored, it had to be tuned with a signal generator, my ear and a spectrum analyzer to get the best resonance curves possible:

[Funksammler]

Another thing to consider is that the performance of the sets is influenced by the type of antenna, the environment in which they operate and power supplies used. Yuri's Ukw.E.e for example would be operated within a tank with a bunch of noisy Umformer running on a 2 meter rod antenna, so I suspect noise levels of the receiver are not realy as relevant. If the tank was moving, I suspect only the strongest signals could be read.

Did you know that even the movement of the tracks could introduce static? The Sd.Kfz 250/251 carried a health warning that the Fuspr.f may not be usable on surfaced roads because of the static caused by the tracks.

regards,

Funksammler

[Quatsch]

Another thing to consider is that the performance of the sets is influenced by the type of antenna, the environment in which they operate and power supplies used. Yuri's Ukw.E.e for example would be operated within a tank with a bunch of noisy Umformer running on a 2 meter rod antenna, so I suspect noise levels of the receiver are not realy as relevant. If the tank was moving, I suspect only the strongest signals could be read.

Did you know that even the movement of the tracks could introduce static? The Sd.Kfz 250/251 carried a health warning that the Fuspr.f may not be usable on surfaced roads because of the static caused by the tracks.

regards,

Funksammler

That's interesting, thanks for bringing that up. Using fm, or at least having a noise limiter in an am/cw receiver would help in the noise department. Also, I suspect these radios were designed with the range criteria for the high hf and vhf gerat being only a few km at most, especially considering a 6ft antenna.






Yuri said;
"Here's an interesting example of a repair saving an original component. In this Ukw.E.e, a resistor's end-cap completely came off. The resistor of course was not functional, so I just gently tugged on the end and the whole cap came off. What I did was to shave off a few bits of solder and put them into the end-cap. I then connected the end-cap to the resistor body, pressed them together, and heated up the end-cap with a soldering iron. The solder melted inside and fused the two parts together. Resistance measured perfectly on it after that. That wasn't the only repair necessary on that receiver, but it looked perfectly mint-condition on the outside, and had 4-5 cold solder joints, 2 bad caps, and this resistor wrong with the set."





I've seen the caps on similar resistors employed in American consumer grade antique radio do the same thing, the cap falls off after a few decades of heating and cooling, to be either crimped or soldered back into service. It also makes me wonder how effective sabotage would be on such resistors, just enough contact pressure to pass their first inspection, then a few temperature cycles and jars and jolts from travel and presto no more resistor.