Part 2



Standard type of trimmer used in the Ukw.E.e. The top screw is soldered to a fine spray of silver metallic surface. This screw is connected to one of the bottom terminals. Between the two ceramic disks, is a metal plate which acts as the second part of the capacitor. Rotating the screw changes the capacitance from approximately 10 to 32 pF. This trimmer is present on many other German radios such as the Torn.E.b and the Kw.E.a.

The problem with these trimmers is that after 65+ years, the ceramic disks somewhat fused to each other, and if a screwdriver is used to turn the disk, the screw will SNAP its solder from the sprayed-on surface. Since the original solder job was an industrial process, it cannot be easily repaired at home.



In the top center of the photo, the red aligator clip is sending the sweep generator signal to the input of the HF tank. The red wire on the left side of the photo is connected to the control grid input of the HF amplifier tube socket. This tests the frequency response of the HF tank only.



Here it is at the bottom of the receivers frequency range.



And at the top of the frequency range.






At the bottom of the range after tuning. (best possible result)


At the top of the range after tuning (best possible result)



This is the mirror frequency response on the left.



The signal generator is producing a large 1 volt signal.



Here the heterodyne is being tuned. Note the red clip connected through the round hole conveniently placed on the box containing the local oscillator tank circuit. The screw driver is being used to tune the resonant frequency of the local oscillator, which is comprised of the tank circuit in question and Tube #4.



The red clip is connected to the frequency counter, which accurately reads 24.2083 MHz, which is almost exactly 3 MHz less than the generated HF frequency of 27.2 MHz. The intermediate frequency of the Ukw.E.e is 3 MHz.



Here is the same test of the receiver when set to the top of the frequency range at 33.3 MHz. The frequency counter reads 30.2804 MHz, which is 3.020 MHz less than the HF frequency. A deviation of only 20 KHz. Not bad at all.



Lead connected to the 2nd IF control grid.



Another trimmer. This one has a date (39th week of 1940)






Signal input is the control grid of the detector, and signal output is right after the 1st IF anode output.



3 MHz signal



The signal at 30 MHz produces a wide-band response of 12 mV. The response is 1.2 MHz wide.