Renovation object 2009
Renovation object 2009
Corrosion on chassis,and paint corrosion.The vibrator must be opened and adjustet.Condensatores inside power must be changed.New tube in transmitter/receiver RL2,4T1. Demounting all parts to get the front free for paint and corrosion.
Feld Fu.f (White mark ) Used of DAK (Deutche Afrika korps) and the Eastfront.
Feldfu.f (28-33Mhz 10meter band) have a lot more coil-turns on the oscillator and antenna output coil.As seen on pictures.Then the front channel switch is formed othewise.The antenna connector on the box is bend backwards a lot more than on "b" and "c".On the feldfu,b and c (92-108 and 130-136Mhz) the antenna are a quarter wave with low impedance on the antenna base. On the other hand, the "f" working on 33Mhz,the antenna resonating coil in the bottom would be disturbed from the soldiers helmet,as it have a high "Q" high impedanse right over the coil..Orginally the antenna for this frequency should be ca 2,5m long. Not practical.For shorter distances it work with the 72,5cm " b " antenna direct on the ant base.The pictures show the ant mounted on a Feldfu f box.The freq tuning scale have no "channel" lock as Feldfu b and c.It is tuning like a old radio.
The power filter capacitors was faulty,and the vibrator GL.2.4 was not opened.It start vibrating,but giving no voltage out to the radio.After opening it with special tools the contacts on high power side was clogged with corrosion.After cleaning and adjustments,it work as new. The capacitors in the high voltage "Modul" was changed with new.The voltage should be,with all tubes out, measuring, ca 166 volt Dc.The accu 2,60v. Test the power with a 12kohm resistor from C34+ to ground. It will flow 12ma and the voltage drop to 142v. (ca 1.5w).The main transformer U3 coil for the negative voltage to the modulator, (-5 to 6 volt) was broken.Water corrosion eaten off the end wire.New coil 300t 0,3cu was wind on the outer part of the transformer core. Then I obtained the wanted negative voltage to the modulator.
Feld Fu f. finished, painted and adjusted
The Feldfu f. finished and adjustet,ready for the field action.The main box would be like the feldfu b,but the antenna connector on the top of the box are changed.The connector as told before,is bend a little backward.It is done for the high Q coil on the antenna bottom.If not,the soldier helmet will readjust the coil (capacity from the iron helmet).
Batterypack 1 piece, to the Feldfu series radios.The battery measurements are likely the same as the Russian (Light green) NIFE/NICAD as the German original Feldfu battery. Original 2,4vdc and 28Ah,and the Russian 2,4vdc and 26ah.It places nicely into the battery compartment.
DAK
The antenna for feldfu f (freq 30Mhz band) should, as a quarter wave, be around 2,5m long. This is not practical in the field. The main ant is 90cm long steelblade type. In the bottom it is a antenna "shortner resonator coil" to let is be the right impedance . The antenna is "bend" backward on the radio box. This is done for the soldier helmet not to disturb the high Q antenne coil. All metall parts should be ca 4-5cm away from the coil. Communications in the field around 1 km, you do not need the bottom coil. With the coil around 2-3km or more. Using the radio in the nearfield as 100-250m it works only with the coil alone. The frequencies around 30-40mhz works best in flat field and in heavy wood terrain.The reflections is low. Feldfu b and c have mutch more reflections in the hilly terrain, and works better in the mountains, and in the city. So one, the Feldfu f was for the most in use in the eastern front and in the deserts.
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