Fahrbar Leichte Funkstation 40 (Mobile Light Radio Station 40), FL40; manufactured by Zellweger, Uster.
To replace the „Tragbar Schwere Funkstation 18/25“ (Heavy portable wireless station 18/25) and the „Fahrbar Leichte Funkenstation 19/25“ (Light mobile wireless station 19/25), Zellweger AG, Uster developed a new wireless station covering the longwave and shortwave band in the years 1938 - 1940.
Still according to the doctrine of use from the twenties / thirties, the wireless station was designed on a single axis trailer to be pulled by another vehicle, it got the nickname „vegetables trailer“ from a kind of trailer used by vegetable farmers.
If mobile use on a trailer was impossible, for example if the station should be operated in a bunker, a command post or on a hill or mountain top without an access road, the station with the same components was used as Tragbar Schwere Funkstation TS40 („Heavy portable station 1940). Nearly all accessories were included, in favour of the troop which had to carry the station, the DF antenna for the receiver and the 10 m telescopic mast was omitted.
The entire radio station FL40 is housed in two single axis trailers: one is the „apparatus trailer“ with transmitter, receiver and the telescopic antenna mounted on the trailer, the other is the „machine trailer“ with a three phase generator driven by a petrol or an electric motor. The generator provides the necessary (plate) voltages, all antenna material is also stored on the trailer.
The station was powered by a petrol or by an electric motor coupled to a three phase generator, which provided the necessary 50 V 150 Hz voltage. A rectifier unid was used to generate the plate voltages of 1250 and 300 V for the transmitter and a solid state rectifier to generate the plate voltage of 120 V and heaters voltage of 6 V of the receiver and the accumulator charger.
An inverter is used to generate the plate voltage of the receiver E41 from the heaters accumulator power of 6 V, when the generator of the transmitter was not in use, or for remote control of the station.
Here find an overview of the components of the Mobile Light Radio Station 40.
The station receiver E41 is a battery valve all-wave receiver; at frequencies below 12 MHz, it acts as single conversion set and above 12 MHz as double conversion superhet; the frequency band selection is done with plug-in coil sets, similar to those found in the HRO.
The matching transmitter S-300 is housed in an almost „portable“ metal chest with side flaps for aeration and for the antenna connectors.
The transmitter covers longewaves 190-242 / 242-400 / 400-715 kHz and three shortwave ranges 1500-2300 / 2300-3300 / 3300-4500 kHz, a calibration crystal is used to calibrate the transmitter on 4000 kHz.
Refer to the pages of the components.
In 1938, there was an invitation of tenders to develop a „mobile lightweight“ radio station as a replacement for the „Mobile light radio station 19“. There were outlines of sets from C. Lorenz AG and Telefunken Zurich AG; but Zellweger, Uster submitted a suggestion matching all requirements, still mounted as required on a single axis trailer, prototypes of the set had a very good echo and after great effort the first production badge was delivered to the troops already in 1940/1.
The newly developed components like receiver and transmitter were not only used as FL40 („so-called Gmüeswägeli“), but electronically identical also as TS40 („Portable Heavy Station 40“), as KL43 (G-Station to replace the short-longwave station Telefunken and it's all-wave receiver „Uster“ / E41 was used as standard receiver in the high power stations until its replacement by the E-627.
98 units of the „Mobile Light Stations 40“ were ordered, in 1942 the station was equipped with additional antennas (L and T antenna) for ionospheric communication. The station was replaced by the SSB station SE-222 in 1961 and all station equipment was liquidated in 1971/72.
The 98 station were delivered 1939/43 and were used for command communication until 1958, the equipment was liquidated in 1971/72.