Grosse 1.5 kW Kurzwellen-Funkstation (High Power 1.5 kW Shortwave Station), G1,5K or B-Station; developed by C.Lorenz AG.
The High Power Shortwave Station G1,5K, also called „one and a half K“ or „grandmother“ by the signalmen, was the second high power shortwave wireless station used by the Swiss Army.
The amplitude-modulated shortwave station with 1.5 kW output power was developed by the C. Lorenz AG in Berlin - Tempelhof in around 1935 and was construced in 1937 - 1943 by the Standard Telephon & Radio AG in Zurich, the Swiss branch of Lorenz.
For many years, the G1.5K was the backbone of command radio traffic between general staffs of the field corps and in the Air Force, where the station was known as B-Station.
SE-302 Station Equipment: Review of the station equipment of the different configurations.
The transmitter covers the frequency ranges 1090-1930 / 1930-3430 / 3430-4830 and 4830 - 6700 kHz; the dial accuracy is 1%o, a quartz crystal allows the calibration to 3000 kHz.
The station has a maximum output power of 1500 W in CW telegraphy (A1) and 500 watts in modulated telegraphy and telephony.
As a receiver in the first 14 stations, the battery powered two tuned circuit TRF receiver EO509/I built by C. Lorenz AG is used. Due to insufficient sensitivity especially in the more challenging reception mode Hell, in the stations with numbers above 15, the all-wave receiver "Uster"/E41 was used.
In 1956, the station G1,5K saw a major upgrade: with the new station receiver Autophon E-627 and the combination Telecrypto 53 / ETK, automatic encrypted teleprinter operation was possible. Wireless transmission often suffered from synchronization failures. The replacement of the station receiver by the Siemens E-311 / E-645 did not significantly improve the situation. Only with the introduction of the KFF58 with automatic synchronization, automatic encrypted communication was improved considerably.
At the time of the introduction of the G1,5K, not only telegraphy or amplitude-modulated telephony were standard operation modes. but also Hell teleprinting. The Hell teleprinter, developed by Siemens, transmits plain text as a quasi-facsimile transmission mode.
The technical requirements of Hell transmission procedure were high and transmission often suffered from disturbed shortwave propagation. The high demands on the operating signalmen were often not met, as they were civilan and not professionally trained telegraphists.
Therefore, during the „active service“ period in WWII, the Hell mode was abandoned and changed to automated high speed telegraphy Moser-Baer, as the Morse code knowledge and reading speed of the militia signalmen too often was insufficient. Although high speed telegraphy allowed the messages to be transmitted more quickly, the reading of the Morse code printed on paper tape also required good knowledge of Morse code. Well trained signalmen could read Morse code nearly as fast as it appeared on the paper tape printer. As experienced radio operators achieved resultes at least as good as automated high speed telegraphy, this operation mode was abandoned too.
The breakthrough was in 1955/56, when the station was equipped with the teleprinter ETK, developed by Dr. Ing. E. Gretener AG. In cooperation with the Telecrypto 53 even automated encrypted teleprinting was possible.
However, the synchronization of the decryption too often fell out of sync due to propagation disturbances, so the message had to be retransmitted. An attempt to improve these circumstances was the introduction of the Siemens E-311 shortwave receiver (E-645), with its superior single-sideband reception performance, with optimum frequency and antenna choice and with well trained station personnel, the situation improved.
When it became evident, that encrypted communication with the „lightweight“ SE-222 / KFF-58 was much more stable due to its outstanding SSB performance and automatic synchroneous operation, this equipment replaced the older high power station in most applications.
In the Transmitter one tube RS337 is used in the control circuit, two RS337, in the intermediate circuit, two RS329g in the RF final amplifier. Two RS282 and three rectifier tubes RGN2504 are used in the modulator and keying stage, two RS282 ans three RE084k in the (microphone) amplifier stage.
The technical principle of the various receivers are discussed in the corresponding articles.
The high power shortwave radio station G1,5K was developed in around 1933/34 by C. Lorenz AG, Berlin. It was manufactured by Standard Telephon & Radio AG in Zurich in 1935/37. A total of 34 (according to Ritter 27) stations were constructed and introduced as G1,5K with the signal troops and as „B station“ with the Air Force.
Three of the 34 stations were installed in fortresses.
According to the documentation „radio stations of the army“, the G1,5K station was assigned not only the designation SE-302 but also SE-305, the difference between the two designations is still unclear.
The G1,5K / SE-302 remained in service for decades and after several upgrades was only decommissioned in 1970 and replaced by the radio station SE-415. In the Air Force, the B-station was withdrawn after the transfer of aeronautical communication to the VHF band in 1946.