From the PLATH archives: Our DFP 5300 was the FIRST broadband direction finder in the world and appeared in 1990

In this year, he will turn 34. The DFP 5300 developed by PLATH in 1990 was the world's first broadband direction finder (photo). Until that point, it was only possible to determine the direction of individual radio signals. Due to a series of unique innovations, it became possible to simultaneously direction-find multiple signals on different frequencies and display them in an overview, in a so-called direction-finding and overview spectrum.

However, back then, broadband was understood to be only a 200 kHz instantaneous bandwidth with a total covered frequency range of 6.4 MHz. In comparison, the current state of the art is at least 80 MHz instantaneous bandwidth and a frequency range of at least 6 GHz. The DFP 5300 consisted of an advanced multi-channel receiver with a well-equipped computer for that time, featuring a 68000 processor from Motorola, also used in home computers like Atari ST or Commodore's Amiga. This central processor was complemented by so-called transputers programmed in the languages OCCAM and Assembler. The device's required height of 18 so-called rack units (RU) almost filled an entire rack; the synthesizer alone took up three rack units. Nowadays, a radio direction finder requires hardly more than 4 RU, and a synthesizer is little larger than a cigarette box. A PC was used to operate the direction finder and display the spectra, with the bearings and temporal progression of signals shown in a waterfall diagram and an instantaneous spectrum.

Until the mid-2000s, diverse trials provided experiences that could repeatedly surprise: for example, a high detection probability for frequency-agile signals, known as hoppers, could be achieved in scanning mode. The trick was to measure the dwell time during a frequency hop not in the time domain but in the frequency domain based on the amplitude profile, which followed an SI function—a function with a sine of x divided by x.

Interesting side notes about the record device include setting the year 1967 as year zero for the file system, as the two programmers of the file system were born in 1967. Additionally, program code from the manufacturer of cigarette vending machines HAUNI was included, which sometimes led to bizarre messages that would be called "Easter eggs" today. One error message read: "Please refill cigarette tubes." The device remained "top of the class" for many years before successors took over. However, due to decades of collaboration with the most demanding customers, PLATH continues to be a leader in radio direction finding.

With the direction finding of each individual signal in the range of 0.5 to 30 MHz, the current model DFP 5135 is still a world-class direction finder. Its features include high frequency resolution of 125 Hz, a high intermodulation-free dynamic range (IMFDR3 > 105 dB), and a blockage-free dynamic range (140 dB/Hz). Additionally, it offers multi-user operation (simultaneous access by the system and up to four users) and the ability to use up to 120 virtual narrowband receivers in one direction finder.

Furthermore, we would like to mention the new V/UHF direction finder DFP 2175. Feel free to inquire about its incredibly outstanding values.