Heliradio

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HELIRADIO - Gerätebau Hempel KG
(VEB Gerätebau Limbach)

logo
legal form Limited partnership
founding April 1, 1950
resolution December 31, 1984
Seat Limbach-Oberfrohna , Germany
Branch Audio technology manufacturer

Heliradio ( Gerätebau Hempel KG ) was a producer of radio receivers, loudspeaker boxes, sound studio equipment, color television assemblies and medical equipment in the GDR . The company was based in Limbach-Oberfrohna in Saxony, which was also given in the abbreviated form of the company logo: HE mpel LI mbach .

history

The company Gerätebau Hempel KG was founded on April 1, 1950 by the engineer Bodo Hempel (born October 14, 1919 in Leipzig, † March 22, 1990 in Limbach-Oberfrohna) and started repairing radio and household appliances. In 1951 the first radio receiver appeared, the 51W, followed by the 53W Kadett, which appeared in 1953. The devices were initially only sold under the name "Heli Radio", but this changed in the early 1960s and the devices were labeled under the name Heli-Radio or just Heli.

Until around 1960, the products were designed by Hempel himself and developed by Erhard Gränitz. This changed when Karl Clauss Dietel and Lutz Rudolph got in touch with Bodo Hempel at the Leipzig trade fair in 1960. The two freelance designers were commissioned to design the device and also designed the new logo . They were also responsible for exhibition stands, promotional graphics and work environment design. In 1965 Martin Viohl took over the technical management and later Klaus Dietz became head of the development department.

For the Radio and Television Central Office (RFZ) in Berlin, among other things, special listening devices (loudspeaker boxes) were developed, but the electroacoustic development and production was also carried out for cultural institutions, theaters, opera houses and the private sector.

Until 1972, "Gerätebau Hempel" was a limited partnership , with Bodo Hempel and the state German investment bank as limited partners and therefore a company with state participation . When Bodo Hempel left the company in 1972, the company became a state-owned company and thus became " VEB Gerätebau Limbach" and part of VVB RFT Rundfunk und Fernsehen Staßfurt. In 1984 the company was finally completely taken over by VEB ELFEMA, Elektro-Feinmechanik Mittweida. The former VEB was now part of the ELFEMA company and was run as "BT Gerätebau Limbach". As part of the Kombinat Rundfunk und Fernsehen Staßfurt and therefore also part of the RFT manufacturers' association , most of the products were marked with the RFT logo.

After the German reunification , ELFEMA became a GmbH in 1990 and from July 30, 1993 all parts of the company were either privatized or dissolved. As early as 1990, Bodo Hempel tried to get his former company back, but this ended with his sudden death.

Logo

Until the company logo was redesigned in 1960 by Karl Clauss Dietel and Lutz Rudolph, the company logo consisted of a triangle with the words "Heli Radio". The newly designed company logo is derived from the symbols for antenna and earth - two arrows - which enclose the negative of the letter H (for Hempel), which was later replaced by the well-known RFT logo when it was transferred to BT Gerätebau Limbach .

  • Company logo until 1960

  • Company logo from around 1960

Audio products

Tube devices

  • Single circuit receiver Perkeo
  • HELI 51W
  • "Sea ranks" admiral, cadet, ...
  • Sonor and Sonorett
  • RK 2 including many housing variants
  • Module series 66: RK 3, RK-STEREO, RK-TUNER, RS 5
  • RS2 and RS2F

Hybrid devices

RK4

The RK 4 device marks the breakthrough in transistor technology at HELIRADIO. It is the preliminary stage to the rk 5 sensit . The arrangement of the control elements corresponds to that of the rk 5 sensitive (balance control for the first time on the front) while the NF part is completely equipped with transistors. Tried and tested tube technology is only used in the HF section.

Transistor devices

rk5 sensit and loudspeaker LK 20 sensit
rk5 sensit

Both the rk 5 sensitive device and the LK 20 sensitive loudspeaker were designed in 1967/1968. Series production started in 1970.

The RK5-Sensit formed the basis of all subsequent devices in the rk series up to the rk 88, which were only slightly modified in the subsequent models, both in terms of the electrical structure and the external shape. The device was extremely modern at the time it was launched. Electronic station search and (almost) full use of silicon transistors were an absolute novelty on the GDR market.

The fact that such a device was developed and successfully sold by a "semi-state company" certainly caused a sensation at the political level. The fact that a number of semiconductors had to be imported for production meant that the devices could never be delivered in sufficient numbers despite their price. The price was well within the scope of what had to be paid, for example, for devices such as Rema Adagio or Andante, although these were manufactured with inexpensive germanium transistors and a large proportion of standard components.

From a technical point of view, the coordinated RF pre-stage in the AM area, which was unique in the device range of the GDR industry, is remarkable. It gave the device excellent remote reception properties. This was particularly important in the areas of the GDR that were beyond the reach of West German VHF transmitters ( ARD , RIAS )

rk7 sensit

The only germanium transistor of the rk5 sensit is replaced by a Soviet type of silicon. The audio output stage was revised, the FM tuner could be equipped with DDR transistors.

rk8 sensit

The rk8 variant was provided with two additional loudspeaker sockets, which were suitable for connecting two “pseudo-quadro” loudspeakers.

rk88 sensit
rk88 sensit

The first integrated circuit in the rk series appeared in the rk88 - the A290 was built into the stereo decoder (DDR replica of the MC1310 / XR1310). The rk88 sensitive IC variant was given the first thorough redesign through the use of integrated circuits. FM-ZF, AM-HF and -ZF, tuning electronics / display and LF pre-stages were equipped with ICs. This made the VHF tuner the only assembly that had not undergone any changes over the entire production period - apart from the replacement of western imported semiconductors with those from the GDR or the brother countries as soon as they were available.

rk90 sensit cubus
rk90 sensit cubus

Work on the design of the rk90 cubus took place from 1984 to 1987. (When the electronic development began / ended has to be added.) The rk90 sensit cubus had a completely digital control and was dependent on the use of a remote control. There are some pre-series copies, there was no series production. The formerly private company had meanwhile been completely expropriated and incorporated into VEB ELFEMA Mittweida . Obviously, under these conditions it was no longer possible to develop and manufacture a product that withstood the then state of development co-determined and international comparisons. The coup that was achieved in 1970 with the rk5 sensit could not be repeated. The long development time and the existence of functioning patterns indicate that the start of production was hindered, presumably because the management did not want to bear the risk associated with the innovation. One of the rare specimens can be viewed in the Chemnitz Industrial Museum .

Clock Heliradio

The first hotel radio with an integrated clock appeared in 1964. The radio receiver was developed for the Interhotel Association and has a large round timer from Weimar electric. The broadband loudspeaker is attached to the front. The hotel radio receiver, released in 1969, has a large rectangular clock and the speaker is floor-mounted and radiates downwards.

speaker

Ball box LK 22 - prototype

In addition to the radio equipment, high-quality loudspeakers were also manufactured at Hempel, often they were derived directly from corresponding product lines. It was not only developed and produced for radio and television, but also for the private sector.

Studio box K12-Studio

The closed studio box with veneered chipboard housing, built in 1966, has a full-range loudspeaker from Schulz, model KSP 130k, with a diameter of 13 cm and a nominal output of 5 watts. The passive equalization of the loudspeaker with a suction circuit, which is located in the loudspeaker housing, is remarkable. The slightly inclined arrangement of the speaker in the housing is also interesting.

Studio box K12-Studio with amplifier

The K 12-Studio K12 Studio with amplifier has a removable amplifier section with 45 watts of power on the back. The active version of the K12 is also equipped with passive equalization of the loudspeaker and the input is symmetrical, the 1.55 V usual in a studio is required. The box was often used as a control monitor on television in the GDR.

Studio box VS1-32 Z 132 - Z132 / 1

The active studio monitoring system "VS1-32 Z 132" from 1969 was created by combining the VS1-32 tube power amplifier with the L40 compact box . The KSP215 broadband loudspeaker with a diameter of 21 cm and a power output of 12.5 VA came from the Berlin-based company K.Schulz. Over the years the VS1-32 tube amplifier was replaced by the VS132 transistor amplifier and the active loudspeaker box was now sold under the model name “Z132 / 1”.

Ball box K 20 sensit

The spherical box made of cardboard strips and coated with rough plaster has a diameter of 330 mm and was first presented in 1968 at the Leipzig autumn fair. Originally it was to be given the model name K20 , but was already offered in 1971 as “K 20 exclusive” and in 1972 as “K 20 sensit”. The spherical box is equipped with a broadband loudspeaker model KSP215, with foam surround and tweeter cone, and has a built-in frequency response correction element, the nominal load is 20 watts and the transmission range is from 60 to 20,000 hearts. The housing was manufactured by a cardboard box factory in Wurzen, the final assembly was also carried out on behalf of Hempel at VEB Statron Fuerstenwalde, where the name K 20 sensit was also created. There was also the K 20 E ball box with a case made of fine wood and a diameter of 340 mm.

Ball box LK 20

The "LK 20", created in 1974, is identical to the "K 20 sensit", but its housing is made of polyurethane foam (PUR rigid foam).

Ball box LK 6

The "LK 6" ball box was offered for the first time in 1976 and, like the K 20 sensit, was made of cardboard with a rough plaster coating. They were available with a support ring for a shelf or optionally with a device for wall mounting. Its diameter is 220 mm and has a full-range loudspeaker L2301 with 6 watts of power, the transmission range goes from 75 to 16,000 hearts with 87 dB.

annotation

After the spherical shape for loudspeaker boxes was established on the market, it was also adopted by other manufacturers. In the GDR, however, the ball boxes were also subject to the usual drive towards standardization. That is why it is not always possible to infer the manufacturer directly from the appearance and designation. The production of certain models was also relocated to other RFT companies. For example, the K 20 sensitive was also manufactured in the VEB Statron Fürstenwalde .

Shaping

The devices from HELIRADIO are characterized by the unmistakable signature of the designer duo Dietel / Rudolph , who succeeded more and more in developing an independent form. This was shown for the first time with the rk5 sensit, which left behind internationally recognized design templates and it continued with each new device. The Programat device is considered a special development and design achievement (with station search system, prototype 1968); also the studio speakers VS 1 , the studio monitors K12-Studio and the subharchord for synthetic sound generation.

Museums

HELIRADIO products are in the collections

particularities

Amplifier HS-1 (ca.1961)

HELI products can be described as typical of the "centralized throttled" innovative strength of the GDR industry, especially of the medium-sized companies that were still active until 1972.

Inside view of HS-1

They combine creativity with the obvious compulsion to improvise. Two examples (HS-1 and Subharchord) should describe this:

HS-1

  • Multiple channels (stereo), including a separation into the low and mid-high frequencies.
  • Separation into a small high-midrange and control unit and a large bass unit (a large loudspeaker in a large box / baffle is required for bass reproduction anyway).

The stereo amplifier HS-1 (picture) is the first example of how devices with forward-looking properties were created despite the most economical use of materials.

Particularly noteworthy is the bass output. Although the output power of the HS-1, around 2 × 2 watts, does not even come close to today's standards, it was able to generate a volume sufficient for home use. This was achieved through the possibility of connecting an additional bass amplifier. It is fundamental that the spectral distribution of conventional music and speech reproduction only requires a low output power in the range above 300 Hz.

The HS-1 anticipated all the features that characterize today's modern sound systems. In the early 1960s, HELI delivered a technology that only became established on the market much later under the name of subwoofer . The entire HS-1 system represented high-end quality in its time.

The device was improvised insofar as the construction was carried out as if one had a printed circuit board to accommodate the components. In fact, however, it is a PVC sheet with holes drilled into it, through which the connecting wires of the components were then inserted. Because the conductor tracks were missing, the connections of the components on the underside were connected directly in the conventional manner. The advantage of this solution was that it was possible to dispense with the usual solder lug strips as component carriers and still achieve a stable but also space-saving structure.

This is how Heli started its introduction to printed circuit technology. Later versions of the HS-1 have printed circuit boards in the form known today. The components were not at all well suited for this technology (the connections of the resistors were formed by sheet metal strips, as is usual with conventional wiring). For circuit board technology, however, it is better to use wires with a round cross-section; this makes it much easier to produce more reliable soldered connections. But the Hempel company did not let this deter them and dared to take the step into a new technology. (With success, as evidenced by a number of HS-1s still in use today.)

Subharchord

The subharchord - a device for synthetic sound generation - is another example of the innovative strength of the HELI company, which could only be slowed down by the real socialist political bureaucracy.

literature

Web links

Commons : Heliradio  - collection of images, videos and audio files