Herald

The first product launched was the RP10 Herald. In common with many of their 1960s designs, this was built into a wooden case covered in leathercloth, with foam padding under the front and rear panels and a turntable to enable the set to be rotated for best reception (the internal ferrite rod aerial being highly directional). It featured a large (5 inch by 8 inch) 30Ω loudspeaker, and was powered by two PP9 batteries. Initial sets used Ediswan transistors; later sets used Mullard devices, including the AF117, which unfortunately went on to suffer from tin whisker formation within the encapsulation.^[4]

The Herald was an AM only set, covering the medium wave and long wave bands. A three position tone control switch was provided. The radio was initially available in beige or deep red with brass trim, but towards the end of the run, alternative colours were offered (blue with chrome and white trim, or black and grey, also with chrome trim).

The next Herald, the RP30, retained the same loudspeaker and grill, but had a restyled cabinet that retained the padded leathercloth, which was available in charcoal black, blue or red (the latter with brass trim). The electronic design was revised, and the audio amplifier was rather more complex, incorporating rotary bass and treble controls. Coverage was MW and LW as before, but a version including short wave (16.5 to 50 metres) was offered (the RP31SW). Later, another version offering Marine Band (70 to 200 metres) in addition to MW and LW was released (the RP32), but this sold in relatively small numbers, and few exist today. These sets continued to use the Mullard AF11x-series of transistors.

The RP35 looked quite similar to the RP30, but the top panel (containing the controls and tuning scale) is quite different in detail if not layout. The available colours were the same as the RP30 Herald. Electronically, these are quite different from the previous models, introducing a separate transistor for the oscillator, and a new, more compact layout for the IF PCB. The audio amplifier is improved while the component count is reduced - now the loudspeaker is 15Ω. Initially these used the Mullard AF117 transistors, but switched over to using silicon BF194 and BF195 "Lockfit" transistors from serial number 19001.^[5]

Another AM Herald, the RP82, was introduced towards the end of Hacker's existence, but these are very scarce indeed. Electrically, they are based on the very basic AM-only RP70 Ranger.

VHF Herald

The RP37 VHF Herald looked like a third-generation Herald, but the presence of a telescopic aerial indicated that this is an FM-capable receiver; indeed it was an FM-only radio. Like most Hacker sets from the 1960s and early 1970s, this set used two PP9 batteries. They were available in the same colour choices as the RP35 AM Herald, and there was a variant with a revised scale in royal blue that incorporated the Open University logo in place of the local stations. The terms of this arrangement are presently unclear.

Mirroring the changes in the RP25A Sovereign described below, the later RP37A VHF Herald had a revised FM tuner; recognisable because it has a clear plastic cover rather than an aluminium enclosure. At a similar time, the loudspeaker was changed from a grey painted unit made by Goodmans to a silver-framed Celestion or a unit supplied by Elac which was recognisable by the large ceramic magnet assembly. This latter loudspeaker was only ever fitted to the VHF Herald.

Sovereign

This was Hacker's premium portable model, featuring AM and FM reception, and the name was used for four generations of the receiver. The first three versions featured separate tuners and IF stages for the AM and FM sections. The first generation, the RP18 Sovereign, was released in 1964, and was slightly larger than the contemporary Herald. The case was leathercloth-covered wood with padding for the front and rear panels, and was only available in charcoal black. The same large loudspeaker was used. The FM front end was bought in from German company Görler, and the rest of the tuner sections used Mullard AF11x-series transistors. User-adjustable station markers were provided to indicate the position of three favourite stations - but as these could only be moved over the lower half of the FM band (which only extended to 101 MHz), they were intended to locate the three national BBC services available at the time.

The next generation, the RP25 Sovereign II, was very similarly styled, with the external differences being most noticeable on the top panel. This model was available in charcoal black and blue. The audio and AM sections were identical to the third-generation Herald, and the FM sections were a new design with the FM front end now made in-house; the FM and audio sections went on to appear in the RP37 VHF Herald. Initially, AF117s were used in the AM tuner, but from serial number 13001, BF194/195s were adopted^[6] (the FM sections used these silicon devices from the outset). This set introduced an ISM (inter-station muting) function for the FM band, operated by a switch that also enabled the AFC function, which eliminates the loud noises typically heard when tuning across the FM band. There are now four station markers, which can be placed anywhere within the band (which still only reached 101 MHz).

The RP25A had a redesigned FM front end; the new tuner is distinguishable by the clear plastic cover rather than the earlier aluminium case. At a similar time, the grey-painted Goodmans loudspeaker is replaced by a model made by Celestion - the later is recognisable because it has a painted silver frame and magnet. At some point towards the end of the RP25A production run, an 18 volt DC input socket is added to the left hand side panel. And finally, the RP25B uses a different FM IF PCB, incorporating an integrated circuit and ceramic filter. During the RP25A run, an all-white version was released. These are relatively uncommon today, and good examples can sell for higher prices than otherwise similar black or blue sets.

Next, in 1973, the RP72 Sovereign III is released with very different styling compared to the previous models - featuring teak side panels and extruded aluminium for the loudspeaker grill and top control panel assemblies. Separate AM and FM tuners are retained, while the audio stages gain a new pre-amplifier that incorporates passive Baxendall tone controls. The loudspeaker is slightly smaller at 7 by 5 inches, and is now supplied by Peerless. The set is powered by eight 1.5 volt "D-cells" rather than two PP9s. Earlier models had a DC-input socket on the back; later models incorporate a mains power supply and are designated RP72MB. While the majority of these sets are restricted to 101 MHz on the FM band, later models were able to tune to 104 MHz. The ISM function was dropped, but switchable AFC remains. A common problem with these sets concerns the screen printing on the top panel, which can wear away.

The final Sovereign - the RP77MB Sovereign IV - was rather different. It used simpler and cheaper circuitry that no longer had separate AM and FM sections. The case was somewhat larger because it was originally designed to accommodate a cassette mechanism; the RP77MB Sovereign IV was a radio-only version of the RPC1 radio-cassette recorder. The styling was similar to the previous model, with a black anodised finish to the aluminium components. The turntable was dropped for this model. As with the Sovereign III, operation is from eight D-cells or the mains supply, and MW, LW and FM (to 104 MHz) bands are covered. The amplifier circuitry is simpler than the Sovereign III; in fact, it's electrically very similar to that used in the Sovereign II - though with some component changes. The loudspeaker is a 5 by 8 inch model made by Elac.

Super Sovereign

There was a variation of the third-generation Sovereign called the RP75 Super Sovereign. This took the basic RP72 Sovereign and added two short wave bands - the only Hacker set to include both FM and SW. Coverage was 10.9 to 33 metres and 27.5 to 89 metres. Electronic fine-tuning (band-spread) was provided, and switchable ISM returned to the FM band; separate switches are provided for ISM and AFC, unlike the Sovereign II where these functions were combined on one switch. A signal-strength (and battery test) meter was provided. Echoing the development of the RP72, a mains power supply was added (the RP75MB), then the FM coverage was extended to 104 MHz. With the MB models, an ATU (aerial tuning unit) was included to improve short-wave reception. The speaker fitted to the RP75 and RP75MB was the same as the RP72, but with a larger magnet.

Hunter

The RP38 VHF Hunter was released in 1969, and was intended to be an "economy" set. It had MW, LW and VHF coverage. The cabinet was also cheaper to make and lacked a turntable. Initial models used the same 5" by 8" Goodmans loudspeaker as the contemporary RP35 Herald/RP25 Sovereign, but a model from Elac quickly replaced this.

An updated version followed a year later: the RP38A. This added bass and treble controls, using an amplifier that was electrically very similar to that in the RP35/RP25. This model was in production for many years, and went through several cosmetic changes before production ended in 1976. Initially available with side panels in finished hardwood or covered with black leathercloth, and black leathercloth covered front and rear panels (with no padding), the grill was thin aluminium perforated sheet which picks up dents rather easily. In 1973, a new grill was introduced - the same as the Sovereign III "family" - which was a heavy and thick aluminium extrusion. At some point afterwards, the handle is changed to a three-part unit that matches the rest of the Hacker range, and then towards the end of the run, the silver tone control knobs are replaced with black plastic versions. All versions of the Hunter have an FM band that is limited to 101 MHz (and non-switchable AFC).

The Hunter remains a popular set, despite its original "budget" status, and frequently achieves high sale prices on auction. The Elac loudspeaker provides a good audio performance, many enthusiasts preferring it over the various Sovereign sets.^[7]

Mayflower

In 1962, Hacker released the RV14 Mayflower; an FM-only valve table radio finished in striking veneers. Unusually for a Hacker, this set had coverage to 108 MHz - the FM front end was supplied by Görler. The audio sections were based around a pair of ECL86 triode/pentode valves that operated in push-pull, delivering around 7 watts in ultra-linear mode to a large (10 by 7 inch) loudspeaker. An EM84 "magic eye" tuning indicator valve was used.

The RV20 Mayflower II was released in 1963. This was electrically very similar, but had a very differently styled cabinet. The FM tuner was a different model that had reduced coverage to 104 MHz, but added an AFC function.