Quote:
Originally Posted by CarbonMike
I wonder why GEC entered the receiver market, which was rather crowded in the 1940s/50s? Did GEC develop receivers before the BRT series, or was this a new venture? Did they continue to make receivers after this?
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I don’t know whether GEC offered a similar-specification professional communications receiver before WWII. But post-WWII it probably saw that there was a significant market for new such receivers amongst government and professional users, in contradistinction to the consumer and amateur markets, for which much military/government surplus equipment was available.
The GEC BRT400 was mentioned briefly in Wireless World (WW) 1949 January (page 14) and was the subject of a full test in WW 1949 May (page 171ff). Here are some advertisements from the 1950s:
My understanding is that the various suffix letter versions and the BRT402 differed from the original only in detail. All had the same basic circuit, of the standard-for-its-time single-conversion 2 x RF, 2 x IF form. Perhaps a standout feature was its amplified AGC system, which effectively used DC amplification (in a combined rectifier/amplifier stage) rather than say a side-chain extra IF stage as used by Marconi on some of its receivers.
The BRT400 series had a long production run of around 20 years, and was replaced by the RC410/R solid-state model, announced in WW 1968 February. So one assumes that it was a worthwhile exercise from GEC’s viewpoint. The RC410/R evidently had a long gestation period. It was mentioned in “Technical Topics" (TT) for 1966 July, then again 1968 January as only just having entered production, with a late change to cascode jfets in the RF stages. It was definitely of the transitional period, combining full synthesis with a valve-era topology, tracking-tuned RF section and double conversion with 1.6 MHz and 100 kHz IFs. It had two tuned RF stages, so effectively had a four-gang front end. Whilst this was common, perhaps even de rigueur for higher performance valved communications receivers, it was apparently rare in solid-state practice, where, if an additional RF “gang” was desired, it was done as a bandpass, either input or interstage, around a single RF stage. (The Eddystone EC958, EC964 and Marconi Hydrus provided contemporary examples of the bandpass approach.) The turbulence created by paradigm shift produces some interesting side effects.
The RC410/R was evidently caught up in the events of the time. In later 1968, following its 1967 acquisition of AEI, GEC took over English Electric (EE), with which came Marconi, a subsidiary of EE since the later 1940s, and Eddystone, a subsidiary of Marconi since 1965. So GEC had three lines of professional HF communications receivers, obvious targets for rationalization which was of course the Weinstock mantra. At the time, the Marconi and Eddystone lines had not been fully integrated, although Eddystone had been a supplier to Marconi since the early 1950s. But there were signs of co-ordination. The Eddystone EC958 had been designed with marine main receiver applications in mind, and the marine version, in the guise of the Marconi Nebula, was announced at the same time as Marconi’s own-design Apollo marine main receiver (see WW 1971 December, page 609). And the Marconi H2310 Argo and H2311 were EC958 variants.
The RC410/R (and the RC411/R with coverage extended to VLF) were listed under the Marconi name in the WW 1970 June survey of communications receivers. But their subsequent fate is I think depicted by this advertisement from WW 1971 July:
Its purely speculation, but I surmise that the Eddystone EC958 rather than the RC410/R was seen as the best contender in that part of the professional HF general coverage receiver market that was a distinct performance and price level below the lofty level inhabited by the sophisticated upconversion receivers from Racal, Redifon, Plessey, etc. The EC958 production run was quite long at about 15 years.
Incidentally, the GEC BRT402 was used at Quartz Hill for HF broadcast relay purposes, until superseded by the Marconi HR21; see:
http://www.zl6qh.com/000468.html. I vaguely recall that there was a step-change quality improvement in the BBC news rebroadcasts on the National programme, so that was probably the cause, although I did not know that at the time.
Cheers,