Receiver identification [GEC RC410]

[G3PIJpeter]

This receiver was found a while ago lurking in the corner of a scrap yard by a friend of mine - hence the poor quality of the attached picture. It has a nixi tube read-out and the controls do not suggest great sophistication. The modifications tab on the front is likely MOD. I am told by my friend that it is mine if I can fix it - but I need to know first of all what it is before taking on carriage etc. I don't do 1980s PLL!

Many thanks

Peter G3PIJ

[turretslug]

GEC RC410? An interesting piece of transitional history if so, but might take a good dose of patience if it's sick!

[Radio Wrangler]

RC410, positive ID

I used to have one of the prototypes, along with the full service manual.

It is switch tuned, the tuning control rotates a switch and every rev a geneva machanism increments the next switch up and so on. Pull out the kHz knob (large right one) for slower tuning, but you still need to keep grabbing the fine tune pot to clarify SSB.

Large warpy paper/phenolic PCBs

You've GOT to see the gearbox and switches!

Not a brilliant performer. Early bipolar front end with an oddball mixer that's poor with large signals. Makes the RA1217 look wonderful!

Servomotor tuned preselector on the front end.

David

[G3PIJpeter]

Many thanks gentlemen - I knew there would be the necessary knowledge out there somewhere. There is just one relevant hit on the Web for RC410 at https://www.worthpoint.com/worthoped...iver-270586219 However, I cannot find a copy of the manual or circuit, either for sale or for download. When conditions permit, I shall travel over to Wales and liberate the receiver from the shipping container in which it now resides. The gearbox and switches alone should prove interesting and, who knows, a little light tinkering in the dark might yield some signs of life.
Best wishes
Peter G3PIJ

[G3PIJpeter]

Originally Posted by G3PIJpeter

There is just one relevant hit on the Web for RC410 at https://www.worthpoint.com/worthoped...iver-270586219

The link http://www.carlobramantiradio.it/gec_marconi.htm given on the above page contains some interesting extra information, albeit with an Italian commentary. Sufficient to get the renovations going. - Peter

[Synchrodyne]

The GEC RC410/R was described in detail in an 11-page article “A New Approach to H.F Communication Receiver Design” in GEC Journal 1967 Vol. 14 No.3, 1967. This covered both the receiver circuitry and the synthesizer, with block schematics but no full schematics. There were also some additional references in this post:https://www.vintage-radio.net/forum/...2&postcount=11.


Cheers,

[Radio Wrangler]

There is one on the loose in the UK, with manual. I donated it to the G-QRP club for George Dobbs to auction off at the annual October Doo.

I'm trying to remember who got it. Graham Firth got the Marconi H2900 a few years earlier. For some reason I think it might be Dave Penney, but I'm not 100% certain.

It won't be quick, but try an advert in Sprat or asking on the G-QRP webpage.

David

[m0cemdave]

The manual runs to three volumes (Issue 1, variously dated 9/1968 and 3/1969) and gives servicing information down to component level. Rather a lot to scan and a couple of kilos in weight.

But I seem to have both an original and a photocopy so if you do collect the receiver and decide to have a go at getting it working, please let me know and I may be able to help.

The receiver I have here has a badly warped circuit board (some are SRBP instead of FR4, what were they thinking?) which has resulted in it being consigned to the "don't go there" or "rainy day in the distant future" shelf...

[G3PIJpeter]

Originally Posted by m0cemdave

The manual runs to three volumes ... so if you do collect the receiver and decide to have a go at getting it working, please let me know and I may be able to help.

Thank you - that's a very kind offer. I have (Google) translated the text from the Italian website above and it may be that the basic information and circuit diagrams there will be sufficient - although the servo (400 Hz?) may be another matter. If it turns out to be a wreck (bearing in mind its recent past in a scrap yard) then the 100 kHz IF and filter strip may find use with my Eddystone S750. We shall see . . . . It will be a while before I venture into Wales but I shall keep this thread updated as and when.
Peter

[Radio Wrangler]

The servo, I think, is a DC brushed motor with a rather nice little gearbox driving the variable capacitor.

David

[turretslug]

Originally Posted by m0cemdave

The receiver I have here has a badly warped circuit board (some are SRBP instead of FR4, what were they thinking?)

GEC's long-running predecessor, the BRT400, had a reputation for heat-soak induced problems- maybe they felt that there was a tradition to uphold?

Interesting to read the attachment that mentioned use as a marine receiver- my understanding was that valves lingered longer in this role as early transistor receivers struggled with strong nearby RF that was part-and-parcel of the marine environment. Presumably someone, somewhere had signed it off as suitable. Also the fact that it was used on the Queen Mary, which supposedly has at least one of the monstrous Eddystone 700 receivers still on board in its museum role.

[Radio Wrangler]

The post orifice and other officialdom had some serious specs as to just what could be used as a ship's main receiver. Filter shape factors and things like that. A lot of famous and expensive receivers did not pass muster.

If your ship did not have a radio room with enough pieces of gear which met the appropriate standards for your class of vessel, you were not allowed to put to sea and not insurable.

David

[m0cemdave]

Some info here:

http://www.americanradiohistory.com/...22rc410%20r%22

and this is how it all ended:
http://www.americanradiohistory.com/...22rc410%20r%22

This advert may also be of interest, from the RNARS "The Communicator" magazine, Spring 1968:

[Radio Wrangler]

That clearance advert makes it look like GEC after amalgamation with Marconi had not only pulled the plug on their own GEC receiver product line but had decided to dump all the stock.

Never mind, not many years later the Marconi arm dropped themselves in the deepest doo doo with the H2900 and Sosin's article in their house journal comparing it to the competition. THey had to go begging all the recipients of said journal for the return of their copies. Oh-Ho! what's going on here? we all wondered and promptly returned them all with only the smallest delay for photocopying....

David

[Synchrodyne]

Regarding the marine application of the GEC RC410/R in question, something to bear in mind is that passenger vessels usually carried a wide range of radio equipment beyond the required set of regulation and approved equipment. Passenger R/T services often account for a large part of this. In these applications, equipment other than the GPO-approved models was often found, examples being the Racal RA17 and the Marconi HR22.

The GEC Journal article on the RC410/R did not mention marine applications, so it is reasonable to infer that GEC had not designed it to meet the GPO and international requirements for main receivers.

A Wireless World 1968 December article (pp.448,9) on the sound and vision equipment installed on the then-new QE2 vessel noted that the ship-to-shore R/T service used the GEC-AEI Lincompex II system in conjunction with GEC RC410/R receivers. Perhaps the QM (and the QE) were updated with similar equipment at around the same time. The original QM radio room and equipment were described in WW 1936 May 29, p.526ff. Probably the R/T equipment had already received updates. For example, SSB/ISB came into use for passenger R/T services from 1949 onwards, and one may imagine that the “Queens" would have been kept current.

Unfortunately, neither that WW article, nor an earlier 1968 July brief item (p.204) on the QE2 equipment mentioned what make and model of regulation main W/T receiver was fitted. Timing-wise, the QE2 was probably a year or so ahead of the new crop of marine main receivers that were solid-sate and high stability, ready for the early 1970s advent of SSB as the official marine communications medium.


Cheers,

[Radio Wrangler]

I seem to remember an advert for the Redifon 408 which I think came out a few years before the RC410 saying that it was used in one of the famous liners... QEII?

There were other cock-ups with marine receivers. Something happened that caused almost every RCA AR8516L to get dumped on the market all at once.

David

[G8BBZ]

Hi All,
I seem to remember that the statutory radio fit on the QE2 was Marconi, so it is very likely that the Redifon R408 was provided as the receiver as MIMCo were using the Redifon receiver widely at that time (along with some other marine radio suppliers like Hagenuk)
The R408 was ahead of it's time in being SSB ready, switch selection of USB and LSB being provided along with the "sliding doors" IF filter.

[John KC0G]

Re. post #15, the Queen Mary was withdrawn from Cunard service in late 1967, and the Queen Elizabeth in late 1968. It was known that they would both be replaced by the QE2. And so I wonder just how up to date they were kept.

[Synchrodyne]

The attachment to post #8 indicates that the receiver to which it referred was made in 1968, and that it came from the Queen Mary. A logical impossibility, I think, given that QM was decommissioned in 1967, before the receiver was built. Maybe someone got their Queens mixed up.

Re the SSB-ready Redifon R408, was it subsequently requalified against the GPO marine specifications, TSC102 for HF and TSC105 for MF? Marconi made the observation that the selectivity specifications in TSC102 and TSC105 were markedly different from those to be found in CCIR recommendations, which I think had previously been the industry benchmark. I understand that the marine SSB stability requirements were quite tough, as well. Still, by the time that marine SSB arrived, Redifon had released its R551 high-stability marine HF receiver, derived from the R550 and using the R499 core, so perhaps the suitability or not of the R408 was a moot point.

In the QE2 case, as GEC-AEI was supplying the Lincompex equipment, it probably preferred also to use a suitable receiver from its own GEC stable. But in 1968, there might not yet have been too many general purpose HF receivers available with the requisite stability.

When GEC absorbed EE (including Marconi) in 1969, and the GEC-AEI HF activities went into Marconi, the RC410/R was probably doomed. Its starting list price, £1150, was close to that of the Eddystone EC958, at £1137, so they were more-or-less direct competitors. The latter was more versatile, with coverage down to 10 kHz in standard form, and had more variants, including a qualified marine main receiver version (EC958/5, aka Marconi Nebula). It was also the basis for the Marconi Argus H2310 high-stability receiver, which probably helped to lock-in its future. Whether the EC958 was mechanically less complex than the RC410/R, I don’t know, but I don’t think it had any servomotors.


Cheers,

[Radio Wrangler]

Originally Posted by Synchrodyne

Whether the EC958 was mechanically less complex than the RC410/R, I don’t know, but I don’t think it had any servomotors.

You really have to have a look in an RC410 at all the gears and geneva wheels linking the tuning switches for that synth. It's a major feat of mechanical complexity and must have been almightily expensive to produce.

The next generation had TTL up/down counters setting data for synthesisers with a pulse generator on the tuning knob. THIS set did it all mechanically.

David