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Old 7th Apr 2019, 12:20 am   #61
Synchrodyne
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Default ISB Receivers

This is a continuation of an earlier, now closed thread with the same title, https://www.vintage-radio.net/forum/....php?t=103464&. It also refers to the current thread on the Plessey PR153A, at: https://www.vintage-radio.net/forum/...d.php?t=155440.

Recently I found an interesting article on point-to-point receivers of the first half of the 1950s, namely “New Developments in H.F. Receivers” by F.W.J. Sainsbury of Marconi. It is in the 1954 June issue of the journal “Electronic Engineering”. The whole issue was devoted to HF communications, and is available here: https://www.americanradiohistory.com...aster_Page.htm. I have extracted and attached the above-mentioned article.

EE 195406 HF Receivers.pdf

The article refers to the Marconi range of point-to-point receivers of the time, but I think that it is also generally illustrative. Marconi had what was basically a three-tiered range of receivers in order to meet the wide spread of performance vs. cost requirements of HF links. The top model, the HR93, had full ISB capability, as did the middle model, the HR21. On the other hand, the bottom model, the HR22, was SSB, with either/or sideband selection. I have the impression that the HR21 (and its HR23 triple-diversity and HR24 double-diversity derivatives) may have been the most used of that range of receivers. One may imagine a point-to-point receiving station having a small number of the HR92 type working on full-time fixed frequency links backed up by a larger number of the HR21 type, for which frequency changing was easier, working on various tasks.

Incidentally, that also gives a clear picture as to the purpose for which the HR22 was developed. That was unclear in the earlier discussion of this model in this thread: https://www.vintage-radio.net/forum/...d.php?t=101833. It is interesting that for the lowest tier telegraph receiver, Marconi used a standard communications receiver-plus-adaptor approach, whereas for the SSB case, it chose a single-box purpose-built receiver.

Also noted in the earlier thread was the apparent early adoption by the marine industry of SSB for passenger vessel telephone links. This is confirmed by an item in Electronics Engineering 1954 June:

Click image for larger version

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The UK GPO developed its own point-to-point ISB receiver, which was described in The Post Office Electrical Engineers’ Journal (POEEJ) for 1953 April. This issue is available here: http://www.coxhill.com/trlhistory/me...ril%201953.pdf. I have extracted the article:

POEEJ V46 Pt1 195304 SSB Receiver.pdf

That GPO receiver looks to have been comparable to the Marconi HR93. The 1952 October issue of the POEEJ, available at the same site, had a good general discussion of SSB in the point-to-point context. The Mullard GFR552 ISB receiver may have bene the commercial version of the GPO design:

POEEJ V46 Pt2 195307 rp.x Mullard GFR552.pdf

The tiered or hierarchical approach to point-to-point HF receiver design continued into the solid-state era, as evidenced by this table from a 1970 Marconi survey:

Point-to-Point 197008 p.115 Marconi Survey.pdf

The list included the Eddystone EC958. I suspect that it predated the release of the Marconi Apollo marine main receiver, which otherwise one might have expected to have been included in that list. The Apollo (sold by MWT as the N2050 as far as I know) used simple synthesis to provide high stability and bandspread on the HF marine bands only, and represented another vector in the highly varied range of approaches found in the early solid-state transitional period. The Marconi H2310 Argo was an even higher stability version of the EC958, although I have not seen any details as to how that was achieved.


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Old 7th Apr 2019, 2:28 am   #62
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Default Re: ISB Receivers

The amazing thing is how few of these receivers made it onto the surplus market, mainly due to deployment through leasing arrangements.

AR88s CR100s, RA17, RA1772, RA1792 there are a-plenty, but these commercial marine sets are almost unknown.

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Old 8th Apr 2019, 1:50 am   #63
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Default Re: ISB Receivers

Post #61 is a wonderful. Thank you.

I was not familiar with the June 1954 issue of Electronic Engineering. The whole issue is interesting. Marconi (MWT) were very well represented.

The POIEEJ article is one of a series which I have briefly seen but do not have copies. W.J. (John) Bray was the lead author of the first part. He was also the lead author for:
W.J. Bray, H.G. Lillicrap, and W.R.H. Lowry, "The Design of Transmitter Drives and Receivers for Single-Sideband Systems", Jounal IEE, Vol 94, Part IIIA, 1947, pp 298-327. This was one of the supporting papers for the IEE Radiocommunication convention in 1947
It would be interesting to know how things developed from 1947 to 1952

The 1970 Marconi survey is taken from the article by Beard. See post #35. It implies that the H2900 was suitable for naval communications. I have no idea if that was a standard feature, or the bullet-proof front-end was an optiion. No wonder that the H2900 was so expensive.

There is a description of the Marconi H2310 Argo in a 1970 article by Gould. Again see post #35. Again, I don't have a copy.

73 John

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Old 8th Apr 2019, 6:46 am   #64
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Default Re: ISB Receivers

The bullet-proof front end of the H2900 was standard, there were no options in this area. The one I had was a prototype and fully loaded with full diversity and ISB, so there were two front ends and four final IFs all sharing one synthesiser.

The RF amplifiers were 2N4391 JFETs, run at quit high quiescent currents. I'd always seen the 2N4391, 2N4392, 2N4393 FETs as analogue switch devices. It was an enlightenment to see them used as amplifiers.

The front end started with a multipole preselector tuned by a mechanical variable capacitor operated by a servo motor and gearbox.... very low intermod.

The first LO was a bank of crystal oscillators at 1MHz intervals mixing signals up to 70 or 80 MHz (can't remember) where they met a helical filter a bit over 1MHz wide.

The second LO was the PLL, but it used the first LO selected crystal oscillator as a component frequency giving it an offset which corrected any error or drift in that crystal. This converted signals down to 2MHz where they met the main bank of crystal filters.

The crystal oscillators gave very good phase noise performance, and the PLL had to tune only 1MHz.

Its weak spot was the PLL. A horrible stack of boards all wire-wrapped together. All inaccessible without unwrapping all its wires. Lock time was very slow. There would be no point in trying to adapt it for a tuning knob. You set the thumb-wheel switches and waited for the lock light.

When I got one (Swapped for a Redifon HFA125) the switching transistors in the SMPS had been raided by someone building an HF PA, and, of course, the synthesiser was faulty.

One weird thing is this receiver has no rear panel connectors. They are all behind a removable section of front panel and there is a cable duct to the rear.

David
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Old 8th Apr 2019, 7:41 pm   #65
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Default Re: ISB Receivers

I love the picture in the 1954 article - just what is the DF Receiver model, somewhere between a CR100 and Mercury 1017? (I want one!)
The Communal Aerial System mentioned there is the Pantenna which came in 3 different models, for AM, VHF-FM, or VHF TV+FM
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Old 8th Apr 2019, 11:40 pm   #66
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Default Re: ISB Receivers

John, I have since obtained some of the articles that you kindly listed in post #35. The National Library of Australia turned out to be a good source for this kind of material (https://copiesdirect.nla.gov.au/home), and more economical than Linda Hall. The remainder of that list will be for future acquisition. (Had I known about Linda Hall back when I was living in Dallas, TX, I would surely have visited it – KC is an easy drive from North TX.)

I have also found some additional journal references:

The Marconi Single Sideband Receiver Type CRD150/20B-SSR2; C.P. Beanland; Marconi Review 1949 January-February.

This setup, three HF receivers for diversity reception with “add-on” SSB/ISB adaptors, evidently preceded Marconi’s dedicated point-to-point receivers, starting with the HR92/93 and HR21 in 1952. The CRD150 looks to have been the diversity version of the CR150.

The Marconi Single-Sideband Receivers – Types HR92 and HR93; C.P. Beanland and F.I. Rockaby; Marconi Review 1952, pp.60-70

A new Approach to H.F. Receiver Design (GEC RC410/R); J.M. McAinsh & R.J. Bridge; GEC Journal Vol 34 No 3 1967


On-line, “Philco Single Sideband Communications 1957” is at: http://www.navy-radio.com/manuals/ssb-93224.pdf. This provides some information on American point-to-point receiver practice of the 1950s. (It is a very large .pdf, something like 150 Meg.)

The book “Single-sidebands in Communication Systems: A Bibliography” is available at: https://books.google.co.nz/books/abo...AJ&redir_esc=y.

This site: http://marconiincommunications.pbwor...Communications has a lot of information about Marconi equipment, with HF units at: http://marconiincommunications.pbwor...20-%20Products.

Related sites are: http://marconiinavionics.pbworks.com...%28Airborne%29, and http://marconiinmarine.pbworks.com/w...ded%20products.


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Old 9th Apr 2019, 7:42 am   #67
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Default Re: ISB Receivers

The GEC RC410 is another interesting receiver I once had.

It has switch tuning, but the switches are interconnected by a monster gearbox with Geneva-wheel mechanisms. rotate the main tuning knob by 10 steps and the next switch is incremented one step.... and so on up the chain. Big rollovers are stiff!

It has a motor driven preselector like the H2900, but its signal electronics are rather ordinary for the time lacking the high dynamic range and low phase noise efforts of the H2900. Was it one of the receivers Sosin panned? GEC-Marconi politics were not friendly, I recall hearing. I'm not sure of the timing of these sets versus when GEC owned Marconi.

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Old 9th Apr 2019, 9:41 am   #68
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GEC effectively acquired Marconi as part of its takeover of English Electric (EE) in 1968. GEC had also acquired AEI in 1967.

The RC410/R was released in 1967, as I understand it to replace the BRT400 series of HF receivers. So it was a “pure” GEC design.

Evidently the Marconi faction came to dominate the radio side of GEC’s business, and the RC410/R was redundant by 1971. However, I’d say that that was logical given the relativity of the legacy Marconi and GEC activities. More generally, which faction won out in the various parts of GEC seems to have varied by sector, and was not always logical. E.g. AEI was given the upper hand in traction, even though EE was an established integrated supplier in this field and had achieved sustained export success.

The RC410/R appears to have been the application of a synthesizer to an otherwise conventional HF receiver, tuning 2 to 30 MHz and with double conversion with 1.6 MHz and 100 kHz IFs. The synthesizer provided sufficient stability for SSB work. High dynamic range devices and techniques for using them might have been embryonic at the time. Thus the first mixer was “protected” in the traditional manner, with a four-gang, two-stage tuned RF amplifier. From the GEC Review article:

“The r.f. amplifier stages were initially designed using transistors, but at the higher frequencies in the tuning range difficulty was experienced in obtaining an overall noise figure of less than 12 dB without reducing the intermodulation selectivity to less than 40 dB below the signal response. Considerable improvements have been obtained by using field-effect transistors, resulting in an overall noise figure of not greater than 9 dB, together with an intermodulation selectivity of greater than 60 dB below the signal response for two unwanted signals at the aerial of 1.5 mV (e.m.f.) over the entire tuning range.”

Each RF amplifier stage used a cascode jfet, with agc bias applied to the lower unit source. The mixer and subsequent stages were bipolar.


But for example the Marconi Hydrus and Eddystone EC958 both used a basically similar approach, relying upon tightly tracking-tuned small-signal RF stages to protect the first mixer. The Hydrus used cascode jfets for all of the signal RF, mixer and IF stages through to the final demodulators. There was a single RF stage with bandpass tuned input. In this case agc bias was applied to the gate of the upper unit of the jfet cascode. The mixers had oscillator injection into the lower unit source.

The EC958 had a hybrid jfet/single-gate mosfet cascode RF amplifier with agc bias applied to the upper unit gate. It had a bandpass input above 1.6 MHz, single-tuned below that, although the marine version was bandpass down to 54 kHz. The three mixers were dual-gate mosfets. The IF strip was mostly jfets, with a BC107 or two. I’d guess that because it used a Wadley loop for high stability, it would have had lower phase noise than the RC410/R, though.

And the Marconi Apollo marine receiver followed established practice, with IFs of 1.1 MHz and 100 kHz. It had a dual-gate mosfet RF amplifier with bandpass tuned input and an MC1496 first mixer, bipolar thereafter. It used a simple synthesizer only for the bandspread marine HF bands where high stability was required.

My guess is that it was not so much that the GEC receiver was seen as “old technology”, as that Marconi saw no unique place in its comprehensive range (which included the Eddystone models) for the RC410/R that would justify its continued production. It had adopted EC958 variants as its H2310 Argo to cover the point-to-point slot below the Hydrus, and as its Nebula marine main receiver for the slot below the Apollo. And Eddystone had the forthcoming 1830 series to extend the solid-state range even further downwards, as well as an ISB version of the EC958.

The RC410/R was probably an unusual combination of tradition and modernity. But in the solid-state world it was also apparently rare in having two tuned RF stages in a four-gang front-end. That layout was of course legion with valve receivers, including most of the Marconi point-to-point models. But I cannot think of any other solid-state HF receivers that had that arrangement, whether with bipolar of fet devices. Rather the preference – in the relatively short time before high-level, high-dynamic range mixers preceded by wideband RF amplifiers took over - was to deploy two of the four gangs as a bandpass input, followed by a single RF amplifier stage and a single tuned interstage. The latter approach was not common in the valve era, although not unknown (e.g. the Eddystone 830 series).


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Old 9th Apr 2019, 2:49 pm   #69
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Default Re: ISB Receivers

Re. post #65, I am 430 miles north of Kansasa City, MO. Dallas, TX is about 500 miles south. The Linda Hall library is too far away just to drop into.

Louis Meulstree provides brief information on the army radio serts in his book "Wireless for the Warrior, Compendium 2" (Spark to Larkspur: Special Sets, Receivers and Larkspur). These sets are described as:

R211, triple diversity SSB receiver for the army wireless chain. Also known as the CRD/150/20A with 3 CRD/150/4 receivers, and a SSB rack type SSR2.

R217, also known as Marconi HR11. Adopted by the army for use in COMCAN. Shown as doing FSK, MCW and CW only.

R230, also known as Marconi HR27. Developed as a companion to the D11 transmitter.

R234, also known as Marconi HR28. Developed as a companion to the D11 and D13 transmitters.

R235, also known as Marconi HR23. Triple diversity receiver for COMCAN

In addition, under the discussion about the Station Radio E11, also known as the ST&C DS22, the radio was originally envisaged for use with the R217 for FSK (see above) or R228 (Marconi HR13) for SSB and ISB. The book suggests that the requirement for the R228 was abandoned and existing receivers used instead.

It is very good to see the Marconi information online. Receivers are listed at:
http://marconiincommunications.pbwor...20-%20Products

One army point-to-point receiver which was not made by Marconi was the R212. This was a triple diversity receiver built by ST&C in their "International" class. It was introduced in 1948/49.

Another indication of point-to-point practice in the USA in the 1950's is given in:
H.E. Goldstine, G.R. Hanselland R.E. Shock, "SSB Receiving and Transmitting Equipment for Point-to-Point Service on HF Radio Circuits", Proc. Institute Radio Engineers, Vol. 44 No. 12, Dec 1956, pp 1789-1794. It describes the SSB-R3 receiver and the SSB-T3 transmitter. This issue of the Proc. IRE was the "Single Sideband Issue"

The bibliography on Single-Sidebands is not widely known. It is also a very rare book - I have only found listings for copies in 5 or 6 libraries in the USA and Canada. If one is interested in SSB it is invaluable. It was published in the 1956, ie too late to be referenced in any of the papers in the Proc IRE Single Sideband issue (see above). This is the first volume which covers non-classified history. The second volume covered classified information. They were prepared by Mildred Benton, who was at one time the head librarian at the US Naval Research Laboratory. As it was prepared by a US Govt. employee in the course of their duties, it is not subject to copyright in the USA. This is why the full copy is available at Google.

73 John
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Old 10th Apr 2019, 9:02 pm   #70
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Default Re: ISB Receivers

Just for the record.
I believe that I am correct in saying that Civil Aviation in Australia never used ISB for point to point HF coms.
We used AM voice up until the 1960s, then SSB, until it was gradually replaced by satellite FM FDM.
The SSB networks were relatively extensive.

I also think Defence just used SSB, and at one time had considerable numbers of Collins HF80s.

I think OTC Australia used some ISB.
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Old 11th Apr 2019, 2:28 am   #71
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Default Re: ISB Receivers

As far as I know, ISB with pilot carrier (and SSB with pilot carrier) was used mostly on point-to-point links, with the change from AM happening in the years following WWII. Civil aviation HF went from AM to SSB supressed carrier. The merchant marine made the same change for HF in the 1970s.

The attached Wireless World article on Aircraft SSB included commentary as to why suppressed carrier operation was preferred in this case – Doppler effect was one of the reasons.

In hindsight perhaps this thread would have been better named as “Point-to-Point ISB and SSB Receivers”.


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Attached Files
File Type: pdf SSB Aircraft Communication WW 195810.pdf (1.41 MB, 13 views)

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Old 11th Apr 2019, 8:13 am   #72
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Default Re: ISB Receivers

I assume you've read "Single Sideband Circuits and Systems" By Pappenfuss, Schoenike, and Sabin etc?

It's a lot later book but gives the Collins view on SSB in the era when the KWM380 was a thing to aspire to. I found the speech processing sections rather interesting. I think there are two quite different editions.

Bill Sabin was a rather decent guy and was active on the internet from his local library long after retirement. There was a big argument with Walt Maxwell who propounded the view that transmitter output devices were matched (the transformed load Z had to be the complement of the valve/transistor anode/collector Zout) Bill on the other hand, knew better, but Maxwell was louder.

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Old 11th Apr 2019, 8:24 am   #73
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I have "Single Sideband Principles and Circuits" by Pappenfus, Bruene and Schoenike, the latter two of Collins, published by McGraw-Hill. There is no publication date, but the LCC # 63-13938 pegs it as 1963 or maybe 1964.

A very good reference book, and it does have a quite long chapter on signal processing.

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Old 11th Apr 2019, 8:38 am   #74
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Default Re: ISB Receivers

Australian Civil Aviation used SSB (USB supp carrier) for point to point (ATC centre to centre) from early 1960s to about 1984, supplemented by some HF RTTY. The SSB voice circuits had audio tone selcall to set up a voice call, so as not to waste ATC operator time.
It was rather elegantly engineered, and worked well.
Multiple frequencies for best time-of-day operation, (typically 2, 5, 8, 17, 23 MHz), feeding dedicated antennas, a lot of which were rhombics.
Some ATC centres had multiple groups of SSB circuits called NETs.


Australian Civil Aviation Air Ground Air used SSB, (again USB supp carrier) from 1982 onwards, for both domestic and international, and is still using it, although it is remoted from stations at optimised HF locations, rather than being installed at ATC centres.

Very interesting Thread; thanks to all.
I have also enjoyed reading the attachments very much.
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Old 21st Apr 2019, 5:29 am   #75
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Quote:
Originally Posted by John KC0G View Post
It is very good to see the Marconi information online. Receivers are listed at:
[url]http://marconiincommunications.pbworks.com/w/page/69290381/Receivers%20-%20Products[/url
Certainly there were quite a few Marconi HF receivers back in the valve era, ranging from quite elaborate to relatively simple. Given that Marconi was essentially supplying to the commercial and industrial market, I imagine that many of the more specialized receivers were aimed a specific set of tasks for point-to-point (PTP) receiving stations.

The same Marconi staffer, namely F.W.J. Sainsbury (FWJS), who wrote the article on HF receivers in Electronic Engineering (EE), 1954 June, also wrote section 16 of the Radio and Television Engineer’s Reference Book (R&TVERB), “Commercial High Frequency Radio Links”. Essentially the same article appeared in the 1st (1954), 3rd (1960) and 4th (1963) editions. (Probably it was also in the 2nd edition (1956), but I do not have that.) Therein FWJS described, without naming them, what were clearly the HR91 telegraph and HR93 ISB/SSB receivers, although circuit schematics were not provided. Accordingly I have extracted (from the 3rd edition) the part of section 16 that deals with those receivers, attached.

R&TVERB III p.16-13 to 26.pdf

FWJS also contributed section 22 of R&TVERB, “Communications Receivers”, this also being essentially the same across the 1st, 3rd and 4th editions. In that case, for the “worked example”, in this case with a circuit schematic, he used what looks very like a CR150 variant, although which one I have not figured out. Again I have extracted the part (from the 3rd edition) that deals with this receiver.

R&TVERB III p.22-16 to 22.pdf

The original CR150 covered 2.0 to 60 MHz in 5 bands, and was double conversion with IFs of 1.6 MHz and 465 kHz. The CRD150 was the triple diversity version of this receiver. The CRD150/20 appears to have been a derivative, used in the CRD150/20B + SSR2 diversity SSB receiver – which makes it very relevant here - and the CRD150/20B + HSR1 diversity telegraph receiver. These two appear to have been Marconi’s top point-to-point offerings before the advent of the HR91 and HR92/93 in 1952. As best I can determine, the individual receivers in the CRD150/20B assembly were of the CR150/4 type. This covered 1.5 to 30 MHz in five bands, with IFs of 1.2 MHz and 465 kHz.

The CR150/3 was said to be a redesigned CR150, with the same coverage and same IFs, and with the provision for crystal control of the first oscillator. Possibly the CR150/4 incorporated the same changes but had different frequency coverage to suit the point-to-point requirements.

Later came the CR150/6, which used miniature valves and covered 2.0 to 32 MHz in four bands with IFs of 1.6 MHz and 465 kHz. It was in place by 1958, but how much earlier than that I don’t know.

The “unknown” CR150-series receiver described in R&TVERB used miniature valves, tuned 1.5 to 30 MHz in five bands, like the CR150/4, and had IFs of 1.2 MHz and 100 kHz. Possibly the choice of the 100 kHz second IF was to facilitate coupling to outboard processors that expected to see a 100 kHz input, probably the modal final IF in much such point-to-point station equipment of the period. But then one could wonder why the – presumably later – CR150/6 went back to 465 kHz.

The unknown receiver would likely have been in place ahead of the 1954 publication date of R&TVERB 1st, perhaps even in 1953. The HR22 Group 3 SSB receiver was in some ways a derivative of the CR150 series. It used miniature valves, covered 2.0 to 32 MHz in four bands and had IFs of 1.6 MHz and 100 kHz. It was in place by mid-1954, when the EE article was published, but probably not much before. Whereas the unknown receiver used many Osram “77-series” valves, as might be expected, the HR22 appears to have been based to some extent of the lesser-known Osram “727” series which had been announced around 1953-54, although they were simply renamed American standard valves.

Given that the CR150 series was a general-purpose receiver, with some sold on the surplus market, and not just a point-to-point specialty item, I imagine that someone, somewhere has amassed chapter, verse and minutiae on its chronology and variants, and the information is on the web somewhere – I just have not yet found it.

Quote:
Originally Posted by John KC0G View Post
Re. post #65, I am 430 miles north of Kansas City, MO. Dallas, TX is about 500 miles south. The Linda Hall library is too far away just to drop into.
Yes, hardly “drop-in” distance from Dallas. Had I known about it, it was the kind of trip I might have done towards the year-end to use up a couple or three vacation days that otherwise would be lost. The strange thing is, my neighbours and friends in Dallas still had a farmhouse in western Iowa – between the river and the Loess Hills – that they used as a vacation destination, and I visited there a few times, driving through KC, so Linda Hall would have been an easy stop-off.


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Old 21st Apr 2019, 8:11 am   #76
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Is KC one of those places where, if you wait long enough, everyone comes past? I sometimes visit an FCC certified lab a dozen of two miles to the south of the city and use a hotel in Overland Park. The whole area seems to be the centre of the universe as far as avionics is concerned.

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Old 21st Apr 2019, 12:56 pm   #77
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I suspect that the people at Rockwell-Collins, now called Collins Aerospace, in Cedar Rapids, Iowa might have something to say about that. Having said that it is only just over 300 miles from KC - not far in US terms.

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Old 23rd Apr 2019, 2:22 am   #78
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Default Re: ISB Receivers

I have found a little more on the Marconi CR150 series receivers.

The CR150-2 had frequency coverage of 1.5 to 22 MHz in 4 bands. It was mentioned a Practical Wireless 1967 October article on the CR100 and CR150, p.414ff. I’d guess that this variant would have introduced the 1.2 MHz 1st IF, as1.6 MHz would not have worked so well for a receiver that tuned down to 1.6 MHz. In the case of the CR150, the 1.6 MHz 1st IF was 80% of the lowest received frequency, namely 2.0 MHz. It would that the same proportion was retained for the CR150/2, 1.2 MHz being 80% of 1.5 MHz.

The CR150/5 was mentioned in connection with an enhanced radio equipment fitout for the vessel SS Gothic in anticipation of its use for a Royal Tour, see: http://maritimeradio.org/ship-statio...or-royal-tour/, which includes an excerpt from the Marconi Mariner 1952 January-February. Noted was that a CR150/3 was installed for traffic purposes, with a CR150/5 used for cuing in respect of BBC commentaries. Thus we can deduce that the CR150/5 was available by the beginning of 1952, but that the CR150/6 (successor to the CR150/3) might not have been, hence the use of the CR150/3. Why two different CR150 variants were used is unknown. Different frequency coverage requirements was a possibility. The CR150/5 is at least a suspect for being the “unknown” variant described in R&TVERB. Essentially the same information about the Gothic installation was provided in an article in PW 1954 January, p.24ff. Interesting was that the installation was a joint effort between MIMCO and MW&T.

Judging by this item - http://www.nas.gov.sg/archivesonline...b-001a4a5ba61b - the CR150/6 was in place by the beginning of 1954, though, and it was associated with the HU12 double diversity telegraph receiving unit. This was the Group 3 telegraph equipment mentioned in the EE 1954 June article, intended for use with regular communications receivers. It seems reasonable that the CR150/6 would have been Marconi’s default receiver offering for this purpose.

During the valve era, the range of receivers within Marconi’s Group 3 point-to-point category appears to have been progressively extended. The HR100 was a rebadged Eddystone 750. The HR110 was an Eddystone 910 variant. And the H2301 was an Eddystone 880 variant with a choice of 3 or 6 kHz SSB filters and a crystal-controlled carrier insertion oscillator. The HR120 was an own-design high-stability receiver of the “converter” type with a crystal-controlled first oscillator, decade switch tuned. One imagines that it was intended to offer frequency-agile SSB capability with better than VFO stability and perhaps approaching that provided by the spot frequency crystal option in the HR22. It does not appear to have been fitted for pilot carrier recovery, though. The HR120 appeared in 1960. That was after Racal had introduced outboard SSB/ISB adaptors (and telegraph adaptors) to work with its RA17 HF receiver, taking advantage of the good stability of the latter at all frequencies.


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Old 23rd Apr 2019, 2:33 am   #79
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Default Re: ISB Receivers

An example of early 1950s American practice in respect of high-performance point-to-point SSB/ISB receivers is provided by the Crosby 155 triple-diversity unit, described in the attached article from Communication Engineering 1953 July-August.

Crosby SSB Diversity Units CE (FM-TV) 195307,08.pdf

It comprised a trio of Crosby SSB adaptors and a Crosby diversity combing unit attached to a trio of Hammarlund SP600JX HF receivers. So in using the HF receiver + adaptor combination, it was broadly similar to the Marconi CRD150/20B + SSR2 setup.

Perhaps unusually for “full-sized” SSB/ISB units, it had electronic AFC via a reactance modulator rather than a motor-driven system. To ensure that the tuning did not revert to a nominal centre position when a received carrier dropped out, the AFC system included a so-called “infinite time constant” that held position when the carrier returned, thus imparting the same behaviour as obtained from motor-drive systems.

Essentially the same setup was available using Collins 51J receivers instead of the Hammarlund SP600JX. This was noted in an item in Tele-Tech 1953 March.

from Tele-Tech 195303 p.100.pdf

Another feature of the Crosby SSB unit was that it also provided for exalted carrier reception of AM (and PM) transmissions. By way of background, Crosby had worked for RCA for many years in both the FM and point-to-point communication fields. For the latter he had developed diversity receiving systems and also exalted carrier systems, the latter the subject of a paper in 1945, after he had left RCA, I think. He established his own company in 1948, which as well as developing systems, also manufactured diversity and exalted carrier adaptors, as well as exalted carrier receiving systems based upon proprietary HF receivers. From there it would have been but a short step to building ISB adaptors, once it was obvious where the future of HF communications lay. That SSB/ISB receivers could be – and were used for exalted carrier reception of AM transmissions essentially made dedicated exalted carrier receiving systems redundant. Crosby may have envisaged wider use of PM at HF, but that didn’t happen per se, although of course SSB is a mixture of AM and PM.

Here are a couple of 1951 Crosby advertisements for firstly, a triple-diversity exalted carrier receiver and secondly, a triple-diversity SSB receiver.


Electronics 195103 p.334 Crosby Exalted Carrier Receiver.pdf Electronics 195112 p.390 Crosby Triple Diversity SSB Diversity Receiver.pdf


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Old 24th Apr 2019, 4:31 am   #80
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Default Re: ISB Receivers

An unusual American SSB/ISB adaptor, for use with communications receivers, was the General Electric (GE) YRS-1 of 1948. This was apparently aimed at both the professional/commercial and amateur markets. It was described in several magazine articles of the time, of which two are attached.

GE YRS-1 Electronics 194807.pdf


GE YRS-1 WW 194807.pdf

It used a locked oscillator for local carrier regeneration, and the Norgaard phasing method (with Dome phase-shift networks) for sideband separation. The output could be switched to either sideband, locked oscillator DSB reception, or to “normal” reception using the AF output of the associated communications receiver. Nonetheless it is evident from the schematic that the separated sidebands were available simultaneously, so it could have been used for ISB reception.

Locked oscillator DSB reception was in fact exalted carrier reception, of which Crosby was a major exponent of the time. However, Crosby used reconditioned carrier rather than a locked oscillator. And although his patent (but not his 1945 paper) showed the possibility of sideband separation by the phasing method, it is not clear that it was actually used on any Crosby receivers. Press Wireless also made exalted carrier HF point-to-point receivers in the later 1940s, and these did use a locked oscillator for carrier regeneration, but as far as I know did not include sideband separation.

How well the GE YRS-1 worked, or how long it remained in production is unknown. But its technique turned out to be well away from what became the mainstream vector for professional SSB/ISB receivers, namely the use of IF filters for sideband separation and carrier extraction, along with AFC loops.

One could say that the YRS-1 presaged the PLL synchronous, selectable sideband AM demodulation technique that appeared (at various levels of execution competence) in amateur, domestic and semi-professional HF receivers during the 1980s. Professional point-to-point SSB/ISB receivers appear to have stayed with IF sideband separation and carrier extraction filters and AFC loops, although in some cases in the solid-state era, PLLs were used for carrier regeneration, an example being the Eddystone EC958/12.


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