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:
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.
Cheers,