In respect of the Marconi H2900, as well as the previously mentioned Point-to-Point 1970 January article, there is another, also by B.M. Sosin, in “The Radio & Electronic Engineer”, 1971 July.
This covered much of the same ground, but did go into more detail on some aspects, such as the choice of the triple conversion scheme and its associated intermediate frequencies.
It also included a signal level map through the receiver, showing minimal gain and AGC action until the 3rd IF strip:
In comparison, here is the map for the HR92/HR93, Marconi’s top-of-the-line point-to-point SSB/ISB receiver (valve) of 1952. The HR92 was the double-diversity version, occupying two 7 ft high racks.
There was also a discussion of reciprocal mixing, including this chart:
That looked somewhat familiar; I had previously seen the similar chart that Racal had used in its 1974 articles on the RA1772 (*):
Racal went one down on Marconi, as it were, including a 100 dB line (representative of the RA1772) as well as the 70 and 90 dB lines used by Marconi.
Cheers,
(*) The two articles, both by R.F.E. Winn (apposite initials), were:
“Operational Aspects of HF Receiver Design”; Electronics & Power 1974 June 13.
“Synthesized Communications Receiver”; Wireless World 1974 October.