Quote:
Originally Posted by Andrew Sinclair
The CR100 was introduced in about 1940, as the existing equipment could not be mass-produced. (There are surviving examples in the HMS Collingwood heritage collection, I don't think they would have had a high performance either.)
I have attached a page from "Low Medium and High Frequency Communication to and from HM Ships" by Anderson and Grainger (1947). This paper explains much of the thinking at the time.
|
Thanks for posting that, it made for an interesting read. Reading between the lines, peace-time military equipment can have a tendency to over-engineering without necessarily resulting in performance bonus. If only a relatively small number of examples of a piece of equipment are needed, both the cost and production effort won't raise too many eyebrows but once quantities required increase by orders of magnitude, price and urgency become very significant indeed.
It's hardly surprising that the Eddystone 358 came to be regarded as an oscillator radiation liability- the coil-pack-in-a-pluggable-metal-case recipe will cause circulating current coupling between sections without specific effort to isolate them electrically, it's noteworthy that the other receiver famous for adopting this format, the HRO, also had this reputation. The Scott Laboratories shipboard receivers took care to isolate front-end sections with insulating bushes and strips, plus the use of insulating switch-shafts and gang-capacitor couplings. Post-war, many manufacturers adopted these measures- one thing that marked the Eddystone 680's evolution into the 730 was the use of sectioned screening plates secured by insulating washers to minimise stray coupling.
The CR100's metalwork is simple to the point of looking almost home-made, but understandable under the circumstances. Part of the greatness of the AR88 is that it combines advanced techniques such as the stable, low-loss polystyrene coil formers, bandspreading by switching gang-capacitor sections and oscillator voltage regulation with simple steel foldings and pressings that were inexpensive yet precisely made. It certainly followed the US mass-production philosophy of investing to save, i.e. the machine that stamps precise parts out of standard mild steel sheet might cost lots of money but if it can repeat that process thousands of times with inexpensive feedstock, then it's worth it.