Henry's East Ealing Site
Updated: 10 May 2004 -- 30S-1 page added
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A Note on Emblems
One of the above four emblems would appear on S-Line equipment. The first was the winged emblem, which was superseded by the small round (meatball) emblem. Later, when Collins had been taken over by Rockwell, the Rockwell-Collins emblem appeared, but it is relatively scarce. The large round emblem, to the best of my knowledge, appeared only on the later versions of the 51S-1 receiver.
The Second Crystal Board
All S-Line radios tune a segment of 200KHz for each position of the band switch, thus to cover the whole range of 3.4-30MHz 145 crystals would be needed. The standard crystal board had room for 14 crystals, so that 14 200KHz segments could be available at any one time. Each version of the 75S, 32S and KWM radios were available as a version with an extra crystal board giving room for 14 more crystals. Mostly these were built as standard but conversion kits were available too. The second bank of crystals were activated by means of a small additional switch on the front panel, which also caused an second white frequency band panel too appear. None of the above applied to the 50S-1 receiver which tunes 1MHz segments.
For radio amateurs, the radios usually were delivered with crystals covering the marked frequency ranges on the front panel.
One thing I find delightful is to insert WARC band crystals into a radio that has never worked on these bands before, and to hear it spring to life on the new frequencies. It is to the credit of the designers that this was possible, mainly due to the ganged inductive tuning system.
Tuning was performed by a permeability tuned local oscillator (PTO), type 70K-2. In the S-Line this covered the range 2.5-2.7 MHz. There were two mixers in the signal path, using the PTO and a switched crystal oscillator as the local inputs. . Without getting into too much detail, there were in all designs a ganged series of narrow-band amplifying stages, tuned by variable inductors, as opposed to the more common ganged capacitors of the time. The careful design resulted in the achievement of a more or less constant performance over the whole frequency range. It has been my experience, that with a properly set up radio, additional crystals made new bands available without any additional "tweaking". How well thought out it was - and still is!