[Radioroslyn]

Right after the war Collins developed a platform using a very stable tuneable oscillator called a permeability tuned oscillator, pto (typically around 1.5 to 4.0mc) that would tune a 1mc segment. The output of this osc was mixed w/a crystal osc. When used as the local oscilltor signal it was hard to beat.The output is very stable like +/- 10hz from a cold start. The drawback is that each band was limited to 1mc tuning range of the pto. This was the industry standard from the late 40's thru the 70's in high end sw receivers and later in ssb transceivers. When ssb gained popularity in the 50's and 60's stability became very important drift of a couple 100 cys change the tonal qualities of the voice heard so you would have to retune the station every minute or so.
Receivers like the Collins 75A1, 51J series and R390/390A where icons of their time.