From the Rolls-Royce experimental archive: a quarter of a million communications from Rolls-Royce, 1906 to 1960's. Documents from the Sir Henry Royce Memorial Foundation (SHRMF).
Car radio technology, including comparisons, aerials, housing, and power systems.
| Identifier | ExFiles\Box 178\2\ img026 | |
| Date | 13th April 1940 | |
| Rm{William Robotham - Chief Engineer} - 2. Serial No. 76. OY.1/D/Apr.13.40. 2) I was wrong in the information that I picked up from Mackworth Rees. The English sets are all super-heterodyne and have been so for some years. A modern super-heterodyne set squeals less than tuned radio frequency sets. The English sets differ principally from American in requiring two frequency bands which, incidentally, will not be on the Oldsmobile set which we shall send you. It is even more desirable in England than here to obtain high selectivity, but the British sets inspected by Delco did not show anything like precise selectivity. The breakdown which you mention in your letter is probably from moisture. Under the hot and cold conditions of car use, condensation is a major factor tending towards breakdown of the insulation. 3) With regard to aerials, the Zephyr practice of using an insulated trunk door is only good in metropolitan areas and is definitely louder when going away from the broadcasting station. Lincolns sold in this country fit whipsocket aerials ($2.50) to all customers in country districts. All aerials mounted low on the car have been abandoned because they are constantly being shielded by obstructions and by the mass of the car itself, and, therefore, do not give constant reception. The whipsocket type is undoubtedly the favourite and as now mounted is not unsightly and does not loosen up. Several new types of adjustment with bowden wires and reels are on the market. 4) One of the main recent improvements has been to make the radio box as a single unit, mounted behind a central grille in the instrument board designed for its reception. The size of the box is 9-1/2" square by 6" deep, and this contains everything. There are no straggling cables and the rear of the dashboard is left clear for mounting heater, etc. In 1942, by using an oval type speaker instead of the present 8" circular type, the size of this box will be reduced to 8" vertical by 9-1/2" wide by 6" deep. It is found that by mounting the speaker high in the car instead of low down on the dash, there is a saving of about 40% in the current required because of the increased audibility. Motor generator sets are no longer used on any car radios. They were heavy, expensive, and only about 40% efficient. The present vibrators have an efficiency of 65%. They are virtually | ||