This work is licensed under a Creative Commons Attribution 3.0 Unported License.
This radio was donated to the Dundee Amateur Radio Club. It started life as a National HRO Senior, serial number M435. It has all four original coil sets, although only set D's serial number matches the radio itself (M435); set C is numbered something like "SO623A", set B came from N744, and set A has no number.
This set appears to date from 1941, after National started using letter-prefix serial numbers again for wartime production, but before the introduction of the HRO-M. It has: grey chassis, plastic S-meter with backlight, square IF cans, round spacers in the tuning capacitor, plug-in crystal, commercial (but early) resistors, National model tag on front, coil boxes with paper scales, and a patent license label on back dated 1/15/41. One oddity: the valve types stamped on the chassis are for the 2.5V version, but the sockets for V5/V6 have "6D6" printed on them (and, indeed, 6D6s were fitted).
A previous owner rebuilt the set using miniature valves, adding several features to make it more useful for amateur radio. (I traced out the modified circuit.) I plan to return it to approximately its original configuration.
If you'd like to know what this set is supposed to look like, have a look at W1UJR's HRO Senior restoration, or at WA7YBS's comprehensive page on the HRO and its history. More information on the HRO series can be found in articles by Charles Fisher and Barry Williams.
This work is licensed under a Creative Commons Attribution 3.0 Unported License.
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