GILFILLAN MODEL R-550 REGENERATIVE RADIO, 1923

IDENTIFICATION

It appears that very little is known about radios made by Gilfillan Bros. prior to the production of their series of neutrodyne radios. Cataloging of radio parts made by them showed up in 1923¹ and they produced a two tube reflexed receiver in kit form, the Model RA-1, in 1924¹. However, Radio Collector=s Guide, by Morgan McMahon, shows a 1923 listing for two (2) radios, a Model R-475 which is listed as a crystal set, and, a Model R550 using three (3) tubes, a detector stage and two (2) amplifier stages. No three (3) tube radios are shown for 1924.

The above facts, plus the fact that all components except the phone jacks and audio transformers are marked with the Gilfillan Bros. trademark, is the basis for my identification of this radio as a Gilfillan Bros. Model R-550.

MANUFACTURING

This radio was very obviously made in limited quantities as the panel has all the layout scribing on the backside and most of the components are standard items shown in Gilfillan=s cataloging from 1923. The workmanship shown in the radio=s construction, and it=s components, is outstanding B the bending of the bus bar, which is hard-drawn round #16 copper, and, the molded pattern on the binding post nuts matches that on the front panel knobs. But on the other hand, the cabinet is very cheaply made and does not begin to match the normal quality of Gilfillan products B maybe the radio was sold without a cabinet?

CIRCUIT DESCRIPTION

This radio uses three (3) tubes in a regenerative RF detector & two stage audio amplifier configuration. Individual filament rheostats as well as audio output >phone jacks are provided for each stage of the radio, thereby allowing the operator complete control over the receiver. The signal from the antenna is fed to the primary of a variocoupler which is series tuned by a tap switch combined with a tuning condenser & vernier. The secondary of the variocoupler is fed through a variometer and coupling condenser to the detector grid. It is interesting to note that there never was a grid leak, therefore this radio was intended to use a UV200 detector tube. The +22-1/2 VDC detector plate voltage is fed through the audio output jack circuit to the plate variometer and on to the tube plate. Two conventional transformer (General Radio, apparently before Gilfillan was making their own) coupled audio amplifier stages follow the detector stage.