Sparton 301 radio the "Equasonne'
Sparks-Withington Co. was a major player in home radios in the
1920s - the 1950s. The company also manufactured television sets
from the late '30s well into the late 1950s when it sold out to
Sparton radios were not you usual run of the mill sets, they were high quality in every respect. The late 20's models were unique in several ways, not wanting to be a slave to RCA, they had their own line of vacuum tubes that did not require the RCA license. Most significant was the unique tuning circuit as used in the above and other "Equasonne" models. It was well known in the late 1920's that the superheterodyne circuit was superior in every way than the common TRF circuit. Sparton Radios incorporated a much improved TRF circuit that was not subject to RCA patents or license. This circuit (which is basically a tuned filter) was used in many Sparton models starting in 1928. The unique tuner provided very precise and selective tuning which consisted of a 4 stages of un-amplified tuned RF. This was known as the "Technidyne" circuit, each stage was completely shielded from each other as well as all external influence. Then followed a six stage broadband cascade RF amplifier. An improved version of this tuner was used in a later model 737. The improved circuit was identical in every respect to the earlier version except an RF amplifier was added in front of the tuned filter.
For ore info on the Sparton Equasonne, visit: http://spartonequasonne.webs.com/