Graymark radio kit
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An even smaller variable cap of 3-30 pF is used as an antenna trimmer. The smaller 15 pF bandspread cap tunes a small portion of that range. The main "Band set" variable capacitor sets the approximate tuning range. Like most similar sets, the Ocean Hopper has four controls, three of which are variable capacitors. The same effect occurs at radio frequencies but just prior to that squeal, the regenerative circuit has tremendous amplification and narrow bandwidth. Too much regeneration is a bit like holding a public address microphone too close to its speaker, resulting in a squeal of positive feedback. That winding is traditionally called a "tickler" winding and feeds back a bit of the amplified tuned signal to the tube's grid. This Ocean Hopper's regeneration control is a variable resistor which variably shunts (shorts out) the RF energy on the feedback winding on the 12AT6 plate. The Ocean Hopper differs from the earliest circuits mainly in the choice of how regeneration is controlled. Regenerative circuits, discovered by Edwin Armstrong, date back to the very beginning of vacuum tube radios. The radio has screw connections for an external speaker, pin jacks for headphones, and a fahnestock clip for antenna connection. Tubes are 35W4 as rectifier, 50C5 for audio output and a 12AT6 triode as the regenerative RF detector. Five plug-in coils sold separately increase the coverage from 165 KHz to 35 MHz. This Knight Ocean Hopper receiver from Allied Radio is a three tube regenerative set covering the broadcast band. Knight Ocean Hopper regenerative receiver Knight Ocean Hopper receiver