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FRONT VIEW OF THE COMPLETED SET This outfit can be built for less than $50, uses a 201 -A and UV-igq tube, is surprisingly efficient in operation and easy to build
A Knock-Out Two-Tube Set
Combining the Advantages of Tuned Radio-Frequency Amplification, Audio-Frequency Amplification, the Neutrodyne Principle, Regeneration, and Reflexing and Loud Speaker Operation — All Without Radiation
By WALTER VAN B. ROBERTS
The set described costs less than $50 for parts, including tubes and batteries; is fairly easy to make, and as Mr. Roberts says, will equal the performance of far more elaborate and expensive sets. This set is another of the series built under the direction of RADIO BROADCAST, the first of which was the "Knock-Out One-Tube Reflex," described in our November, 1923, number which we are printing on page 496 of this issue.
If the reader has the parts and has built the one-tube set described last November, it will cost him about $10 more for the additional parts necessary for this set.
We are rushing the information on this set to our readers, and that explains why we do not show a panel lay-out. Next month, we will publish a complete "howto-make-it" article on this new receiver. — THE EDITOR.
THE circuit to be described is only one of many possible applications of the method which is used to obtain radio-frequency amplification without any tendency toward regeneration. This method is closely related to the ordinary neutrodyning system, but has the advantage that the coupling between primary and secondary of the radio-frequency transformer may be varied, thus allowing the maximum possible amplification over a large range of wavelengths.
The method employed by the writer for overcoming oscillation in the radio-frequency amplifier consists in winding the primary with a pair of wires, thus forming two separate windings coupled as tightly together as is physically possible. One of these windings is used as the* primary in the ordinary fashion. The other one is used only to prevent regeneration. Fig. i shows the arrangement schematically. S is the secondary, P the primary, and N the neutralizing winding. The capacity C should be exactly equal to the capacity between the grid