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Radio-Frequency Amplification From the Ground Up
397
PHONES OR LOUD SPEAKER ~
FIG. 6
In this five-tube circuit there are two stages of radio, a detector and two stages of audio-frequency amplification. A variocoupler and twin variometer, regenerative tuner is employed and the antenna circuit is tuned by a tapped coil and variable condenser. Long distance and loud signals are the reward for mastering the complex manipulation this outfit
requires
These circuits are more difficult to operate than the single-stage, transformer-coupled variety we have considered, but there are many experimenters who will derive a great deal of pleasure from the two-stage arrangement. Some fellows revel in complexities — and more power to them!
Before signing off, we must point to the two stages of audio-frequency, illustrated in Fig. 6. They follow immediately after the. detector assembly and no trouble should be experienced with applying them to any of the foregoing circuits. If you want to do yourself a favor, don't attempt too much at once, or, like the fellow who bites off too much, you won't be able to chew.
The following symbols are used in the figures and the capacities and values of in
ductances are those used in operating below 600 meters. Very few of them perform very well at 200 meters. Most radio-frequency transformers are designed to function at greatest efficiency on the broadcasting waves of 360 and 400. Some very ambitious claims that do not hold 'water are made by certain of the manufacturers and it is well for you to procure your radio-frequency transformers from .dealers who know and can be relied upon telling the truth concerning their wavelength range.
X, X1, X2, X3, X\ X5 indicate the standard multi-layer or spider-web coil mountings.
Ri and R2 are receiving filament rheostats.
R3 and R4 are 2oo-ohm potentiometers.
RFT indicates the R. F. transformer.
GC and R are the grid condenser and leak resistance; .005 is a .005 mfd. condenser.
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