SITUATION
The reactance-tube modulator used in a short-range, military FM radio
transmitter is shown in figure 2-6. Coil L and capacitor C make up the frequency-
determining circuit of the Hartley oscillator that provides a center frequency of
22.6 MHz. The characteristics of the modulator tube are as follows:
transconductance (gm) = 5,000 micromhos.
ac plate resistance (rp) = 0.7 megohm.
Exercises 3 thru 5 are based on this situation.
Figure 2-6.
Reactance-tube modulator.
3. The electron-tube characteristics described in paragraph 21 of TM 11-668 are
computed under static conditions, that is, without a load resistance.
The
amplification factor of the electron tube used in the modulator circuit is
approximately
a. 2,500.
c.
5,000.
b. 3,500.
d.
7,100.
4. At the center frequency of the oscillator, the impedance across the plate
load consisting of R1 and C1 is
a. less than lOOK.
c.
between 125K and 150K.
b. between 100K and 125K.
d.
greater than 200K.
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