In the circuit of Fig D the large condenser C say jufd is

Filled through the comparatively low resistance R (a few hundred or thousand ohms). It will then suddenly discharge through the strobo-tron to produce a brilliant but very brief flash of light provided the voltages on the grids are such as to permit the arc to strike in the tube. A pulse oscillator, whose frequency can be altered, is connected to the inner grid and serves to control the rate at which the flashes occur. In one commercial form of the apparatus, called a Strobotac, the flashing...

Audiofrequency Amplifiers

25.1 Introduction to Resistance-Capacitance Coupled Amplifiers. The principle of operation of the resistance-capacitance coupled amplifier was discussed in Sec. 13.5. These amplifiers are characterized 1. by being relatively inexpensive, 2. by good fidelity over comparatively wide frequency ranges, 3. by freedom from picking up undesired currents from the a.c. heater leads (since there are no coils to pick them up). 4. They are especially suited to pentode and high-mu triodes. 25.2. A Typical...

Microwaves

Radio waves whose length is less than approximately 1 meter are variously designated as microwaves, quasi-optical waves, centimeter or decimeter waves, and hyper-frequency waves. In the preceding chapter, a few oscillators were described which can produce these waves. In this chapter, additional methods of generating microwaves will be described, together with a brief treatment of their peculiarities. 38.2 Positive-Grid Oscillators. A type of oscillator was discovered in 1920...

Cxq

A plate-neutralized r.f. amplifier circuit Fig. 27 G. A grid-neutralized r.f. amplifier circuit In the grid-neutralized, circuit of Fig. 27 G, the rise and fall of the plate potential is transferred by the neutralizing condenser Cn through the grid coil, to counteract the voltage changes transferred by direct capacitive coupling inside the tube from plate to grid. In general, grid neutralization is less satisfactory than plate neutralization. Fig. 27 H. Inductive neutralization of a...

Direction Finders

Consider a loop of wire placed in the path of a vertically polarized1 radio wave. If its plane is set at right angles to the wave, equal voltages are induced in the two vertical arms, none in the horizontal wires. But the two voltages are in opposite directions, so that current cannot flow into an attached receiver, even if it is tuned to the transmitter and there will be no output of sound, or any reading on an output electrical meter. On the other hand, if the plane of the...

Uhf Transmitters And Receivers

Now we are to consider the transmitters and receivers for use at frequencies higher than 30 megacycles, corresponding to wave-lengths shorter than 10 meters. The division at 30 Mc. is entirely arbitrary and must not be considered as a sharp boundary line. The circuits used at the lower communications frequencies and at the ultra-high frequencies are very much the same, but the constructional features change progressively as the frequency becomes higher and higher. For...

Info

Effect of background voltages when in-phase left with the loop voltages, and at 90 quadrature, on the right spurious and loop voltages are in quadrature 90 right figure of Fig. 34 I , the minimae will be opposite each other but will not be sharp. Then, the correct line of propagation will be obtained, but the accuracy-will be greatly reduced because the minimae are not sharp. The in-phase errors are corrected by balancing the loop with, say, condensers, and by using an electrostatic...

Nt

Circuit diagram of an u h.f. transmitter Fig. 37 E. Circuit diagram of an u h.f. transmitter beam-power second-doubler amplifier and irom there to the neutralized push-pull amplifier using an 815 double-beam-power tube. At the ultra-high frequencies, the tuning condensers are small both electrically, 10 to 100 fifii. and physically, but the coils, while small electrically, are comparatively large in physical dimensions, the more so the higher the frequency. Around 100 Mc., for...

Magnetostriction Oscillator

A quartz crystal oscillator circuit the cathode of the tube. When the grid voltage changes, the electrostatic field across the crystal changes. Due to an inherent property of the crystal, known as the piezo-electric effect, small charges of electricity then appear on the surface of the crystal, accompanied by real but very small changes in the dimensions of the crystal. The small potentials so created act back upon the grid of the tube. When the frequency of oscillations of the...

Frequency Modulation

First re-read Sec. 16.2. The amplitude of the carrier wave remains constant in the frequency-modulation scheme. The frequency is varied from the mean or carrier value by an amount called the deviation frequency. If the deviation frequency is directly proportional to the amplitude of the audio signal, the transmitter is operating properly or linearly. 33.2 A Reactance Modulator. A reactance modulator changes the frequency of the tank circuit of the oscillator by changing its...

Further Discussion Of Oscillators

One of the outstanding problems in the design of vacuum-tube oscillators is that of keeping the frequency constant despite mechanical vibrations, temperature changes, voltage variations in the supply lines, and changes in the amount of power taken out of the circuit by the load. The effects of variable loading are greatly reduced by the use of electron coupling. Let us imagine that in the Hartley circuit of Fig. 14 B the actual metal plate is replaced by a...

T

Low-pass types use series inductance top figure . High-pass use series capacitance. Band-pass use series LC circuits. Band-elimination use parallel LC circuits bottom figure Of the host of possible lc combinations, a few simplified forms have been developed under the following assumptions and simplifications 1. The resistances of all parts of the filter circuits are to be kept as low as possible. We shall assume that the resistances are zero. Such filters are called...

Ultraudion Oscillator

The Evaporation Theory. The Change of Thermionic Current with Temperature of the Filament. Different Kinds of Filaments. Types of Cathodes. Saturation Currents. Space Charges. Plate Control of the Space Charge. Feld Emission. Secondary Emission. 11. Some Diode Rectifiers 65 Rectification. Half-Wave Rectifiers. Full-Wave Center-Tap Rectifiers. The Full-Wave Bridge Rectifier. Voltage for Rectifier Circuits. Component Parts of Rectifier Filters. Voltage Regulation. Vibrator Units....