Wave Transmitter

In the first chapter, a very primitive radio transmitter was described, and it was mentioned that it was similar to the one on the famous ship Titanic. The transmitter shown in Fig. 19.2 is closer to the Titanic s radio, because it has a capacitor in parallel with the inductor, making a tuned resonant tank circuit (see index if necessary). This concentrates the transmissions at one particular frequency range. Also, the oscillating relay repeats those transmissions automatically. If an antenna were connected, as on page 181, the radio waves could be heard on an AM radio farther away. 

As an additional exercise, the circuit of Fig. 19.2 might be built and listened to with a portable AM radio. A louder signal will be heard, compared to the experiment in Chapter 1, because of the capacitor storing energy that then gets discharged within about one millisecond. Also, the crystal radio in Fig. 19.1 should be able to pick up the signals. 

The radio wave is changed (modulated) according to the shape of the sound wave by changing its magnetic intensity (amplitude). Therefore this type of transmission is called amplitude modulation.  

The radio transmitter has modulated the RF, and the radio receiver demodulates it, which is also called detecting it. Some radios can do either of these, and they can be called transceivers. (They could also logically be called MODulator/DEModulatorS, or modems. However, that term is reserved for 

The original sound wave in the air (middle of page 207) had a sine wave shape (page 77). It started with zero pressure, then compression, then zero for an instant, then a slight vacuum. In the AM radio wave of Fig. 19.4, the upper arrow points to where zero air pressure occurred at the studio microphone, and the top of the radio wave shows when compression occurred. The middle of the radio wave corresponds to the vacuum half of the sound wave. 

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People are invisible to radio waves. In other words, there should be no effect when standing between a radio-wave transmitter and its receiver. Conversely, humans are not invisible to light in the wavelength range 100-1000 nm - we say they are opaque, which is most easily proved by asking a person to stand in the path of a light source such as a torch, and seeing the shadow cast. 

GAF Carbonyl Iron Powders. Trademark of General Aniline and Film Corp, 435 Hudson St, New York, 10014, for microscopic almost perfect spheres of very pure iron (99 6 99.9% Fe). They are produced in eleven carefully controlled grades ranging in particle size from 3 to 20 microns in diam. Used in high frequency cores for radio, telephone, television, short wave transmitters, radar receivers and direction finders. Also used... 

Use High-frequency cores for radio, telephone, television, short-wave transmitters, radar receivers, direction finders alloying agents catalysts powder metallurgy magnetic fluids. 

The sonic tool measures the time taken for a sound wave to pass through the formation. Sound waves travel in high density (i.e. low porosity) formation faster than in low density (high porosity) formation. The porosity can be determined by measuring the transit time for the sound wave to travel between a transmitter and receiver, provided the rock matrix and fluid are known. 

The use of Lamb waves offers the possibility of rapid long-range in-service inspection. Receiver and transmitter probes are positioned single sided - access is only required from one side of the specimen - in a pitch-catch-arrangement, the receiver being outside tbe field of the specular reflection. 

The term transmittance (T) at a given wave length is defined by... 

The frequency of microwave radiation lies between that of IR radiation and high frequency radio waves and the boundaries between these regions are not fixed [221]. The microwaves are generated in a transmitter (magnetron) which possesses a stalk which penetrates Uke a radio antenna into a hollow energy guide (Fig. 48). This leads the electromagnetic waves into the reaction chamber (power about... 

The two other foam sensors mentioned above are ultrasound and rotating disks. The ultrasound sensor is a transmitter and receiver mounted opposite to each other and operating at 25—40 kHz. In the bioreactor, the waves are absorbed by the foam and the signal is generated. The rotational disk foam sensor is a mechanical foam breaker which is used by increasing the rotational resistance. 

A with a max at 3800A. The absorption overlap of the nitrocompds is plainly evident. The position and slope of each curve in Fig 1 can be qualitatively correlated with the absorption range and % transmittance at the peak for each compd. Nitro me thane, which absorbs more at shorter wave lengths and exhibits the least overlap of the toluene-PPO emission spectrum, accordingly has the least effect on the count Tate of the pure scintiliator... 

Purifying the Benzene. Occasionally a drum of technical grade benzene is encountered, the contents of which will develop a pronounced pink color when subjected to the analytical procedure. A typical transmittance-wave-length curve from a 250-ml. specimen of such processed benzene is shown in Figure 4. By comparison with... 

Figure 4. Typical Transmittance-Wave-Length Curve for Processed Unknown Constituent of Technical Grade Benzene...

Figure 9. Transmittance-Wave-Length Curves for Dyed Parathion in 20% Ethyl Alcohol...

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