The Radioman's Manual of RF Devices, Principles and Practices
Dealing with the RF aspects of radio communication, this is an indispensable book for anyone involved in land mobile radio, ham radio, marine radio or aviation radio.
TABLE OF CONTENTS The Radioman's Manual of RF Devices, Principles and Practices
3.4: Applications
3.4 Applications
There are a great many applications of the RF spectrum analyzer. The chief limitation of the usefulness of the spectrum analyzer is the imagination or lack of knowledge of the user. Some of the more common uses and techniques are presented here.
3.4.1 Transmitter testing
One of the most common uses of the spectrum analyzer is testing transmitters. Tuning a transmitter by adjusting to produce maximum power on a wattmeter is called blind tuning. It is a good idea to observe the transmitter signal on a spectrum analyzer while the transmitter is being tuned.
3.4.1.1 Spurious emissions
While doing some volunteer radio work for the local chapter of the American Red Cross, a funny thing happened. Upon connecting one of the radios to the test bench setup and keying the transmitter, the power meter indicated near normal power output. However, an examination of the spectrum display indicated trouble. The power appeared to be, mostly, in all the wrong places (see Figure 3 27).
Figure 3 27: The spectrum display of a transmitter output indicated a number of spurs spread out over a wide spectrum around the transmitter frequency. Notice that some of the spurious signals are at a higher level than the carrier.
After a careful retuning of the transmitter from oscillator to final output, the transmitter indicated proper power output and the spectrum display was now clean (see Figure 3 28). Without the spectrum analyzer, the radio might have been placed in service and caused interference...
Copyright Noble Publishing Corporation 2004 under license agreement with Books24x7
