The building and maintenance of amateur or "ham" radio equipment requires specialized skills. Ham operators, also called "hams," are licensed to do this work, which includes using a signal generator to adjust receiving and transmitting circuits. The signal generator provides a calibrated radio signal that allows the ham to tune the radio for frequency accuracy and best reception, or output signal. The ham needs to know how to connect the signal generator, adjust it to the proper test frequencies and modulation if required, and adjust the signal level.

A Standard Signal Source

Radio frequency signal generators are most commonly used by hams, since they generate signals in the amateur radio bands and allow modulation of the signal to simulate a standard radio transmission. Some use crystal-based frequency standards, but most provide a tuning capability by either a mechanical dial, digital adjustment or computer control. Even simple, home-built signal generators can be used to test basic receiver functions. Some hams may also have access at work to laboratory-quality units costing thousands of dollars.

Setup and Accessorizing

Signal generators can be set to produce a level of 1 uV (microvolt) or 50 uV to simulate "S1" and "S9" (top and lowest meter marks) signal strength. Adding an attenuator device in line allows the same settings for signal generators without accurate level settings. Some signal generators have settings for sample tones to be added to the RF signal, and most allow addition of an external audio signal, including one from an audio signal generator.


Tuning for Confidence

Using a simple, unmodulated signal, a ham can check the accuracy of each band of a radio receiver. It is important to ensure that ham equipment is accurate to avoid citations for transmitting outside the allocated ham frequency bands. The signal generator is connected to the antenna input of the receiver. When working on the radio, both modulated and unmodulated signals are used for adjusting intermediate frequency circuits used to convert RF to audio.

Tweaking and Adjusting

Special tools allow the adjustment of coils and capacitors within the radio by providing a nonmetallic means for turning slotted adjustment screws on capacitors and fitting a hexagonal space for moving a ferrite "slug" through a coil wound on a form. Small variable resistors, or potentiometers, may also be adjusted using these small tools. Without a signal generator providing an accurate reference signal, adjusting the circuits of the radio using these tools tends to be guesswork.

Clever Signal Generator Uses

Hams are known for innovation. Some have developed techniques for tuning and adjusting antenna equipment using radio principles that hams must learn to pass license tests. Combined with an oscilloscope and other equipment, hams can see the effect on signal generator output as they test and adjust antennas and "tuned circuits." For many hams, developing and applying new and clever techniques for equipment design and antenna development is part of the hobby.

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