A Hams s Guide to RFI Ferrites Baluns and Audio Interfacing

A Hams s Guide to RFI Ferrites Baluns and Audio Interfacing

To solve interference problems, we must understand them. So we'll begin by describing the ways that RF interference is coupled into equipment and detected. There are several principal mechanisms at work. You should study this tutorial thoroughly to understand how these things work.
Antenna Action

Antenna Action

The most fundamental cause of radio interference to other systems is the fact that the wiring for those systems, both inside and outside the box, are antennas.
Common Mode and Differential Mode Signals

Common Mode and Differential Mode Signals

A differential mode signal is one that exists between the conductors of a cable. At any given point along the cable, current flowing on one conductor is precisely balanced by current flowing in the other direction on the other conductor.
Detection at Semiconductor Junctions

Detection at Semiconductor Junctions

Every semiconductor junction, whether part of a diode,transistor, or integrated circuit, is quite nonlinear, especially in the voltage region where it is beginningto conduct. In analog circuits, we prevent this non-linearity from causing distortion by properly biasing the circuitry, by using lots of negative feedback, and by preventing the signal from being large enough to cross into the cutoff region.
Insufficient Input and Output Filtering

Insufficient Input and Output Filtering

As hams, we know that equipment needs good input and output filtering to prevent RF from coming in on input and output wiring. Beginning in the 1950's, hams operating the HF bands were deluged with TVI complaints because television manufacturers failed to include high pass filters in their sets.
 
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