![]() ![]() In a mixer valve of any type, the non linearity varies with the voltage applied to one of its control elements or grids, or even its cathode as is the case in Figure 1. All valves have non linearity, and the amount of non linearity depends on how the tube or valve is biased on its grids and on its construction. The schematic for one such mixer is shown in Figure 1. In order to do this, a special non-linear radio valve called a mixer was developed. This fixed frequency is called the Intermediate Frequency, or simply the I.F. This type of receiver converts the incoming frequency from the receiver’s antenna to a fixed frequency, no matter what the incoming frequency is. To combat this problem, manufacturers of radio receivers needed to turn their attention to the Superheterodyne Technique. This helps avoid several overlapping broadcast stations being heard at the same time. This type of receiver converts the incoming frequency from the receiver’s antenna to a fixed frequency.Ĭonstant Selectivity and the Superheterodyne ReceiverĪs discussed in Part 1 of this series, as the frequency of a single or coupled tuned circuits is increased, the selectivity decreases to the point that there may be insufficient selectivity at the higher frequencies being tuned. ![]() As discussed in Part 1 of this series, as the frequency of a single or coupled tuned circuits is increased, the selectivity decreases to the point that there may be insufficient selectivity at the higher frequencies being tuned. ![]()
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