I have a simple transmitter that uses an oscillating coil to determine the frequency. How do I increase the frequency because it does not reach the upper end of the range even when I open the entire trimmer?
To increase the frequency of an oscillator that uses a coil and a capacitor, we have two possibilities. The first is to separate the coils from the coils, ie stretch the coil. In this case we have a small change, but usually enough to shift the frequency within a not very wide range. The second, which allows a higher frequency increase, is to take turns, ie to cut the coil so that it has fewer turns. This procedure is also valid for single tuning circuits. For superheterodyne type radios, however, when we change the antenna coil we also need to change the oscillator coil accordingly and then the whole set needs a good adjustment. Even so, changes made to commercial circuits lead to sensitivity imbalance at the extremes of the range.
