The inductor for the output stage of the transmitter with a parallel power, a very important detail that can cause a number of unpleasant phenomena, from excitation to spontaneous combustion.
Made in the traditional way a choke that works on multiple ranges, represents an optimal quarter-wave line, for the low frequency range. Frequency half-wave resonances for other, more short-wave bands, often located near the operating frequency of the transmitter, which leads to trouble.
Using a ferrite core with sufficient initial permeability, it seems possible to manufacture a choke whose first half-wave resonance will be located outside the Amateur radio bands.
So, the inductor wound on a ferrite core with a permeability of 600...800, diameter 8 mm length 72...75 mm. the Wire of 0.45 sew-2. Winding a length of 40 mm solid, 25 mm - progressive increments of 0.5 to 4 mm (about 15 turns). 95 turns. The first half-wave resonance of the inductor is at a frequency of 32 MHz. The inductance at a frequency of 1 MHz is 300 mH. This ensures a perfectly acceptable options in the range of from 1.5 to 30 MHz without resonances.
Author: O. Puzanov (UB5LW); Publication: N. Bolshakov, rf.atnn.ru