In receiving and transmitting short-wave equipment widely used high frequency inductors with inductance from several tens of microhenry to units of millihenry. If there is no standard radio chokes with ferrite magnetic core (D-0,1, etc.), you can use corrective choke tube TVs (as spares they are sometimes on sale). So in a unified black-and-white TVs of the second class there are chokes with inductance 39, 95, 140 and 360 µh. It's basically a coil wound around the way "universal" in the high-resistance resistors MLT-0,5 (see Fig. 1, a).
Fig.1
These inductors have ferrite magnetic core, so they (unlike chokes D-0,1) can be applied in circuits where there are relatively large high-frequency voltage, for example, in predominetly and sometimes even in the terminal stages of the transmitting apparatus. Such chokes easy to make yourself. In Fig. 1, b example of a self-made inductor with an inductance of 330 µh, developed under the printed circuit Board of the transceiver, "Radio 76 M2" (the distance between the holes in the Board for mounting - 15 mm). The constructive dimensions of the inductor shown in Fig. 2.
Fig.2
He wound on the bar section of 3 × 3 mm made of a sheet of organic glass, polystyrene, fiberglass, or any other good insulator. So as not to damage the wire insulation, the edges of the bar round off, and so that the turns of the coil together, you must install the cheeks of some of the dielectric (Fig. 2 they are shown by a dotted line, as in Fig. 1, b absent, were removed after pouring the coil paraffin). In block molded on two segments of tinned copper wire with a diameter of about 0.8 mm - future.
The required number of turns N can be estimated by the approximate formula
N=arene(L/d)
where L is the inductance of the inductor (µh), d - diameter of coil (mm). For the frames with the cross-section in the shape of a square in this formula instead of d should substitute a value of 1.2 a, where a is the side of the square.
To choke inductance 330 µh need to reel 310 turns of wire sew or PASO with a diameter of 0,1...0,2 mm (type of winding is in bulk). Specified in Fig. 2 the diameter of the coil corresponds to the wire sew-2 0,14. This inductor has a q-factor of approximately 50 (measured at a frequency of 0.3 MHz).
If acceptable external diameter of the coil (about 10...12 mm, as, corrective throttle from the TV - see Fig, 1, a) in this version it is possible to make the choke inductance to units of millihenry.
Author: A. Greeks, Moscow; Publication: N. Bolshakov, rf.atnn.ru