Offer more practical to use a variation of a helical antenna that replaces the helical antenna whip length 16 - 18 see the Radio station "without antennas", in addition to the extraordinary form, will be very compact. Made antenna in the form of a frame made of glued strips of Plexiglas the size of the housing of the radio station as a continuation of it in the upper part, as shown in the figure.
The frame antenna is attached to the housing of the radio station and can have various sizes depending on the size of Your radio. At the height of the frame 25 mm winding wire of 0.3 - 0.5 mm should start stepping back from the hull of 5 mm. This place will allow us to more precisely tune the antenna by moving the coils. The winding is performed to fill the frame in one layer. After setting up the coils covered with glue BF-2 and close the top cap is glued strips of plastic with a thickness of 1 - 1.5 mm, so that the cap did not differ by dimensions from the hull of the station. Attach the top cap to the body of radio can screw M2,5-MOH in the middle of the antenna.
To configure in the transmission, controlling the radiation level S-meter for another station to the antenna smoothly offer a hand. If the S-meter starts to decrease, unrolling and accusive 1 coil antenna and continue so on. After a while, having to put your fingers to the antenna, notice that the S-meter will first increase and then decrease with further approach of the hand to the antenna. This means that we are close to the resonance of the antenna. Further adjustment produced by gently pushing the coils of the antenna on the frame and achieving the maximum readings of the S-meter.
If at the beginning of the configuration hands on approach to the antenna, there is increasing evidence of the S-meter, then wound a few turns and you have to re-make winding a thinner wire to get on the same frame more turns. This method is suitable for setting all types of spiral antennas.
Author: A. Kucher; Publication: www.cxem.net