ANTENTOP- 01- 2006, # 008

Indoor Helical Antenna

Antenna Adjustment at 20 meters Band: Above all, stay your K-1 to 2W. Antenna (spiral at first it is not spreading by the stick) is connected to K1 by a small (50- 70 cm) length of a coax. A small bulb is connected in serial with the spiral. I have used a bulb from a toy gun feeding from 3V. Turn on K1 to receiving mode to the 20 meters. With help of a dielectric stick (I used a length of a plastic water pipe) in 1 meter length lift upwards the spiral. Find off the spiral length when you have the best reception. Do a hole in the stick at the length and pass through the hole the end of the spiral. After that once again with the help of the dielectric stick, approximately on the length of 2/3 (from spiral length) from the antenna bottom, lift or lower coils of the spiral by the best reception. Coils are fastened by Scotch at the proper place. After that you may turn on K1 to transmitting mode (for a short time) and to make final adjustment of the spiral (by max glow of the bulb) at the length of 1/3 (from spiral length) from the bottom. Coils are fastened by Scotch at the proper place.

Fastened coils

Antenna Adjustment at 17 meters Band: Prepare a 60 cm length insulated wire (18 AWG) with crocodile clips at the both ends. Connect to K1 the antenna and turn on it to RX. Short different parts of the spiral by the best reception.

Antenna hung up to eave

Fastened the Spiral to the Form

Turn on K1 in TX and check the antenna by glow of the bulb. Put marks by marker at the shortened coils. You can turn on the wire to the marked coils when work at 17 meters band.

Figure 1 shows a final design of the helical antenna. Short the bulb by a crocodile clip when you want work to transmit or you lose RF power in the glow bulb.

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