DIY Interphone Plus a sense of the antenna

The easiest way to free a coil around a metal radiator connected to the bottom, and then launched, with the standing wave table to see SWR, slowly correct number of turns, will use the following can be 1:1.5. Efficiency Well, not easy to say, you may do radiation only 0 false load.

Generally speaking length of 1 meter quarter-wave whip antenna on the handset for a few long, great inconvenience to users. Supporting small-scale method to the multi-handset helical antenna, its simple structure, like a length of spring; made ​​after a length of about 26cm or so, easy to use, production is also easy.
Operating frequency is set at 150MHZ:
Screw diameter D = 10mm, pitch = 3mm (distance per lap),
Helical turns N = 37 rings, spiral part of the required wire length L ≥ 116.2cm
Available spiral circle of diameter 0.8 ~ 1.2mm copper wire or wire wound.
Ready, open at one end, leaving the other end of the first axial plug into the antenna can be fixed.
These are calculated values​​, as mentioned above, before using the best test to use table tune about SWR, its minimum value, in order to obtain higher efficiency.

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