A simple antenna
In some cases, when for some reason you can't build a complex antenna type "wave channel", which gives the best results in the 144 MHz band, it is possible to apply the whip antenna, which is simple in construction and does not require rotating mechanism, since its radiation is not directed.
The antenna design is shown schematically in Fig. 1. Emitter 1 with a length of 525 mm of copper or brass tube with an outer diameter of 8 mm is passed through the bushing 2 and is attached to the inner contact of the chip 3 of the coaxial connector. The external contact of the chips is connected with a rectangular base size H mm sheet steel or aluminum. To the four corners of the base are welded beams 5 length 490 mm of steel or aluminum rods with a diameter of 6 mm.
With strict observance of the above mentioned dimensions (length measured from the connection with the chip coaxial connector) output impedance of the antenna is equal to 60 Ohms.
To install the antenna in the attic between the rafters or on the mast. In all cases it should be placed as far as possible from metallic parts of the house, so as not to increase the losses.
Publication: N. Bolshakov, rf.atnn.ru