6 dB collinear VHF antenna
This is not very difficult to repeat УSW antenna with vertical polarization has a gain of 6 dB. Antenna "Slim-Jim" the most popular but has its gain only about 1.7 dB. I had problems with my station packet radio and I saw the output in increasing the antenna gain. So now I have the gain at 6 dB at УSW colinear.
This figure shows the basic design. There is nothing new here in technology. My antenna is made of 4 mm aluminum rods supported by nylon the pieces that I found in the kitchen (of course, when the house was not the wife). The length of each antenna element and the loop is calculated in polvani (1030 mm), but the plume longer by 5 cm flat Cable is bent so as to form two parallel conductors with distance between them of 5 cm. Two emitting remain straight vibrator. All three formed element (two vibrator and loop) are connected by means of two cut from nylon blocks.
I didn't show the sizes cut out nylon blocks, and inserted in the first picture only their form. It all depends on the design and dimensions of the wooden boom You have. This, of course, could be metal, but I was lying on the balcony a piece of wood that I used. It is only important that he was no shorter than 1/4 wave.
Insert the Central locking button (boom) first, then plug in the dielectric blocks all other elements (in this case they should enter with some effort). Vertical/horizontal holes at the ends of the unit must have electric the contact between the vibrator and train. I used to do this glandular segments wire (it sticks to the magnet) with the components of lead, which is good contact between the two elements. The copper wire should not be used, as with the time between it and the aluminum is formed corrosion.
The strength of the nylon block is more than sufficient to maintain all the elements even in strong winds.
The cable is attached at a distance of 15 cm from the short-circuited end loop. Loop powered 50-200 Ohm coaxial cable through a balun transformer. To do this, use the cable RG58 or URM76. Loop length forming the transformer shall be 0.33 wavelength. Half-wave radiating element for 145 MHz is $ 1030 mm, so the length of the coaxial the transformer should be about 345 mm (folded in half).
I recently saw a few articles published using the antenna this type of copper pipe. But I think my method is much easier and virtually worthless both in money and in effort (of course, if the wife You will not find in the kitchen for cutting off a piece of nylon).
Author: Harry Lythall (SM0VPO), Translated by N. Bolshakova.; Publication: N. Bolshakov, rf.atnn.ru