Here is my first reliable and still working Yagi antenna for my radios PMR446, 14 elements, 2.5 metres long, gain 13.6 dBd.
I homemade this antenna spending 0 €, recycling two old VHF TV antennas and a broken clotheshorse and a piece of wood.
Here is the Yagi antenna ready. I inserted the elements because I have a poor drill column and the holes were // instead of ||. Elements are glued with hot glue (previously I used silicon but it was too much rubbery and when I transported the antenna in my car, the elements detached) and all the elements are on the same plane. Simple and a perfect result.
In this manner, I resolved another problem: feeding the dipole. Simply I made a hole perpendicular in the boom's center, passed the cable RG58 and connected at the dipole with two screws selfthreading...
The antenna support was recycled from my previous Yagi antenna 13 elements, in turn recycled from a broadband UHF TV antenna. Nothing creates, nothing destroys, all transforms itself...
All the elements of this Yagi antenna are made of solid aluminium, only the dipole elements are made of aluminium tube, recycled from clotheshorse, so that in a moment, with a vice, I pressed the ends where I connected the cable RG58. The feed point is an open dipole, without balun... And all the elements are inserted in the wooden boom, no insulators needed.The space between the dipole elements is 1 centimetre and the two little pieces of cable where there are the screws are perfectly equal, so to minimize the unbalance between coaxial cable and dipole.
...A lot of people asked me to explain, in an easy way, how to build an antenna like this one. It's very easy:
first of all, go to k7mem's site, it's all easily explained. In the frequency field, you have to insert 446 MHz, of course...
For your boom, you can use whatever you want, a metallic, plastic or wooden one, a broomstick, use your fantasy!
The only thing you have to take care is precision and mount the elements in the right order.
Below, there are the specifics of this yagi antenna for PMR446 calculated for 446.1 MHz (channel 8) from the site of k7mem:
|element (diam 6mm)||length mm||cumulative spacing mm||gain dB over dipole|
|director #12||259.50||2429.39||13.6 (this yagi)|
Looking at the table, we can see a very interesting note: for doubling the gain (+3dB) we need to double the number of elements and more than double the lenght of the boom. But, handling a 2.5 metres antenna is not like handling a 6 metres long one... so, maybe it's better to stack another "little" antenna.
I renamed my site "www.fucimin.altervista.org" to "www.fucimin.tk". Would you like to do the same with your site too? It's simple and free!