After long time, I had an irresistible desire of fix my 14 elements homemade antenna, destroyed during the moving of our house: elements were detached and I was tired to reattach them with hot glue.
Now, I own a pillar drill and finally I'll can do a decent and lasting job.
Before of doing wrong holes into the poor antenna boom, I played a little with that fantastic and free software called 4nec2.
Here are the features, calculated with dimensions from the K7MEM's site, simulation was done rounding the real dimension at the millimetre. In short I saw that doesn't change nothing from holding all decimal after the millimetre:
We can note that this antenna isn't in perfect resonance. Then I asked myself if I could optimize a little bit this antenna just to obtain the resonance at frequencies of our interest, that means that little slice of frequencies ranging from 446 to 446.1 MHz, the remainder we aren't interested in. So, I played a little with reflector and dipole lenght and with the relative distance and here is the final result:
Wow: now I really like it! This will be the last release of my 14 elements Yagi antenna. Gain remains the same, as the front to back ratio, the impedance dropped to 50 ohm but the more important thing is that now the antenna is perfectly in resonance :-).
For curious guys, below I put the .nec files relative at the study of the two Yagi antennas for PMR446 band just analized:
Next, I'll change the feeding system: no more the cable directly connected to the dipole but a coupling balanced/unbalanced with a 1/4 wave cable. And now get down to the work!