THE HALF WAVE VERTICAL
the best know antenna on our 11 meter band !
Everyone has used this type in the past or will use it somewhere!
Although the half wave vertical comes along with various
names the PRINCIPLE is all the same.
The only (electrical) difference, is how the 50 ohms from the coax cable
is brought over to the antenna and visa versa.
The reason why this antenna type is so popular are probably the following:
The length is "only" about 5,50 meters
This antenna does not require any radials
Easy to erect!
To construct this antenna most use black markings on the aluminum to
judge the length and give the user a satisfying S.W.R.
But there are also those who use other technics to control the S.W.R.
in such away that it becomes possible to change the SWR from the bottom
of the antenna.
behind this antenna is quite simple, its as the name says a half wavelength
long tube or wire with its feeding point at the end.
With that comes a high impedance, we overcome that problem by putting
in a transfer device to put that impedance back to around 50 ohms. This
always includes some type of a coil. It can be a small one made on a
print for or a strong solid one. Be carefully with those "print"
coil types, they can not handle high power.
HOW HIGH SHOULD I PLACE THE 1/2 Vertical ?
The following diagrams are constructed over good ground.
In the first diagram we see that the take-off angle is quite low (A-16
degrees) while the antenna is only a half meter above the ground!
In the second diagram (B) where the antenna is situated 6 meters above
the ground, we see that the take-off angle is in the order of 35 degrees
but still at 16 degrees its only several dB's down to the lower one.
This means for Real long distance DX the lower antenna will be better
of most of the time. In the summer months with the sporadic E openings
the antenna situation B will be better most of the time.
When we come to a height of 15 meters we reach the same thing the angles
C and D are almost the same as angle A and B .
When the antenna is put as high as 25 meter above the ground the lowest
angle is around 5 degrees (G) and there are several side-lobs higher
A vertical (half wave) almost sitting at the ground IS capable of working
DX! ( better then any horizontal antenna at that height! )
But placing a half wave vertical much higher is not always favorable.
For this height reason, DX-expeditions sometime favor vertical antennas!
Although there are those who sell an additional radial kit there is
almost no difference when you add these radials to the antenna
This antenna-type does not require one.
Another issue is the gain, since it's electrical length is only a half
wave. You can look to it as a Dipole (only end fed),
Now you'll probably realize that the antenna does not have the gain
many manufacturers would like you to think it has, measured the right
The gain of the antenna is 2,14 dBI in free space.
There is NO WAY you can produce 10dBI or more from these kind of antennas.
If anyone can produce this there will be no use for a 5 or 6 elements
it is of no influence how pretty the antenna is with fiberglass/without..there
are those with light bolds on top etc etc..don't care about that. The