How about this one. Here is a top down view of an antenna radiation pattern when there is just 1 antenna. this first picture shows you how if you can't mount the antenna direct in center of the mass, the shape of the car body affects the pattern.
Now by co-phasing 2 antenna on side of vehicle, the pattern changes as shown below.
Also an antenna is a length of wire (no need to show the math).
in CB frequencies this length is too tall for most applications so they build the antenna with a coil of wire so it still has long wire length, but is shorted physically by the coil
An antenna as a straight wire transmits from the center of that wire.
Now add a coil to the antenna and you change where the electrical center of the wire is on the physical antenna.
Here is what I like about the designs like fire stick uses.
the whole antenna is wound, but the coil is at the top, this raises your physical transmission location to the center of the wire. While it may not raise it much, it raises it enough to get the antennas electrical center above the affects of steel car parts.
in an earlier post I talked about ground plane, I could have used the word
Counterpoise instead.
Now by co-phasing 2 antenna on side of vehicle, the pattern changes as shown below.
Also an antenna is a length of wire (no need to show the math).
in CB frequencies this length is too tall for most applications so they build the antenna with a coil of wire so it still has long wire length, but is shorted physically by the coil
An antenna as a straight wire transmits from the center of that wire.
Now add a coil to the antenna and you change where the electrical center of the wire is on the physical antenna.
Here is what I like about the designs like fire stick uses.
the whole antenna is wound, but the coil is at the top, this raises your physical transmission location to the center of the wire. While it may not raise it much, it raises it enough to get the antennas electrical center above the affects of steel car parts.
in an earlier post I talked about ground plane, I could have used the word
Counterpoise instead.
I used half a mirror arm mount bolted to about 3"x6 plate, clamping the roof rack.
Could not tell you why it works but it does. Electrically the rack is connected to aluminum frame so it is grounded. However I use small magnetic antenna so its only grounding thru the magnetic field. Not optimum but functions.
As far as ground 'plane' do not know whats its using. I assume its the height that compensates for otherwise poor mounting. Using everything underneath as the plane.
Most mounts the shielding sheath of coax also carries ground which is connected to base-typically mounted and its grounded.
Could not tell you why it works but it does. Electrically the rack is connected to aluminum frame so it is grounded. However I use small magnetic antenna so its only grounding thru the magnetic field. Not optimum but functions.
As far as ground 'plane' do not know whats its using. I assume its the height that compensates for otherwise poor mounting. Using everything underneath as the plane.
Most mounts the shielding sheath of coax also carries ground which is connected to base-typically mounted and its grounded.
