I'm interested in attempting my own base loaded antenna, starting with something common like 11 meters. I know I can buy one but I am interested in the theory.
I have been experimenting with mounting positions of a cheap Cobra HG A1500 antenna. It has made me wonder what the difference is between it and something like a Wilson 5000 or a Stryker SR-A10.
I know mag base antennas are not efficient and I understand the ground plane issues / antenna length related to wavelength, etc. I have a nano VNA as well.
I was reading about loading and how the purpose of the coil is to physically shorten the antenna, but keep it electrically the same as whatever wavelength. I have demonstrated this with the two wire examples below. They are the same length, but one is shorter because of the coil.
I also saw a discussion of how the rf actually radiates with the coil placement. Most agreed that the majority of the rf radiated from the mast in the area below the coil - in a center loaded antenna. The claim is that these are better if you have to use a shorter antenna with a coil, center loaded was best.
This struck me as odd, because the base loaded antennas have the coil at the base. Where does the rf radiate from on these units?
Also curious what makes the more expensive base loaded units tick, what makes them better than a standard mag base, etc etc.
I have an example below of how I understand it (which very well could be wrong). I picture the coax going into the base with the center conductor connecting to the coil itself. The coil itself has a socket of some sort, which accepts the mast or whip. When the mast and coil are connected, the length is then electrically correct, but physically shorter.
The shield is terminated within the magnetic base, but to nothing really important from the few i’ve taken apart.
Do I understand this correctly?
I have been experimenting with mounting positions of a cheap Cobra HG A1500 antenna. It has made me wonder what the difference is between it and something like a Wilson 5000 or a Stryker SR-A10.
I know mag base antennas are not efficient and I understand the ground plane issues / antenna length related to wavelength, etc. I have a nano VNA as well.
I was reading about loading and how the purpose of the coil is to physically shorten the antenna, but keep it electrically the same as whatever wavelength. I have demonstrated this with the two wire examples below. They are the same length, but one is shorter because of the coil.
I also saw a discussion of how the rf actually radiates with the coil placement. Most agreed that the majority of the rf radiated from the mast in the area below the coil - in a center loaded antenna. The claim is that these are better if you have to use a shorter antenna with a coil, center loaded was best.
This struck me as odd, because the base loaded antennas have the coil at the base. Where does the rf radiate from on these units?
Also curious what makes the more expensive base loaded units tick, what makes them better than a standard mag base, etc etc.
I have an example below of how I understand it (which very well could be wrong). I picture the coax going into the base with the center conductor connecting to the coil itself. The coil itself has a socket of some sort, which accepts the mast or whip. When the mast and coil are connected, the length is then electrically correct, but physically shorter.
The shield is terminated within the magnetic base, but to nothing really important from the few i’ve taken apart.
Do I understand this correctly?
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