When elevated radials are mentioned they are often full 90-degree radials. The low impedance presented by the radials makes decoupling the coaxial cable shield easy. The counterpoise current will div
Unfortunately, not. As an EZNEC computation can show, even with a large number of elevated 90-degree radials, there can be a lot of common mode current, and balun requirements are much stronger than
Maybe easy, but decoupling is still necessary if you want a clean and reliable installation. The notion a few 1/4 wl radials result in a perfectly unbalanced antenna is clearly false. A commercial 4
Sinisa, I should have included some numbers to show the magnitude of the effectiveness of tuned shortened top band radials. To answer the point of Tom W8JI, for a 40 meter ground plane up 20' and hav
With elevated radials near earth there can be a dB or more FS reduction when the feedline shield is not decoupled. This says nothing about the unwanted coupling of noise into the antenna, or RF into
when the feedline shield is not decoupled. This says nothing about the unwanted coupling of noise into the antenna, or RF into other devices close to the feedline or operated from the power line. <<
SM0MDG: >> To decople my my inverted L I was using a RG213 coil made of 18 turns on a 11 cm plastic pipe. Would this arrangement be enough to decouple my top loaded vertical with 2 elevated radials?
Dave, Thanks for the example, it is very good reading! I agree it would be useful to measure the feed line current, but what I have at hand is a Palstar ZM30 analyzer, a multimeter and a RF probe. I
Bjorn, is the RF current probe opening large enough to clamp around the coaxial cable? If it is then you are ready to measure. If the RF current probe opening is too small you can use a large ferrite
difference. << Update: I added the choke at the antenna base. Before doing that I created a probe by wounding abt 15 turns of enamelled wire around the coax close and localised a point on the coax w
Update: I added the choke at the antenna base. Before doing that I created a probe by wounding abt 15 turns of enamelled wire around the coax close and localised a point on the coax with a maximum re