Recent content by HarryUSA

Now that I did the arithmetic, I see you are correct, 70cm is very close to 3/4λ, so yes, a 1/4λ antenna for 2M antenna will have a 50 Ohm feed-point, and so will the 70cm band since 3/4λ is also fed at a current loop.

First of all, how are you getting a 1/4λ ground-plane antenna to give you the proper input impedance on both 2M & 70cm? Unless you are using a 70cm trap, this is not possible as your input impedance at 70cm, for a g-p antenna, designed for 2M, would probably be over 400 Ohms, not 50 Ohms...

Unless you're going to use band traps, you will immediately run into a problem when you use the antenna on 80M, while on 160M your center-fed dipole is at a current loop, on 80M, each leg is now a 1/2 wavelength, and you are feeding each element at a high impedance point, eg., a voltage loop. So...

I said what the A99 antena really is; so to quote myself: "...to be clear, the Antron 99 is just a half wave antenna, with no less gain than a half wave dipole, and there is no way to get a radiator of one length to impersonate a radiator of another length." ...and I like it too.

I would imagine your transformer is actually an UnUn, if you're feeding an off-center-fed antenna. So you've said you can get to 45 feet in height, but what are your dimensions of the area you can have the antenna occupy?

Yes, a ground plane antenna has a low feed-point impedance because it is fed at a current loop, and that's because the antenna is a 1/4 wave length, or some odd multiple of 1/4 wave length. A J-pole is an end-fed 1/2 wave length antenna, making its input impedance and its radiation resistance...

While this is an old post, some things need to be addressed. First, the Antron 99 is a 1/2 wave antenna, and if anyone said that someone calls it a 1/2wave over a 1/4 wave, I can only imagine they were referencing the input impedance is the same as a 1/4 wave ground plane antenna, because a half...

The base of a J-pole is a high current point and if you're too close to ground, that current will couple with ground and/or your radials. So in conclusion, there would be no good that would come from radials, only height would help.