Thanks Alyson for that information!
I guess if you take any antenna with 15 dB ?of gain and then throw in 3DB of loss, you still have 12 DB of gain!
In order to make my non-resonant dipoles tune with an MFJ auto tuner on?just about any frequency, I almost always end up with a problem at one particular band, usually where the antenna is a full wavelength long.
I gave up, and just put in simple traps made out of RG 58 coax. ?Undoubtedly, that adds some loss & ?I think it¡¯s worse near there resonant frequency I¡¯m told, but I still think I¡¯m probably better off than having an actual big resistor ?somewhere. ? The
compromise of coarse is I have to spend a couple hundred dollars on a fallible auto antenna tuner. ?So that¡¯s a compromise!
But I think I have lower loss most of the time. ?My gateway station get plenty of use, so it must be doing something right.
Gordon. ?
On May 12, 2018, at 14:29, ajparent1/KB1GMX <
kb1gmx@...> wrote:
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Any time you include a resistor you loose some efficiency.? ? Having designed mil antennas usually
the source tolerates some maximum SWR without a tuner typical is 2.5:1? some its 3:1.? However
where you put the resistor and how you construct the system as a whole is important.? The B&W
is simple and does work and generally for various bands its not bad for the long version.? Like
all antennas the short version does NOT have the same low frequency capability and will be lossy
there.
As to modeling it, beware dragons may lie beyond.? The most common error is that NEC (V2)
does not alway shandle two parallel wires correctly if they are close.? The result then is invalid.
I've done an eval using the NEC4 engine and even then you have to pay attention to wires
close spaced though it handles it better.? Folded dipoles are tricky to model.
There are resistor loaded antennas that offer gain and are considered wideband as well.
One that comes to mind is the Rhombic.
Allison
