NVIS antenna question
 

For those of you who are very experienced on NVIS antennas, I have a
question:

How would a 450ohm fed (with manual tuner) 75M dipole at 15' height
compare to a standard 50ohm coax fed 75M dipole at same height? Would the
open feedline method reduce 75M performance compared to the regular coax
fed NVIS dipole?


Ed K7AAT

I ask this because I would find it useful to use the 75M NVIS dipole also
on 40M.

Would the
open feedline method reduce 75M performance compared to the regular
coax
fed NVIS dipole?

Yes, slightly. But not enough to really worry about if you are
careful tuning, and use the least inductance setting. But yes,
unless the coax fed is hundreds of feet long, or thin junky
coax, usually it's the least overall loss on HF. I use fanned out
dipoles for
separate bands fed with one coax. MK

Ed wrote:
How would a 450ohm fed (with manual tuner) 75M dipole at 15' height
compare to a standard 50ohm coax fed 75M dipole at same height? Would the
open feedline method reduce 75M performance compared to the regular coax
fed NVIS dipole?

450 ohm ladder-line feeding a 50 ohm load has approximately the
losses as RG-213 feeding a 50 ohm load so you would not be able
to tell the difference in performance. However, you may have
trouble matching the ladder-line at the transmitter unless you
make it 1/2 wavelength long. How long will your ladder-line be?
--
73, Cecil http://www.qsl.net/w5dxp

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450 ohm ladder-line feeding a 50 ohm load has approximately the
losses as RG-213 feeding a 50 ohm load so you would not be able
to tell the difference in performance. However, you may have
trouble matching the ladder-line at the transmitter unless you
make it 1/2 wavelength long. How long will your ladder-line be?


Lenth of feedline is yet undetermined as I have not yet considered final
antenna location on my forested 2 acres, nor route of feedline. Due to
foalage, I may stick with coax, anyway.....


Ed