Greetings

I have been reading about this new? broadband antenna... It seems mainly
used in the short wave receiver domain but I also find newly licenced
amateur also using it...

It is a spin-off of the 'end fed' antenna but seems to have some point
blurred in the translation.....

The antenna is constructed as follows....

A random length of wire any where from 40 feet to 140 feet.. The end nearest
the house is connected to one end of the high impedance end of a 9 to1
balun.. The other end of this end of the balun is connnected to ground...

The arguement is that because the high impedance end is connected to ground
that the antenna is quieter...less noise...

The low impedance end of the balun is connected, via a length of 50 ohm
cable, to the receiver... or transceiver...

The other end of the cable is connecte to the receiver or transceiver and
needs to use an antenna coupler.....

My question.. is this a valid antenna....

Personally, I don't think so...

I beleive that because the antenna comes to the radio in 50 ohm coad but
still needs an antenna coupler the swr must be high therefore the antenna in
not valid...

Someone suggested that this design is a spin-off of an end fed dipole or
zepp ...but I disagree...I think there are a few points missing for it to
qualify as an end fed dipole or zepp...

Larry ve3fxq

anyways.. any thoughts?...

On Mon, 1 Aug 2005 14:49:32 -0400, "larry" wrote:

I beleive that because the antenna comes to the radio in 50 ohm coad but
still needs an antenna coupler the swr must be high therefore the antenna in
not valid...

Hi Larry,

An antenna coupler for either SWL or Ham use is distinctly indicated
for this "broad band" antenna. It is only broad band if it can be
distinctly used across a broad band (this maybe someone's idea of 5KHz
or 50MHz).

Someone suggested that this design is a spin-off of an end fed dipole or
zepp ...but I disagree...I think there are a few points missing for it to
qualify as an end fed dipole or zepp...

Well, shy a few points is not distinctive enough to dismiss the design
from the end fed dipole or Zepp categories. Suffice it to say that at
some frequencies, and with the right matching, you could not
distinguish this antenna from them (insofar as results go).

73's
Richard Clark, KB7QHC

Greetings to you Larry,

Any length of wire is a 'valid' antenna. i.e., it is sure to work.

If it's a short wire it will have sharply resonant frequencies and
will not be broadband.

If it's long enough, and its normal attenuation is high enough, it
behaves as a transmission line and its input impedance will eventualy
converge on the line Zo. Depending on height above ground, on wire
diameter, and on the general environment, Zo will be roughly resistive
between 500 and 600 ohms.

You then have your wideband antenna. A 9-to-1 matching transformer
reduces the impedance to about 60 ohms which is very nicely between 50
and 75 ohms. So you can take your pick of what impedance receiver you
use.

If the antenna is not very long in terms of wavelengths, or even if it
is, it can be terminated, at the remote end, to ground with a 560-ohm
resistor and then the antenna will have an input impedance of about
560 ohms all the way from DC up to many, many MHz. Which is wideband
enough to keep everybody happy.

Unfortunately the antenna's radiation pattern is many-lobed in the
direction of the wire. When terminated it is highly uni-directional
which is unlikely to be of much use to most people. It will nearly
always be in the wrong direction. Which is why it is not very popular
except for static, specialised, point-to-point LF communications.

It's really quite simple. Try not to be distracted by
over-complicating experts on reflected and non-reflected power and
standing waves.

Actually there is a name for such a wideband antenna. But I can't
think of it at the moment. It may be the early symptoms of Alzeimers.
----
Reg, G4FGQ

Where did you read about this antenna ?
Receivers can withstand a lot more swr than transmitters, so it should work
fine for swl.
Compared to no antenna, its great.
It might work better if you had an antenna tuner between the antenna and the
radio.

"larry" wrote in message
...
Greetings

I have been reading about this new? broadband antenna... It seems mainly
used in the short wave receiver domain but I also find newly licenced
amateur also using it...

It is a spin-off of the 'end fed' antenna but seems to have some point
blurred in the translation.....

The antenna is constructed as follows....

A random length of wire any where from 40 feet to 140 feet.. The end
nearest
the house is connected to one end of the high impedance end of a 9 to1
balun.. The other end of this end of the balun is connnected to ground...

The arguement is that because the high impedance end is connected to
ground
that the antenna is quieter...less noise...

The low impedance end of the balun is connected, via a length of 50 ohm
cable, to the receiver... or transceiver...

The other end of the cable is connecte to the receiver or transceiver and
needs to use an antenna coupler.....

My question.. is this a valid antenna....

Personally, I don't think so...

I beleive that because the antenna comes to the radio in 50 ohm coad but
still needs an antenna coupler the swr must be high therefore the antenna
in
not valid...

Someone suggested that this design is a spin-off of an end fed dipole or
zepp ...but I disagree...I think there are a few points missing for it to
qualify as an end fed dipole or zepp...

Larry ve3fxq

anyways.. any thoughts?...

Larry,
Is it a 'valid' antenna? Ah, yes, with several 'buts' that
'add to' / 'subtract from' that 'validity'. The 'biggy' questions
are what length and what frequency of use? Those will determine
the input impedance of the thing, and who says that a 9:1 is
going to be the 'right' impedance transormation ratio? That
9:1 thingy is basically taking the place of a tuner, which would
make the thing a much more 'valid' multiband antenna, but not
necessarily a very broadbanded one.
So while there is some validity, I don't think I'd say it was
totally valid, broadbanded, or multibanded. Not bad advertising
though...
'Doc