Several authors recommend against
end-fed dipoles because of alleged
difficulties in matching to a 50-ohm
line. Unfortunately, the "slur" is
dropped without a hint of explanation.

Other authors see it as simple and
reliable, and recommend it with enthusiasm.

A parallel tuned circuit with tapped
inductor is usually the recommended
impedance transformer.

In my own experience, matching has
always been extremely easy and
trouble-free. So does anyone know why
this might be thought so frought with
problems that its general use would be
discouraged?

Chuck, NT3G

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On Mon, 18 Jun 2007 10:42:08 -0400, Chuck
wrote:

In my own experience, matching has
always been extremely easy and
trouble-free. So does anyone know why
this might be thought so frought with
problems that its general use would be
discouraged?

Hi Chuck,

The slur may attend the illusion that just the antenna is being
matched and the operator cries foul about transmission line common
mode currents.

However, if those currents go unnoticed; then end fed antennas are
marvelous and have this undeserved bad reputation. On the other hand,
if those currents are noticed and fixed, the antenna probably doesn't
work any better; but after all that effort "it damned well should and
no one is going to convince me otherwise."

73's
Richard Clark, KB7QHC

One other thing, I see, is that End Fed Dipoles
have a extremely high impedence, and hence a very
HIGH VOLTAGE (altho at little current), unlike
center-fed dipoles. Might make insulation
problematic to prevent arcing . Can generate
hundreds (if not Thousands) of volts, at the feed
point! Jim NN7K

Richard Clark wrote:
On Mon, 18 Jun 2007 10:42:08 -0400, Chuck
wrote:

In my own experience, matching has
always been extremely easy and
trouble-free. So does anyone know why
this might be thought so frought with
problems that its general use would be
discouraged?

Hi Chuck,

The slur may attend the illusion that just the antenna is being
matched and the operator cries foul about transmission line common
mode currents.

However, if those currents go unnoticed; then end fed antennas are
marvelous and have this undeserved bad reputation. On the other hand,
if those currents are noticed and fixed, the antenna probably doesn't
work any better; but after all that effort "it damned well should and
no one is going to convince me otherwise."

73's
Richard Clark, KB7QHC

On Jun 18, 4:09 pm, Jim - NN7K wrote:
One other thing, I see, is that End Fed Dipoles
have a extremely high impedence, and hence a very
HIGH VOLTAGE (altho at little current), unlike
center-fed dipoles. Might make insulation
problematic to prevent arcing . Can generate
hundreds (if not Thousands) of volts, at the feed
point! Jim NN7K

Then you have to have a pretty good tuner..
Along with whatever losses it provides..
I avoid tuners if at possible. None of my
everyday antennas use one.
I have a 989c, but I mainly use the wattmeter,
and switch..
The tuner itself sees little use. Probably has
spiders inside.. :/
MK

On Jun 18, 8:42 am, Chuck wrote:
Several authors recommend against
end-fed dipoles because of alleged
difficulties in matching to a 50-ohm
line. Unfortunately, the "slur" is
dropped without a hint of explanation.

Other authors see it as simple and
reliable, and recommend it with enthusiasm.

A parallel tuned circuit with tapped
inductor is usually the recommended
impedance transformer.

In my own experience, matching has
always been extremely easy and
trouble-free. So does anyone know why
this might be thought so frought with
problems that its general use would be
discouraged?

Chuck, NT3G

The matching doesn't have anything to do with it.
It's the excess common mode currents that I don't
like.
Sure, they work, but I would never use one if
I can center feed the antenna. And I've never really
had a case where I couldn't center feed.
MK

Correct me if I am wrong, but if you end feed a wire, it isn't a
dipole, its a monopole.


On Mon, 18 Jun 2007 10:42:08 -0400, Chuck
wrote:

Several authors recommend against
end-fed dipoles because of alleged
difficulties in matching to a 50-ohm
line. Unfortunately, the "slur" is
dropped without a hint of explanation.

Other authors see it as simple and
reliable, and recommend it with enthusiasm.

A parallel tuned circuit with tapped
inductor is usually the recommended
impedance transformer.

In my own experience, matching has
always been extremely easy and
trouble-free. So does anyone know why
this might be thought so frought with
problems that its general use would be
discouraged?

Chuck, NT3G

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--
73 for now
Buck, N4PGW

www.lumpuckeroo.com

"Small - broadband - efficient: pick any two."

"Chuck" wrote in message
...
Several authors recommend against end-fed dipoles because of alleged
difficulties in matching to a 50-ohm line. Unfortunately, the "slur" is
dropped without a hint of explanation.

Other authors see it as simple and reliable, and recommend it with
enthusiasm.

A parallel tuned circuit with tapped inductor is usually the recommended
impedance transformer.

In my own experience, matching has always been extremely easy and
trouble-free. So does anyone know why this might be thought so frought
with problems that its general use would be discouraged?

Chuck, NT3G

Take a google at "J-Poles" - an end-fed half-wave. (I'm reluctant to call it
a dipole.)
The 2-meter version of the j-pole is used by bunches of folks.
The matching section at the bottom allows hooking it up to 50-ohm cable.
I have not tried it on lower frequencies. But hey - making antennas is fun,
so get hold of an antenna analyzer, and play
eee ha

Thanks for interesting comments by all.

My question was prompted by reports of
alleged matching difficulties, rather
than by questions of general utility,
feasibility, or ancillary problems. For
example, Lee's Vertical Antenna Handbook
discusses various conventional matching
circuits for vertical antennas. For the
half-wave vertical, he comments tersely
that "It is difficult to match well and
should be avoided if possible". (page
25, 2d edition; context makes clear he
is referring to end- or base-feeding) He
shows the usual parallel tuned circuit
with tapped inductor as the appropriate
matching device.

Although Lee doesn't logically link his
assertion of matching difficulty with
his admonition of avoidance, he
conjoined them in the same sentence with
abandon or intent. My interest is
limited to the allegation of matching
difficulty.

BTW, I was assuming a half-wave,
horizontal antenna, one end of which is
brought directly into the shack with no
intervening transmission line.
Definitely not a dipole, but not a
monopole either, I suspect. There are
some reports out there of RF in the
shack with this arrangement, but
who has experienced matching problems?

So if there were no common mode issues,
the directly end-fed, half-wave wire
would be an equal opportunity candidate
along with the traditional dipole for
the same radiator geometry? Or is that
like saying if it weren't for gravity I
could fly?

73,

Chuck

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On Tue, 19 Jun 2007 09:16:30 -0400, Chuck
wrote:

BTW, I was assuming a half-wave,
horizontal antenna, one end of which is
brought directly into the shack with no
intervening transmission line.
Definitely not a dipole, but not a
monopole either, I suspect.

Hi Chuck,

It is merely an off-center dipole that hasn't come out of the closet.
The wiring in your shack supplies that other half, and supports the
common mode current/voltage.

There are
some reports out there of RF in the
shack with this arrangement, but
who has experienced matching problems?

The complaints made here are far from sparse. On the other hand,
those who don't notice, don't complain. I will bet you have one
outlet in your home with inverted neutral/hot and a floating ground.
Does it bother how your lamp works? Plug in a toaster and reach for
the faucet and the morgue attendant will tie a nice card to your toe.

Some folks have common mode complaints, others don't.

So if there were no common mode issues,
the directly end-fed, half-wave wire
would be an equal opportunity candidate
along with the traditional dipole for
the same radiator geometry? Or is that
like saying if it weren't for gravity I
could fly?

For wires less than 5/8ths (end-to-end), you have to work (or screw
up) damned hard to gain or lose half a dB from the typical lobe
geometry. I will be generous and call it a whole dB, but that is
barely the width of your S-meter's needle. There are other things to
worry about in life, like that outlet with a floating ground. In that
vein, you stand to come out ahead if you seriously examine your
shack's quality of ground for all applications.

73's
Richard Clark, KB7QHC

Hello Richard,

Richard Clark wrote:
It is merely an off-center dipole that hasn't come out of the closet.
The wiring in your shack supplies that other half, and supports the
common mode current/voltage.


Interesting concept. Not technically a
dipole, though. But similarly true of
less-than-perfect, center-fed dipoles, no?


The complaints made here are far from sparse.

I've seen no complaints here at all
about matching difficulties. Even
posters who had used the antenna omitted
matching difficulties from their
reported experiences.

On the other hand,
those who don't notice, don't complain. I will bet you have one
outlet in your home with inverted neutral/hot and a floating ground.
Does it bother how your lamp works?

I understand. But I really hoped to talk
about matching difficulties and find
myself awash in discussions of potential
common mode currents, about which I have
no truck. ;-)

Some folks have common mode complaints, others don't.

Sure. And I'd extend that to real,
center-fed dipoles with less than
perfect transmission line/antenna
symmetry. All a matter of degree?


For wires less than 5/8ths (end-to-end), you have to work (or screw
up) damned hard to gain or lose half a dB from the typical lobe
geometry. I will be generous and call it a whole dB, but that is
barely the width of your S-meter's needle. There are other things to
worry about in life,

Agreed.

like that outlet with a floating ground.
In that
vein, you stand to come out ahead if you seriously examine your
shack's quality of ground for all applications.

I'd do it immediately if it would help
explain the alleged matching
difficulties. ;-)

73,

Chuck

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