I'm confused about the requirements for a counterpoise for an end-fed wire antenna.

What are YOUR requirements? (What bands, how long is it?)

Apparently this is not as important as you first imagined.

"Art Unwin" wrote in message
...
On Aug 3, 5:24 am, Richard Fry wrote:
On Aug 2, 3:01 pm, Art Unwin wrote:

An end fed antenna cannot be of a fractional wavelength...

_________________

? ?

Art, note that the vertical monopoles used by MW broadcast stations
are ALL fractional-wavelength radiators, and probably 99% of them are
end fed.

I regard a radiator with a counterpoise as being center fed of a
given impedance to connect to regardles whether the counterpoise is
above ground or not. If a radiator is of a closed cuircuit form it may
be fed at any point in physical terms. Other peoples definitions may
vary.

This is a simplified way of looking at things. It only works if he is to
use a horizontal loop, but doesn't address matching the antenna to the line
and in the case of "two pieces of wire", you won't have a clue where the
electrical "center" is. One of the original posts was about a dipole where
the coax would have to follow one of the legs because it would hang down
where it shouldn't be. That makes the feed point NOT in the center and
prone to common mode currents on the line.

It took me a couple of posts to realize the Poster has made multiple posts
questioning different aspects of his problem and we get the whole scenario
from chasing down all his threads.

It looks to me that his real estate won't allow a balanced antenna anyway,
so he will have to deal with the issues of an unbalanced radiator anyway. I
first thought of an Inverted L as an optimal antenna for his situation, with
remote matching for multi-band operation to keep RF out of the shack. An
elevated horizontal loop or off center fed dipole with ladder line to a
tuner at the entrance of the shack would also be an answer to the problem.
A multi-band vertical would be a good choice for 30-10 meters. Although
they work for 40 and 80, the pattern is not as good as a horizontal antenna
for exploiting the shorter skip.

On Aug 3, 11:17*am, "JB" wrote:
"Art Unwin" wrote in message

...
On Aug 3, 5:24 am, Richard Fry wrote:

On Aug 2, 3:01 pm, Art Unwin wrote:

An end fed antenna cannot be of a fractional wavelength...

_________________

? ?

Art, note that the vertical monopoles used by MW broadcast stations
are ALL fractional-wavelength radiators, and probably 99% of them are
end fed.
I regard a radiator with a counterpoise *as being center fed of a

given impedance to connect to regardles whether the counterpoise is
above ground or not. If a radiator is of a closed cuircuit form it may
be fed at any point in physical terms. Other peoples definitions may
vary.

This is a simplified way of looking at things. *It only works if he is to
use a horizontal loop, but doesn't address matching the antenna to the line
and in the case of "two pieces of wire", you won't have a clue where the
electrical "center" is. *One of the original posts was about a dipole where
the coax would have to follow one of the legs because it would hang down
where it shouldn't be. *That makes the feed point NOT in the center and
prone to common mode currents on the line.

It took me a *couple of posts to realize the Poster has made multiple posts
questioning different aspects of his problem and we get the whole scenario
from chasing down all his threads.

It looks to me that his real estate won't allow a balanced antenna anyway,
so he will have to deal with the issues of an unbalanced radiator anyway. *I
first thought of an Inverted L as an optimal antenna for his situation, with
remote matching for multi-band operation to keep RF out of the shack. *An
elevated horizontal loop or off center fed dipole with ladder line to a
tuner at the entrance of the shack would also be an answer to the problem..
A multi-band vertical would be a good choice for 30-10 meters. *Although
they work for 40 and 80, the pattern is not as good as a horizontal antenna
for exploiting the shorter skip.

You are correct. I should NOT have given a simplified response to a
simple question.
Your technical answer is a much better response tho I suppose I could
have made mine as technical so that he would not ask questions any
more! Good point about common mode. That should screw him up as well
as other things that you inserted with respect to how does one connect
to an antenna. We could ask him I suppose how many wires he intends to
connect to his intended antenna feed point, and if it is not two then
question how he intends to measure the impedance for matching
purposes. Yup, I could have done a better job.

In article
,
Art Unwin wrote:

On Aug 3, 5:24*am, Richard Fry wrote:
On Aug 2, 3:01*pm, Art Unwin wrote:

An end fed antenna cannot be of a fractional wavelength...

_________________

? ?

Art, note that the vertical monopoles used by MW broadcast stations
are ALL fractional-wavelength radiators, and probably 99% of them are
end fed.

I regard a radiator with a counterpoise as being center fed of a
given impedance to connect to regardles whether the counterpoise is
above ground or not. If a radiator is of a closed cuircuit form it may
be fed at any point in physical terms. Other peoples definitions may
vary. The poster I understood to be at the position of the end of a
transmission line with two wires in hand and wanted advice from that
point to procede. If his advisers are going to quibble then he needs
to go elsewhere for advise or settle for a poll.

All this discussion of "counterpoise" should be centered around Single
Frequency Antenna Systems Design, and is NOT relative to multi-Band, or
Wider than 10% of Frequency, Bandwidth, End Feed Antenna Designs. These
latter Antenna Systems are not using a Counterpoise, as such, but REQUIRE
a LOW Impedance BroadBand RF Ground, which in most cases needs to be
built, on site, and engineered to provide that Low Impedance, Wide Band
RF Characteristics for the specific Radio System. Having spent a career
designing, installing, and operating LF/MF/HF Communications Stations,
all over the world, it isn't a trivial undertaking, should one actually
want the best Antenna System, possible, for any one location. There are
MANY factors to consider, with Ground Conductivity, Water Depth, changes
of these during the passing seasons, and Frequencies and Bands chosen
for communication links. In many cases an End Feed Vertical, just isn't
the best Antenna System for the location. In other cases, they can be
designed for really good efficiency and great propagation. On of the
best Systems I ever installed was a 70' insolated Tower, with a SEA-330
AutoTuner tied to the center of a 100 Sq Ft Galvinized Screen built in
the center of a One Sq. Mile Salt Marsh, that flooded every 12 hours on
High Tide. Rf Impedance was below 5 Ohms from 200 Khz, clear up thru 22
Mhz.

--
Bruce in alaska
add path after fast to reply

You are correct. I should NOT have given a simplified response to a
simple question.
Your technical answer is a much better response tho I suppose I could
have made mine as technical so that he would not ask questions any
more! Good point about common mode. That should screw him up as well
as other things that you inserted with respect to how does one connect
to an antenna. We could ask him I suppose how many wires he intends to
connect to his intended antenna feed point, and if it is not two then
question how he intends to measure the impedance for matching
purposes. Yup, I could have done a better job.


Art,

See the original post asking: "How to route feedline from dipole".
If he were to let his coax hang straight down from the feed point, there
would be no discussion. In asking about dressing the coax along one of the
dipole legs, Common Mode currents are induced on the outside of the shield
and there is no longer a simple discussion. His further questions arise
out of trying to deal with that problem of not being able to let his coax
hang where it wants to.

Also, one leg of his dipole will be over the roof and the other in the
clear, so one leg will be detuned to throw more trouble into the mix.

To get him on the air quickly, a tuner is desirable. If he has that, he
might as well make a multi-band antenna where his feed point location is
elsewhere. I think he got that because then he asked about counterpoise and
ground, which is the next step in the evolution of that type of system.

This is a specific technical problem.

"Wimpie" wrote in message
...
On 2 ago, 19:30, "KJ4NTS" wrote:
As you might know, the current that goes into the end-fed antenna
equals the current that goes into the counterpoise.

ONLY if the counterpoise is connected to the same location where the
'radiating' wire leaves the coax. if you run a piece of coax out the window
and connect just the center conductor to your end-fed antenna then connect
the 'counterpoise' to the radio ground lug as is commonly done, the current
in the counterpoise may be MUCH different than that going into the wire.

On 3 ago, 23:56, "Dave" wrote:
"Wimpie" wrote in message

...
On 2 ago, 19:30, "KJ4NTS" wrote:

As you might know, the current that goes into the end-fed antenna
equals the current that goes into the counterpoise.

ONLY if the counterpoise is connected to the same location where the
'radiating' wire leaves the coax. *if you run a piece of coax out the window
and connect just the center conductor to your end-fed antenna then connect
the 'counterpoise' to the radio ground lug as is commonly done, the current
in the counterpoise may be MUCH different than that going into the wire.

Hello Dave,

I supposed the counterpoise to be connected at same location as where
the antenna connects to the coaxial cable (so the cable is used as
feeder only). When you connect the counterpoise at the tuner, the
cable will be part of the radiating structure and, as you mentioned,
everything changes.

Best regards,

Wim