"Richard" wrote in message
...

So one thinks perhaps I need to end-feed as per:

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|
|
x

back garden


Latest thoughts:

If I could get a decent ground (and that's unknown) I bet I could do a lot
worse than an inverted -L, to use for 40, 80 and 160.

Best I could do:

10m 10m
------------------------------------------------
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| pole on house
| 10m
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x feed

back garden front garden

Yep, might be worth a try if I can get a decent ground.

In article ml50d.17720$aW5.7105@fed1read07,
"Craig Buck" wrote:

With linear loading, you can get up a lot of wire in a small space. Take a
look at
http://hamgate.sunyerie.edu/~larc/su...inverted_v.htm for
an example of a 160 meter inverted vee in a 40 foot yard!

If you want multi band operation, put up as much wire as you can and feed it
with ladder line to a 1:1 balun to a short piece of coax to a tuner.

Feed it at the top so the maximum current is up high.

If an inverted L works for your lot, try feeding it at the top middle
instead of the bottom end and using the linear loading technique to make
each leg longer. According to Cebik if you can get 3/8s wavelength, you are
very close to the full performance of a half wave. Feeding at the top
middle does not require a radial field to work.
--
Radio K4ia
Craig "Buck"
Fredericksburg, VA USA
FISTS 6702 cc 788 Diamond 64
[snip]

Some nice suggestions, there, especially the point about keeping the
maximum current area of the antenna as high as possible.

The antenna can be end-fed (high impedance), off-center fed (moderate
impedance) and center-fed (low impedance). With a good antenna tuner, I
don't s'pose it much matters about impedance, as long as the varying
amounts fall within the tuner's range.

It was a revelation to me to realize that a half-wave length of wire
doesn't really care where it is fed: end, off-center, or mid-point. The
high-current portion will be in the middle and the high-voltage points
will be at the ends, regardless of where the feed point is located, as
long as the wire is resonant at the operating frequency.

Linear loading is effective, but as more wire is tightly folded back
from the ends, the more narrow the 'bandwidth' becomes, limiting the
tuneable range. This would also pretty much kill the multi-band utility
of the antenna.

I use a 130-foot ladderline fed dipole, center-fed. In a location like
yours, I'd keep as much of the center portion of the antenna as high and
level as possible, and then at each far end I'd fold them down and to
the side, and then back along the fence toward to the center as far as
needed, clipping the wire to stand-off insulators and keeping them up
out of reach of curious fingers. The radiation from the end portions is
less, and is a practical compromise for 80 meters and up.

For 160 meter operation, I use "clip on" extensions that run along my
perimeter fence on both sides, and they make a sort of "Z" in respect to
the main antenna. This works very well, letting the center part of the
dipole radiate up high, while providing enough physical wavelength to
allow tuning.

All of this is a compromise, of course, but it's practical and effective.

I suspect that the performance of the "all band" antenna is somewhat
less effective on 20 meters up .. but this is a much more approachable
situation. I've acquired an end-fed trapped half-wave vertical for 20
thru 10 meters that is only 17 feet in length. I plan to mount it on a
mast alongside the house. I suspect that the radiation pattern on 20
meters and up from this "vertical halfwave" will be much more evenly
distributed and predictable than the multi-node variations of the
tuneable dipole. Between the two antennas, one should be pretty well
covered, given the space restrictions.

Gray K7VGW

--
Reply to: allen/at/graybyrd/dot/com

"Those who figure that freedom is maintained by putting a .50 caliber slug
through anyone and everyone who disagrees with their flag-waving, chest-beating
histrionic rants of patriotism will probably live to see the end of their own
freedoms while hiding behind their locked and shuttered doors, sucking the
barrel of their own shotgun." --me

"Graybyrd" wrote
"Craig Buck" wrote:

With linear loading, you can get up a lot of wire in a small space.
Take a
look at
http://hamgate.sunyerie.edu/~larc/su...inverted_v.htm
for
an example of a 160 meter inverted vee in a 40 foot yard!

If you want multi band operation, put up as much wire as you can and
feed it
with ladder line to a 1:1 balun to a short piece of coax to a tuner.

Feed it at the top so the maximum current is up high.

If an inverted L works for your lot, try feeding it at the top middle
instead of the bottom end and using the linear loading technique to make
each leg longer. According to Cebik if you can get 3/8s wavelength, you
are
very close to the full performance of a half wave. Feeding at the top
middle does not require a radial field to work.
--
Radio K4ia
Craig "Buck"
Fredericksburg, VA USA
FISTS 6702 cc 788 Diamond 64
[snip]

Some nice suggestions, there, especially the point about keeping the
maximum current area of the antenna as high as possible.

The antenna can be end-fed (high impedance), off-center fed (moderate
impedance) and center-fed (low impedance). With a good antenna tuner, I
don't s'pose it much matters about impedance, as long as the varying
amounts fall within the tuner's range.

It was a revelation to me to realize that a half-wave length of wire
doesn't really care where it is fed: end, off-center, or mid-point. The
high-current portion will be in the middle and the high-voltage points
will be at the ends, regardless of where the feed point is located, as
long as the wire is resonant at the operating frequency.

Linear loading is effective, but as more wire is tightly folded back
from the ends, the more narrow the 'bandwidth' becomes, limiting the
tuneable range. This would also pretty much kill the multi-band utility
of the antenna.

I use a 130-foot ladderline fed dipole, center-fed. In a location like
yours, I'd keep as much of the center portion of the antenna as high and
level as possible, and then at each far end I'd fold them down and to
the side, and then back along the fence toward to the center as far as
needed, clipping the wire to stand-off insulators and keeping them up
out of reach of curious fingers. The radiation from the end portions is
less, and is a practical compromise for 80 meters and up.

For 160 meter operation, I use "clip on" extensions that run along my
perimeter fence on both sides, and they make a sort of "Z" in respect to
the main antenna. This works very well, letting the center part of the
dipole radiate up high, while providing enough physical wavelength to
allow tuning.

All of this is a compromise, of course, but it's practical and effective.

I suspect that the performance of the "all band" antenna is somewhat
less effective on 20 meters up .. but this is a much more approachable
situation. I've acquired an end-fed trapped half-wave vertical for 20
thru 10 meters that is only 17 feet in length. I plan to mount it on a
mast alongside the house. I suspect that the radiation pattern on 20
meters and up from this "vertical halfwave" will be much more evenly
distributed and predictable than the multi-node variations of the
tuneable dipole. Between the two antennas, one should be pretty well
covered, given the space restrictions.

Gray K7VGW


Many thanks. I do not have the space for this 4th HF antenna to get 1/2
wavelength of 2.182 mhz (214'). I can manage 1/4~ in the fashion of an inv-L
antenna. A big compromise to begin with, but how would that utilize it's
desired 1/4~ electrical length if I fed it anyplace but from the end? I can
add radials and will have to do so if the end-fed inv-L turns out to be the
best by consensus. Earth is sandy with a little clay - not very good. An
MFJ-962D manual or MFJ-994 ATU, whichever performs better, and a 1:1 current
balun at the feedpoint (if helpful) will be used. Estimated height of the
vertical radiator from shield-grounded feedpoint to the "L" would be 37' and
the remaining 70' of radiator would be horizontal. Comments on the expected
efficiency of this arrangement for best performance on 2182-4125 khz are
greatly appreciated. Anyone who is capable of modeling this design, that
would be seriously helpful too ;-)

73,

Jack Painter
Virginia Beach VA

Jack Painter wrote:
... then I thought a 4:1 balun could help make 2182khz tunable on an
antenna with dipole properties that is really too short (would have to be
107' each leg not 107' total, which is about all I can get at that
location).

A "too short" dipole has a feedpoint resistance lower than 50 ohms.
Why would one use a 4:1 balun to attempt to divide that already too
low resistance by 4?
--
73, Cecil http://www.qsl.net/w5dxp


-----= Posted via Newsfeeds.Com, Uncensored Usenet News =-----
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-----== Over 100,000 Newsgroups - 19 Different Servers! =-----

Two big advantages of the center top feed as opposed to bottom end feed is
center top requires no radials. Bottom L will need a minimum of 8 100 foot
radials in your application and some would argue you need many more than 8.
Have fun burying 800+ feet of wire. Second, top feed gets the high current
radiating part of the antenna up higher. Check out
http://www.cebik.com/ltv.html and his discussion of ladder line at
http://www.cebik.com/gup/gup32.html. He concludes a 1:1 balun is best.

If you have 37 feet of height you can feed at the top and run the wire
straight down, back up and then down again for a total of 3x37= 111 feet of
wire on the vertical side. On the horizontal just bend back at the end or
let the end drop down vertically. Sure it will have narrower bandwidth than
a straight dipole but you have a tuner and you can't have a straight dipole.
--
Radio K4ia
Craig "Buck"
Fredericksburg, VA USA
FISTS 6702 cc 788 Diamond 64


"Jack Painter" wrote in message
news:n890d.31528$Ka6.3203@okepread03...

"Graybyrd" wrote
"Craig Buck" wrote:

With linear loading, you can get up a lot of wire in a small space.
Take a
look at
http://hamgate.sunyerie.edu/~larc/su...inverted_v.htm
for
an example of a 160 meter inverted vee in a 40 foot yard!

If you want multi band operation, put up as much wire as you can and
feed it
with ladder line to a 1:1 balun to a short piece of coax to a tuner.

Feed it at the top so the maximum current is up high.

If an inverted L works for your lot, try feeding it at the top middle
instead of the bottom end and using the linear loading technique to
make
each leg longer. According to Cebik if you can get 3/8s wavelength,
you
are
very close to the full performance of a half wave. Feeding at the top
middle does not require a radial field to work.
--
Radio K4ia
Craig "Buck"
Fredericksburg, VA USA
FISTS 6702 cc 788 Diamond 64
[snip]

Some nice suggestions, there, especially the point about keeping the
maximum current area of the antenna as high as possible.

The antenna can be end-fed (high impedance), off-center fed (moderate
impedance) and center-fed (low impedance). With a good antenna tuner, I
don't s'pose it much matters about impedance, as long as the varying
amounts fall within the tuner's range.

It was a revelation to me to realize that a half-wave length of wire
doesn't really care where it is fed: end, off-center, or mid-point. The
high-current portion will be in the middle and the high-voltage points
will be at the ends, regardless of where the feed point is located, as
long as the wire is resonant at the operating frequency.

Linear loading is effective, but as more wire is tightly folded back
from the ends, the more narrow the 'bandwidth' becomes, limiting the
tuneable range. This would also pretty much kill the multi-band utility
of the antenna.

I use a 130-foot ladderline fed dipole, center-fed. In a location like
yours, I'd keep as much of the center portion of the antenna as high and
level as possible, and then at each far end I'd fold them down and to
the side, and then back along the fence toward to the center as far as
needed, clipping the wire to stand-off insulators and keeping them up
out of reach of curious fingers. The radiation from the end portions is
less, and is a practical compromise for 80 meters and up.

For 160 meter operation, I use "clip on" extensions that run along my
perimeter fence on both sides, and they make a sort of "Z" in respect to
the main antenna. This works very well, letting the center part of the
dipole radiate up high, while providing enough physical wavelength to
allow tuning.

All of this is a compromise, of course, but it's practical and effective.

I suspect that the performance of the "all band" antenna is somewhat
less effective on 20 meters up .. but this is a much more approachable
situation. I've acquired an end-fed trapped half-wave vertical for 20
thru 10 meters that is only 17 feet in length. I plan to mount it on a
mast alongside the house. I suspect that the radiation pattern on 20
meters and up from this "vertical halfwave" will be much more evenly
distributed and predictable than the multi-node variations of the
tuneable dipole. Between the two antennas, one should be pretty well
covered, given the space restrictions.

Gray K7VGW


Many thanks. I do not have the space for this 4th HF antenna to get 1/2
wavelength of 2.182 mhz (214'). I can manage 1/4~ in the fashion of an
inv-L
antenna. A big compromise to begin with, but how would that utilize it's
desired 1/4~ electrical length if I fed it anyplace but from the end? I
can
add radials and will have to do so if the end-fed inv-L turns out to be
the
best by consensus. Earth is sandy with a little clay - not very good. An
MFJ-962D manual or MFJ-994 ATU, whichever performs better, and a 1:1
current
balun at the feedpoint (if helpful) will be used. Estimated height of the
vertical radiator from shield-grounded feedpoint to the "L" would be 37'
and
the remaining 70' of radiator would be horizontal. Comments on the
expected
efficiency of this arrangement for best performance on 2182-4125 khz are
greatly appreciated. Anyone who is capable of modeling this design, that
would be seriously helpful too ;-)

73,

Jack Painter
Virginia Beach VA

Richard wrote:
Just wondering: If you had a 33 foot horizontal wire, fed at one end with a
ladder line, which was connected to an atu, it would work on 20 metres, but
would it work on 40, 80 and 160metres? TIA.

On 40m, 80m, and 160m, it would act more like an inverted-L
with lots of feedline radiation. On those bands, you might
as well put up an inverted-L.

On 20m, it would have a very high feedpoint impedance in the
neighborhood of thousands of ohms. The feedpoint current is
pretty low so the current unbalance has a limit. For 100w, the
feedpoint current would be about 0.15a. Of course, the feedpoint
current in the other wire is zero since it is floating at the
antenna feedpoint.

On 40m, it would have a very low feedpoint impedance in the
neighborhood of 40 ohms. For 100w, the feedpoint current
would be about 1.5a, a magnitude more current unbalance
than the 20m case.
--
73, Cecil http://www.qsl.net/w5dxp


-----= Posted via Newsfeeds.Com, Uncensored Usenet News =-----
http://www.newsfeeds.com - The #1 Newsgroup Service in the World!
-----== Over 100,000 Newsgroups - 19 Different Servers! =-----

"Craig Buck" wrote

Two big advantages of the center top feed as opposed to bottom end feed is
center top requires no radials. Bottom L will need a minimum of 8 100
foot
radials in your application and some would argue you need many more than
8.
Have fun burying 800+ feet of wire. Second, top feed gets the high
current
radiating part of the antenna up higher. Check out
http://www.cebik.com/ltv.html and his discussion of ladder line at
http://www.cebik.com/gup/gup32.html. He concludes a 1:1 balun is best.

If you have 37 feet of height you can feed at the top and run the wire
straight down, back up and then down again for a total of 3x37= 111 feet
of
wire on the vertical side. On the horizontal just bend back at the end or
let the end drop down vertically. Sure it will have narrower bandwidth
than
a straight dipole but you have a tuner and you can't have a straight
dipole.
--

Hi Craig, Mr. Cebik says nothing about wrapping radiators back and forth
near each other as the earlier referenced url:
http://hamgate.sunyerie.edu/~larc/su...inverted_v.htm

Cebik does comment:
"Bending the horizontal arm far end down: If horizontal space is limited, a
common practice is to bend (or dangle) the outer ends of a dipole downward.
since the region is the high voltage and low current portion of the antenna,
the radiation pattern is least affected by modifying the geometry." -and-

"Like many wire antennas, the inverted-L will tolerate moderate alterations
of geometry to fit the space available and still yield good, if not peak,
performance."

each leg longer. According to Cebik if you can get 3/8s wavelength,
you
are
very close to the full performance of a half wave. Feeding at the
top
middle does not require a radial field to work.

It doesn't appear that Cebik intended to imply that 3/8~ off-center feed
would ever approach true1/2~ dipole performance, just that it would still
operate. These off-center-fed variations (of Carolina Windhams?) are
confusing, no matter how much wire they use. Remember I don't need an
all-band compromising performer like the T2FD or Windham, but a specific
performer on 2182 Khz, and hopefully at least through 4125 Khz. Doing this
with 70' of horizontal span and two vertical attachment points about 37'
high is the challenge I am asking for help with. I cannot run anything like
KGØZP does, which creates (in his location) a near-field coupling nightmare,
in my opinion. Your suggestion (doubling the verticals), which varies from
both the KGØZP design and Cebik's "moderate geomtery alterations", would at
least add electrical length, but it remains off-center-fed and therefore
never creates a 1/2~ dipole, correct?

If I stuck with a 1/4~ end-fed L, and only used 8 radials of 20-40', could
this still outperform an off-center-fed antenna off any length on 2182 Khz?

Thanks again for the comments and ideas,

Jack painter
Virginia Beach VA

On Fri, 10 Sep 2004 13:39:05 -0400, "Jack Painter"
wrote:

But I need to improve transmit capability to a reliable 200 miles
minimum. And yes, we do get grazed often and ocassionally hit by hurricanes
here. ;-)

Hi Jack,

What options are available to you? Got any towers?

73's
Richard Clark, KB7QHC

"Richard Clark" wrote in message
...
On Fri, 10 Sep 2004 13:39:05 -0400, "Jack Painter"
wrote:

But I need to improve transmit capability to a reliable 200 miles
minimum. And yes, we do get grazed often and ocassionally hit by
hurricanes
here. ;-)

Hi Jack,

What options are available to you? Got any towers?

73's
Richard Clark, KB7QHC

Richard, towers are courtesy of Virginia Loblolly Pine! They run all the way
into the heavens, attract lightning like nobody's business, and pretty much
ruin homes when they come down in hurricanes or Nor'Easter's. But they are
also god-given antenna towers offering large limbs starting at about 50' on
up. I try to use the lower parts of the trees (50') so as to reduce sway.
From a 3' dia tree there is none, the more slender sky-cranes move a lot.

| |
-0- ------------------------------------0-
| |


-- --
| |
^ |----- / /------|
| | |
50' | |
| |
| |
------------ 70' ----------------

Basically, I have similar arrangements for 5 & 8mhz dipole, longwire, random
wire, etc.

Jack

Hi Jack,

I usually lurk here quietly, but thought
I'd stick my neck out.

I just did a quick analysis on EZNEC.
Imagine a wire that is 50 feet up, 70
feet across the top, hanging down 40
feet on each end for a total of 150 feet.
Feed it in the center of the top with
75 feet of 450 ohm line.

The impedance seen at the end of 75
feet of 450 ohm feedline looked pretty
workable on both 2182 and 4125 kHz.
(Yes, you need an antenna tuner, but
it could be very simple for just two
frequencies.) An NVIS antenna like
this is great for short range (a few
hundred miles).

Download the demo version of EZNEC
from www.eznec.com . It'll take you a
couple of hours to get familiar with it,
but then you can play "what if" with
a lot of simple antennas like this.

73, John - K6QQ