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1-10 of 22 messages
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End Fed - HF multi-band - What's the real story?
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by KC8TMV on April 29, 2009
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I have drawn out about every dipole type antenna I can think of to fit my back yard. It is long and narrow, and the very best "fit", as far as space is concerned, is an end fed antenna. Physically it is a prefect fit, but, like most of us, I want to get everything I can get out of an antenna.
It would be great to be able to work 10-80 (160 would be a plus) with just this one antenna. I have a TS-450S, so a tuner is built in.
I have not read enough "positive" results of an end fed antenna to prove to me that this is the right way to go. If I do a center fed, or off center, I would have to reduce the length, due to the land, building location, etc. So that is why I am think of the end-fed.
Would you guys be kind enough to 1, give me your two cents, and 2, suggest a good design (i.e. feed wire, baluns, etc.)?
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RE: End Fed - HF multi-band - What's the real story?
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by W5GA on April 29, 2009
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With just the built in tuner, you won't be happy with the results. To make this play on all bands, you'll require an outboard tuner with a really wide matching range.
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RE: End Fed - HF multi-band - What's the real story?
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by AA4PB on April 29, 2009
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The internal tuner is not likely to be able to match an end-fed antenna. In addition, an end-fed antenna MUST ALWAYS have a counterpoise (such as burried radials) to work against. The best way to do an end-fed antenna is to place an SGC automatic tuner on the ground. Bury a number of radials and connect them to the ground terminal on the tuner. Connect the antenna to the antenna terminal and set it up as an inverted-L configuration.
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RE: End Fed - HF multi-band - What's the real story?
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by W0SZP on April 29, 2009
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I agree with the fellas, especially with regard to the auto tuner not up to the task. I owned a TS-450S for many years and it will tune up easily for something that's close but to ask it to tune an end fed will most likely break the auto tuner and kill your resale value. An inverted L sounds like a worthy candidate for your QTH but you're gonna need a heavier duty tuner to make it work. Best of luck and have fun!
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RE: End Fed - HF multi-band - What's the real stor
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by WB6BYU on April 29, 2009
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First of all, the tuner in your TS-450 doesn't work on
160m (at least if it is like mine.) And while the tuner
does a pretty good job of matching reasonably high SWR on
coax lines, the impedances typically encountered with an
end-fed antenna likely will be out of the range that it
can handle by itself. Not that there aren't several ways
around this, just that they take a bit more work.
I've used a number of end-fed wires over the years, often
with non-optimum feed systems. Yes, they can work fairly
well, and it helps to have a good understanding of the
issues involved.
First, any end-fed antenna needs to be fed against SOMETHING.
Ideally this would be a set of radials or a good ground
plane for the bands to be used. This is not always convenient
when the antenna is in the air, but I've had good results
using metal window frames as a ground when all the ones
in a building are bonded together.
(One could present the Zepp feed as a counterexample,
but a careful observation of the currents on the wires
shows that usual simplistic analysis really doesn't tell
the whole story about how it works. While this can be
made to work acceptably well on some bands, the actual
behavior probably is closer to an inverted L.)
This is why the inverted L (horizontal wire plus short vertical
wire, fed at ground level) is probably a good choice:
it can be fed against ground radials and gives a combination
of horizontal and vertical polarization. If the total
wire length is around 100 to 150' it can be tuned with
a series capacitor or inductor for a reasonably low SWR.
On the higher bands, however, the impedance (with just
about any wire length, actually) will vary a lot with
frequency. Actually it isn't the impedance at the
antenna that your tuner has to handle, it is the impedance
at the end of the coax, and that can be even worse. The
best approach that I have found is to use some type of
matching system at the base of the antenna. This can be
an auto-tuner, or just a manually-switched network that
uses the auto-tuner in the rig for fine adjustment.
The design of this network will depend on the exact wire
length. Actually I like the manual approach as I can
optimize the match for the actual impedance on each band.
Start with one or two bands of particular interest and
get them working, then you can operate on those while
you experiment with adding more bands to the tuner. You
may find that some of the networks allow you to use
multiple bands, saving you some work.
The radiation patterns will also vary from band to band,
and may not always be optimum for the desired communications.
But having ANY antenna up, even if it may not be optimum
for some paths, is still better than none at all, and it
will get you on the air.
There are some other options that will allow you to
operate on at least some bands with an elevated feedpoint.
I've used Zepp feed on 80 / 40 / 20 / 15 / 10m, for
example, but the same wire length may not work
as well on 60 or 17m. And even with that the impedances
expected are probably out of the range that the TS-450
tuner can handle. For just one or two bands it shouldn't
be difficult to come up with something, but trying to
cover all HF (and MF) bands does make it more difficult.
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RE: End Fed - HF multi-band - What's the real stor
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by KC8TMV on April 30, 2009
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Thanks for all of the advice guys. It is great to be able to have those of you that have "been there, done that", or simply are a lot smarter than me, assist us newer guys trying to get it right.
I know the internal tuner is only "so" good, and Dayton Hamfest is right around the corner and only about 30 minutes from the QTH! So a tuner is going to be on the list to look for.
After your feedback, a little more research, and a little compromise on what I will accept visualy in my backyard, I am turing my thoughts to a Windom dipole. This will keep the one leg shorter (where I have the physical restrictions) and allow me to keep the other leg longer where I don't have the physical restrictions.
Is there anything special I need to know about this type of antenna? Grounding, radials, etc?
Again, thanks in advance for your advise!
-Steve
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RE: End Fed - HF multi-band - What's the real stor
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by K8AC on April 30, 2009
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As teenagers a long time ago, all the guys in our club used end-fed random wires with pretty good success. We didn't know about the need for a counterpoise of some sort, so it was common for everything to be hot with RF, even with only 25 watts output. The wire was simply run into the room under the window sash and connected to the tuner which sat on top of the transmitter. The advice of using an SGC or similar tuner OUTDOORS with a ground system is very good advice. I used that arrangement as late as 8-9 years ago with great success, using just a single 130 foot wire as a counterpoise. The original Windom antenna was single-wire fed and not considered a "dipole". It worked very well as a multi-band antenna, again requiring a good ground system.
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RE: End Fed - HF multi-band - What's the real stor
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by WB6BYU on April 30, 2009
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A traditional "Windom" has a single wire feed, which you
would handle just like the end-fed long wire. The "dipole"
version is often called an OCFD (Off-Center Fed Dipole)
and there are a number of commercial versions, or you can
make your own. With some of the commercial versions
your internal tuner may be adequate to tune it on most of
the bands that it is designed for.
They certainly aren't perfect, and may not live up to some
of the advertising claims made about them, but if it fits
your space it isn't a bad option.
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RE: End Fed - HF multi-band - What's the real stor
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by WA8MEA on May 1, 2009
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I've got a 160 meter dipole in my small yard.
I've got all types of bends in the wire elements from 90 degree angles to 45 degree angles....just to make it fit. I have a pretty darn good match centered at about 1875 kHz (1.2 to 1) and as high as 1.9 to 1 at the edges of 1850 kHz to 1915 kHz.
73, Bill - WA8MEA
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RE: End Fed - HF multi-band - What's the real story?
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by KG6AF on May 1, 2009
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I've had good luck with a Par end-fed antenna on 20 meters; if the reviews are any indication, lots of other amateurs have had success, too:
http://www.eham.net/reviews/detail/3632
Par also makes a three-band QRP version (I have one, but haven't used it yet):
http://www.eham.net/reviews/detail/5105
Each of these antennas comes with a small matching network at the antenna feedpoint. While I don't know what the internals look like, it's a fair guess that there's a low-to-high-Z transformer, and that some counterpoise current is injected into the outside of the coax shield. In some installations this may be a problem, although the reviews seem to indicate that few, if any, owners are having difficulty with this.
I have no interest in Par except as a very happy user of their 20-meter end-fed.
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