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Author Topic: End fed HF antennas?  (Read 3691 times)
2E0ILY
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Posts: 131




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« on: April 08, 2012, 02:46:06 PM »

I am wanting to replace my random piece of long wire antenna for something  more efficient that I can safely expect to load up for transmission from my old boat anchor Yaesu FT-902DM. The restriction is that it has to be end fed as it goes across our front lawn and I don't want to to be either visually intrusive, nor needing a cable other than the feed in cable running across the place. I have done a very crude sketch of my two obvious anchorage options. My "shack" is the upstairs of our bungalow, and the antenna feed in needs to be via the porthole window it has, at the end of the house. The current long wire has its anchorage above this window, on a rope with two insulators, that exits the brickwork above the window at a height of about 23 feet. The other end of my random wire has another rope anchorage with two insulators at the top of a tree in the garden, at a height of about 30 feet. The length of the wire itself. less guy ropes, is about 190 feet. There's another handy tree in the garden about 100 feet from the house end anchorage, shown on the drawing. I can use that as a second anchorage, or instead of using the tree about 200 feet away. Can anyone think of any half decent options using these 3 fixed points for an HF aerial for 160, 80, 40 and maybe 20 metre bands?  The drawing can be accessed at http://www.gatesgarth.com/plan.jpg  I can run a ground from the garden beneath the level of my shack. The ground wire will terminate in a six foot galvanised earth spike driven into damp soil, it will by necessity be at a distance of about 25 feet from the transceiver and ATU. I know it's not ideal but I have to work within these criteria. Thanks.
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Best regards, Chris Wilson.
W9KDX
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Posts: 770




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« Reply #1 on: April 08, 2012, 04:56:16 PM »

This

http://www.dxzone.com/catalog/Antennas/End-Fed/

would be a good place to start.  I would be concerned that you are not high enough above the ground for 80 and 160 meters, barely enough for 40 m.  The next thing that come to mind is that you have an ideal set up for some sort of off-center-fed dipole.

I have one of these http://www.freewebs.com/hypower/ocf80.html and, while mine is a regular horizontal configuration, it just might work as a horizontal V.  You can email the builder and he will tell you his opinion.  He has been a goor resource for me as I worked mine.

After a height problem, I have heard that the end fed antennas are quite a bit noisier than other dipoles.

« Last Edit: April 09, 2012, 04:41:44 AM by W9KDX » Logged

Sam
W9KDX
KB4QAA
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Posts: 2407




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« Reply #2 on: April 08, 2012, 06:02:20 PM »

If you want to improve your performance you can do two things:


-Add ground counterpoises
-Higher
-Longer

You will find urban ham myths on the internet about specific lengths of wire for multiband ops which are generally buschwa.  Being non-resonant, the only limiting factor is your tuner's ability to load. 

Since you already have a wire up, adding counterpoises (the other half of the antenna) would yield the most immediate improvement. 

If you wanted to operate on One band, an End Fed Zep would be more efficient and have some gain.
« Last Edit: April 08, 2012, 06:05:25 PM by KB4QAA » Logged
KB3TXH
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Posts: 44




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« Reply #3 on: April 09, 2012, 09:45:55 AM »

My end fed zepp, that is 1/2 wave on 80 meters, with about 30 feet of 450 ohm parallel feeder, works well on 80, and 40.
I doubt that it would work well on 160, but I am sure it would load up on 20,15,and 10, with the right feeder length.

Plus rfi is no longer a problem, like it was with a long wire.

I use a 5BTV for the higher freqs.
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2E0ILY
Member

Posts: 131




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« Reply #4 on: April 11, 2012, 02:07:38 PM »

Thanks for the further replies. I fired up my boat anchor Yaesu FT-902DM on transmit into a dummy load last night, with the intention of carefully setting the load, plate and preselect etcetera, to make my first CQ call ever. the excitement was immense. My disappointment was similarly strong when I failed to get anything like a sensible SWR, even with my FC-902 ATU. This has made me determined to do something sooner rather than later. A new licence to transmit and an immediate antenna issue is frustrating, to say the least. i can't even fire up my el cheapo 2 metre FM rig as the chimney lashing kit didn't give enough offset to miss the fancy brickwork the builder saw fit to adorn the chimney top edge with....First job at the weekend is to alter it and weld one some extensions to clear the fancywork. Then I can throw my home made J pole up Smiley
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Best regards, Chris Wilson.
WB6BYU
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Posts: 13336




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« Reply #5 on: April 11, 2012, 05:08:45 PM »

Try a full wave loop of wire for 80m, which would be about 90' on a side.
(Might need some adjustment, but aim for resonance near the bottom of
80m to hit the other bands.)

Feed two wires out through the window, one to each end of the loop.
Depending on the angle between the two trees, you might have to
lengthen the wires from the house and shorten the cross wire to be
able to pull up the slack.  (You can install it a few feet off the ground
for testing the fit.)   Once you get the dimensions set, raise it up
into place.  You can splice the two wires onto a short piece of coax
to connect to the tuner, or connect them directly.

Should tune up much better than an end-fed antenna, and it doesn't
require an RF ground for good performance.

You end up with, essentially, one wire out to each tree and one cross
wire connecting the short tree with the middle of the other wire.
Shouldn't be that much more obvious than the original wire.  I use light
wire and tie synthetic twine directly to it without worrying about discrete
insulators.
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N6XJP
Member

Posts: 9




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« Reply #6 on: April 11, 2012, 06:35:20 PM »

Basil....

I have had extreme good luck with LnR EndFed antennas.   I have three and use them portable in the mountains.  You can tune them by trimming befor leaving home, and them just throw it over a tree.  Works for me with 1:1 swr on the CW freqs I work QRP.  Granted , they are commercially produced, but they work.  My favorite is the 10-20-40 meter antenna... One antenna for three bands.  You can use a short counterpoise if necessary, but I have found it to be unnecessary.  So versatile are they that I use one for my QTH as well...it hangs out of the upstairs window, is tuned for 7.050, and gives me 1:1 SWR for 7.010 to 7.060... 

Love them... And no, I am not connected to the company in ANY way.

Cheers, 

Dave
N6XJP
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