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Author Topic: 75/80meter end fed  (Read 912 times)
KC2RGU
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Posts: 37




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« on: December 04, 2007, 07:56:20 AM »

Currently I'm using a ground mounted hustler 6btv.  I'd like to get better performance on 75meters and maybe even add 160m to my band usage.  The house I live in is built on an old farm field and mature trees to hang a wire in is almost nil.  What I have is an high tension tower about 200' back but I'm sure PSE&G would take issue if I hung a wire from that.  The is a semi big tree about 300' back which would make a wire run almost true north and south.  My idea is to put up a 40' mast on the house and run a wire from that to the tree an build an end fed antenna. That would put the wire up about 60' on one end and about45' on the other end minus the sag in the middle.

??'s are:
Is this antenna high enough to work on 75 and 160m?

What would I use for the counterpoise?  I have a tuner that I can run the counterpoise from.
 
Do you know of any good example of constructing an antenna like this on the web?

What else should I be aware of with this kind of antenna?
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WB2WIK
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Posts: 20595




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« Reply #1 on: December 04, 2007, 09:25:01 AM »

Why not center-feed it?  If you can get it that high above ground, a transmission line hanging from the center of a doublet, especially if it were lightweight like 450 Ohm window line, would not cause any additional sag and would make feeding the antenna much easier, with no special grounding considerations.

End-fed wires are for those with absolutely no other options, but it sounds like you have one.

WB2WIK/6
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WW5AA
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Posts: 2086




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« Reply #2 on: December 04, 2007, 09:40:49 AM »

In your case (simular to my 5BTV), I would remove the stinger from the coil and add a wire or better yet, a run of coax to that tree. A 90' coax flat top added 160 meters and a big improvement on 80/75 for me. Now if I only had room for the four square (:-)

73, de Lindy
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KC2RGU
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Posts: 37




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« Reply #3 on: December 04, 2007, 10:36:31 AM »

The reason I wouldn't center feed a flat top is because the one end of the dipole is the same end of the house where the shack is.  I only have one remote end to hang a dipole.  The shack is the other end.

I'm interested in the concept of removing the stinger (is that the coil?) from the top of the BTV.  Do you have any information on what is involved with this?
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N3BIF
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« Reply #4 on: December 04, 2007, 12:46:29 PM »

...."remove the stinger from the coil"...


 he means remove the whip part from the coil.
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N3BIF
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Posts: 1190




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« Reply #5 on: December 04, 2007, 12:51:38 PM »

..."Why not center-feed it?"


Put up your end fed as you suggested and find its mid point . Cut it in there and feed it  with 450 balanced line. This way you avoid all the problems associated with unbalanced antennas in general, and end feds in particular.
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K0XU
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Posts: 294




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« Reply #6 on: December 04, 2007, 05:31:02 PM »

How about feeding it about 66 feet from the house end (Mast on other side of house?) with 450 ohm window line. That would be one to model. I think I will look at that when I get home. It would probably depend on exactly how much wire is on the long end.

Jim
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ONAIR
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Posts: 1741




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« Reply #7 on: December 04, 2007, 06:27:40 PM »

   How about an end fed bazooka coaxial?  Get yourself a big roll of cable, and a really sharp knife! Smiley
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WB2WIK
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« Reply #8 on: December 04, 2007, 06:40:22 PM »

>RE: 75/80meter end fed  Reply  
by KC2RGU on December 4, 2007  Mail this to a friend!  
The reason I wouldn't center feed a flat top is because the one end of the dipole is the same end of the house where the shack is. I only have one remote end to hang a dipole. The shack is the other end.<

::I understand what you mean, but this is precisely the situation most of us have and we don't resort to end-feeding the antenna.

There are *many* alternatives, including center fed with ladder line dropping straight down to the ground and then routing to the shack; ladder line pulled sideways from the center feedpoint back to a different point on the house, supporting it there and then routing it to the shack; ladderline run at a right angle to the doublet to any convenient point (including another tree in the yard somewhere), to a "remote balun" and then transitioning to coaxial cable which can be then buried and brought to the shack underground; and a dozen other examples.

I wouldn't use an "end fed wire" antenna unless...well, I can't even think of a case where I'd use one.  They're a lot of "trouble" with regard to RF in the shack (RFI ingress/egress), matching, need for good grounding systems, etc.

Center fed is much less trouble overall, even if it takes a few extra hours to engineer the solution.

WB2WIK/6
 
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K6PCW
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Posts: 11




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« Reply #9 on: December 06, 2007, 10:13:40 AM »

Check this set up out:
http://www.n2ckh.com/antfarm.htm

I duplicated Steve's NVIS random wire end-fed setup and I'm having great results on 75 meters (and 160, and 60, 40, and to a certain extent, 20 and 17).

I'm running 240 feet dog-legged from a 6 ft high wooden fence, up 30' feet in a nearby palm tree, across my backyard to another fence, and along that fence for another 100 feet or so.

I'm using the same 9:1 CWS Bytemark balun that he recommends, 8' ground rod, RG-6 coax into the house, an LDG Z100 tuner, and my Icom 718.

Try different lengths of random wire to see what works best for you.  Don't discount the end-fed if that's what you want to do.  It does work satisfactorily, although it is indeed a compromise.  But if that's what will get you on the air, go for it!  

My other end fed (currently) is a Par End-Fedz 75 meter antenna that is running horizontally along the top of the same wooden fence, about 5 1/2 feet off the ground.  The neighbors don't see it, but the darned thing works.  From my place in California, I was listening to some guys in Georgia and Florida on their sked the other night.  Although I use it for more localized nets here on the west coast, that's not bad reception, huh?

Last Spring, using my Par End-Fedz 20 meter antenna sloped upward from the backyard patio to a tree about 12' up, I contacted Norfolk Island (east of Australia) and Fairbanks, Alaska.

Keep experimenting.  Make your own antennas, try different configurations.  That's the challenge!

73
Pete K6PCW
Southern California
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K6PCW
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Posts: 11




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« Reply #10 on: December 06, 2007, 10:16:00 AM »

CORRECTION:
Towards the end of my last post, I mentioned a Par 75 meter on my fence.  That should read Par 40 meter, not 75 (he doesn't make one of those - yet.).
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KC2RGU
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Posts: 37




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« Reply #11 on: December 16, 2007, 07:44:09 AM »

Thanks for all of your suggestions.  I is a big help.  What I think I'm going to do is to put up 2 40' guyed poles and hang a 160m doublet between them.  I have two more questions that I'm hoping you guys could answer.

Is 40' high enough to do any kind of work on 160m?  Or should I stick to an 80m doublet?

Between the house and the proposed location for the doublet is a ground mounted vertical.  How close cat I run the twin lead to the vertical without making a major impact on either antenna?
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K7KBN
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Posts: 2802




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« Reply #12 on: December 16, 2007, 02:32:37 PM »

Sort of depends on what you mean by "work".  40 feet is marginal for 40 meters, where a half wavelength is closer to 66 feet.  It's worse, of course, for 80/75 meters, and not too good at all for 160.  

It is, however, almost infinitely better than NO antenna.  Don't look for much in the way of DX on 80/160, though.
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73
Pat K7KBN
CWO4 USNR Ret.
K8KAS
Member

Posts: 569




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« Reply #13 on: December 17, 2007, 11:19:14 AM »

A friend of mine (WD8QKE) uses a 5BTV with a 40 meter trap installed at the top, and then a 23 foot wire. This also could be used on 160 if you added a 75/80 meter trap at the end of the 23 foot wire. With any current fed 1/4 wave you need a good RF ground. He uses 30 or so 50 foot radials plus a chain link fence. He works anything he can hear and is always one of the loud stations in our group. You can't ask for a simpler antenna. PS, 160 meter dipoles@40 foot are cloud warmers, a good Inverted L (like the 5BTV and top wire would blow them away, thats with a good RF ground. I don't know why its so hard to get hams to understand how important the ground is, Marconi understood this 70 years ago and hams today still question a good ground, Duh.
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