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Author Topic: My New Antenna Situation.  (Read 22678 times)

gil

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My New Antenna Situation.
« on: May 07, 2016, 02:01:12 PM »
Hello :)

I have a challenge being in need of a temporary new antenna... The situation is simple, a two story house and a pine tree in the backyard about 90 feet away. The wire would go from the top of the pine tree to the top corner of the house. I am thinking of something like a W3EDP (http://www.nc4fb.org/wordpress/w3edp-multi-band-antenna/). The wire would be 84ft. My issue is that I will not have access to the feed point to either change counterpoises or tune a variable capacitor.

I'll attach a photo... The tree is taller than it looks, so the wire should be close to horizontal.

So, I need to find out how to feed it, and maybe attach two counterpoises of 6.5 and 17ft at 45 degrees on the side of the house... I must use coax from the top of the house to the inside... Maybe the EARCHI (http://earchi.org/92011endfedfiles/Endfed6_40.pdf) end-fed tuner would work...

BTW the wire orientation is at about 300deg, feed point on the North side. Height looks like 20ft, maybe a few feet more at the feed point.

I hope to use it on 20/30/40/80m. Other bands later if I can...

Any suggestions about feeding?

Gil.
« Last Edit: May 07, 2016, 02:30:58 PM by gil »

cockpitbob

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Re: My New Antenna Situation.
« Reply #1 on: May 08, 2016, 12:24:39 AM »
Here's an 8-band resonant end-fed]Here's an 8-band resonant end-fed. 
http://myantennas.com/wp/product/efhw-8010/
No tuner or capacitor to adjust.  Plug and play with the feed point at the end of 130' of wire.  If I ever fix my house's noise problem (S8 to S9), I'm getting this.  They say 1KW but reports I read suggest the transformer cores start to saturate at 300W.  Still, a great 100W antenna.

gil

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Re: My New Antenna Situation.
« Reply #2 on: May 11, 2016, 08:58:15 AM »
I thought about that one Bob, and might yet get it. I could string up a 256ft wire, one end at around 20ft and the other at six feet off the ground.. That's getting close to a half wave on 160m! Question is... Would I want to? The 80-10 might be just the easy way...

Gil

Lamewolf

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Re: My New Antenna Situation.
« Reply #3 on: May 17, 2016, 05:11:53 PM »
So, I need to find out how to feed it, and maybe attach two counterpoises of 6.5 and 17ft at 45 degrees on the side of the house... I must use coax from the top of the house to the inside... Maybe the EARCHI (http://earchi.org/92011endfedfiles/Endfed6_40.pdf) end-fed tuner would work... <snip>

Just for your information, the "EARCHI" is not a tuner, its nothing more than a 9:1 unun feeding an end fed wire and the unun is fed with coax leading to the shack and a tuner in the shack to provide the match.  While it will work, there will almost never be a good match without a tuner except for maybe a few rare frequencies.  The idea behind it is to just keep the swr within a range that most auto tuners can handle it, but its not an optimum setup by a long shot.

I have a similar setup. I have an 88' sloper but my feedpoint is at 7' with a 4:1 unun that also has a 1:1 choke behind it to keep RF off the coax shield and the far end at 70'.  The ground side of the unun is actually connected through a ground wire going to my ground rods and I get great signal reports on 40 through 160 meters with it (using a tuner in the shack to provide the match).  It currently has no counterpoise wires at all - just the ground connection.  I mainly put it up to use as an end fed half wave for 60 meters and had a mactching circuit on it for that band but wanted to work 160 with it too, so I replaced that with the 4:1/1:1 combo.
« Last Edit: May 17, 2016, 05:23:26 PM by Lamewolf »

gil

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Re: My New Antenna Situation.
« Reply #4 on: May 20, 2016, 06:23:16 AM »
Yep, I know the EARCHI is a 9:1 UNUN. I emailed the designer of the antenna and he told me 60ft was the absolute maximum wire length, though I have seen posts from people using up to a 66ft wire successfully. A 71ft "random" length would be ideal to include 80m operations. I will try some time just out of curiosity. I have ordered five T130-2 toroids to make one.

I also figured I could use one of those T130-2 to make a 4:1 BALUN for a Windom half wave on 80m with one side being 44ft and the other one 89ft. The wire from SotaBeams is too thin to support itself on such a horizontal length so I bought 50m of polypropylene clothe-line. It's a bit stretchy so I will have to account for that. Build photos upcoming..

Half of the long side will be sloping down. I hope it won't affect SWR too much. The antenna should be resonant on 80, 40, 20, 17, 12, 10 and 6m, 15 and 30m with a tuner.

http://www.hamradioqrp.com/2015/11/the-amazing-80m-multi-band-windom.html

Gil.

Lamewolf

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Re: My New Antenna Situation.
« Reply #5 on: May 26, 2016, 04:08:30 PM »
Yep, I know the EARCHI is a 9:1 UNUN. I emailed the designer of the antenna and he told me 60ft was the absolute maximum wire length, though I have seen posts from people using up to a 66ft wire successfully. A 71ft "random" length would be ideal to include 80m operations. I will try some time just out of curiosity. I have ordered five T130-2 toroids to make one.

I also figured I could use one of those T130-2 to make a 4:1 BALUN for a Windom half wave on 80m with one side being 44ft and the other one 89ft. The wire from SotaBeams is too thin to support itself on such a horizontal length so I bought 50m of polypropylene clothe-line. It's a bit stretchy so I will have to account for that. Build photos upcoming..

Half of the long side will be sloping down. I hope it won't affect SWR too much. The antenna should be resonant on 80, 40, 20, 17, 12, 10 and 6m, 15 and 30m with a tuner.

http://www.hamradioqrp.com/2015/11/the-amazing-80m-multi-band-windom.html

Gil.

I would not use the mix 2 core for a balun feeding an off center fed dipole - little to no choking effect with a powdred iron core which equates to enormous common mode currents getting back to the shack on the coax shield.  Better to use something like the ferrite cores like the FT140-43 or FT140-61 cores wound in a dual core current balun.  If you do use the T130-2 for the 4:1, then put a 1:1 choke right under it in the same enclosure to choke off the CMC.  Build the choke with 18 turns bifilar insulated wire on an FT140-43 - that's about 6000 to 8000 ohms @ 3.5mhz of choking impedance.  But you would be much better off using the dual core 4:1 Guanella balun wound on the ferrite cores to begin with.

BTW:  I have used wires up to 124 feet successfully with a 9:1 balun, but I wind my 9:1 balun on FT240-61 cores.
« Last Edit: May 26, 2016, 04:10:10 PM by Lamewolf »

gil

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Re: My New Antenna Situation.
« Reply #6 on: May 27, 2016, 11:46:41 AM »
Quote
Better to use something like the ferrite cores like the FT140-43

Darn, I'm going to gave to wait! Thanks for the info though! The T130-2s aren't here yet.. Those are for the 9:1 ununs.

Now I need to go on Ebay and get a FT140-43. Would it be better for the 9:1 EARCHI unun as well?

I found a schematic for an end-fed transformer on Ebay too...

Gil.

Lamewolf

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Re: My New Antenna Situation.
« Reply #7 on: May 27, 2016, 01:07:29 PM »
Quote
Better to use something like the ferrite cores like the FT140-43

Darn, I'm going to gave to wait! Thanks for the info though! The T130-2s aren't here yet.. Those are for the 9:1 ununs.

Now I need to go on Ebay and get a FT140-43. Would it be better for the 9:1 EARCHI unun as well?

I found a schematic for an end-fed transformer on Ebay too...

Gil.
 

I've made a lot of baluns and ununs, and for flatter bandwidth I prefer the mix 61 cores for winding baluns and ununs, and mix 43 more for 1:1 chokes.  The mix 61 cores work well for 9:1 ununs and have a flatter bandwidth than the mix 2 powdered iron and use less turns than the mix 2.  The mix 2 take about 18 turns while the 61's take about 12 turns for 10 thru 80 meters.  If you want a super good setup for an off center fed dipole, get 2 FT140-61 cores and wind them with 12 bifilar turns each in a 4:1 Guanella balun and then feed that with a 1:1 choke that is wound with 18 turns bifilar on an FT140-43.  Actually, you can add the choke to any balun or unun if you want to keep RF off the coax shield but when feeding an end fed wire, use a good ground or counterpoise with it too.  The mix 2 powdered iron cores will work also, but all they basically do is give an impedance transformation but without much choking effect at all.

KC8AON

gil

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Re: My New Antenna Situation.
« Reply #8 on: May 27, 2016, 07:24:21 PM »
Thanks Richard. I was going to make a one core Guanella balun.. I can use two cores? Is that better? So, adding the choke would make a three-core system? My only concern then would be the weight on the wire, since I have no central support.. Maybe I could use smaller cores since the power would never exceed 30W. Enlight me please, I have never looked into balun until now..

Gil

Lamewolf

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Re: My New Antenna Situation.
« Reply #9 on: May 31, 2016, 08:04:04 AM »
Thanks Richard. I was going to make a one core Guanella balun.. I can use two cores? Is that better? So, adding the choke would make a three-core system? My only concern then would be the weight on the wire, since I have no central support.. Maybe I could use smaller cores since the power would never exceed 30W. Enlight me please, I have never looked into balun until now..

Gil

A 2 core guanella current balun is the only "true" guanella balun and far exceeds the performance of a single core.  A single core is alright for something like a loop but works pretty poorly on a Windom type antenna.  And yes, you can use smaller cores like the FT114-61 and FT114-43 to save weight.  Feed it with the tiny RG316 coax to save even more weight.  Take a look at the Arial 51 antenna at this site to get a better idea: http://www.aerial-51.com/model-404-ul/

KC8AON

gil

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Re: My New Antenna Situation.
« Reply #10 on: May 31, 2016, 08:48:56 AM »
Thanks. I ordered the FT-140-61 cores.. I just have to wait now...

Gil.

Lamewolf

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Re: My New Antenna Situation.
« Reply #11 on: June 08, 2016, 07:51:12 AM »
Thanks. I ordered the FT-140-61 cores.. I just have to wait now...

Gil.

Those will handle about 400 watts !

gil

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Re: My New Antenna Situation.
« Reply #12 on: June 09, 2016, 03:58:28 AM »
Got'em! I guess I'll be making a balun soon :-)

Gil

Lamewolf

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Re: My New Antenna Situation.
« Reply #13 on: June 10, 2016, 04:07:26 PM »
Got'em! I guess I'll be making a balun soon :-)

Gil

Here is a link to some good instructions: http://www.korpi.biz/balun%201%20to%204%20dual.pdf

cockpitbob

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Re: My New Antenna Situation.
« Reply #14 on: June 10, 2016, 06:41:51 PM »
Elecraft sells balun kits, but you can clone their design.  They are simple.  As usual, all you need is a core and wire.

The BL1 is either a 1:1 or 4:1 depending on how it's wired.  You can put a switch on it.  It is wound on a binocular core instead of 2 toroids.  The core is an Amidon BN-43-7051.  They claim 150W but I have my doubts.  I personally wouldn't use it at or below 3.5MHz with 100W with FM or digital modes(might get warm).  100W CW at 3.5MHz and above would be OK so long as you don't put a brick on the key.

Look on elecraft's manuals page for the BL1 in 1:1 and 4:1:  http://www.elecraft.com/K2_Manual_Download_Page.htm

I'm kind of surprised they didn't put a switch on the board, but they did with the 250W (uses 2 binocular cores) BL2.  It can be switched between 1:1 and 4:1. 8)






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Re: My New Antenna Situation.
« Reply #14 on: June 10, 2016, 06:41:51 PM »