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Author Topic: Delta loop antenna - may I turn the antenna upside down?  (Read 2813 times)
LZ1MAK
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Posts: 5




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« on: January 09, 2012, 12:57:54 AM »

I already made a delta loop antenna and the antenna is still inside the room. The antenna is feed 1/4 wave from the top (option 1, see the picture). It is possible to turn the antenna with the horizontal part at the top (option 2)?
I don't understand everything about the feed. Do I have to change the feed point or everything is ok at the current way?
please see option 1 and option 2:

http://prikachi.com/images/501/4242501c.jpg

What do you think: will option 2 work?
 /Sorry about my poor English/
Thank you
LZ1MAK/KC2YZL
Marin Kusev
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VE7SQ
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Posts: 6




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« Reply #1 on: January 09, 2012, 01:29:22 AM »

Hi Marin

I have been experimenting with Delta loop antennas since 1975, it is an excellent antenna. My 1st antenna was a 2 element phased 80 meter DL array up 120 feet. I found that you can feed a single element just about anywhere. The Z is mostly 120 --- 140 ohms on 80 meters at 1/2 wavelength to the top. I feed a single element with a 1:1 balun, then an electrical 1/4 wavelength of 75 ohm from the balun. Connect a 50 ohm coax to the 75 ohm coax to the shack. The SWR will be less then 1.5:1. I usually feed my delta loops at the apex. There has been instances where you can feed the antenna at either corner. You will experience a lobe shift in one direction and the radiation angle will change as the feed is more vertical.

73 Bob VE7SQ

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LZ1MAK
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« Reply #2 on: January 09, 2012, 02:16:09 AM »

Thank you very much Bob,
Yes I did the same - feed the antenna with 1/4 wave 75 OM coax and than with 50 OM coax. I hope there is enough place at the roof for the delta loop, till this time I used only dipole antennas, so I want to try something else. Wish you everything the best for you and your family, many DX-es
73 Marin
LZ1MAK
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WX7G
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« Reply #3 on: January 09, 2012, 05:41:15 AM »

To retain predominantly vertical polarization with a symmetrical azimuth pattern feed it as shown in your diagrams. Not at the apex, not at a corner, and not at the center of the horizontal wire.
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WB6BYU
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« Reply #4 on: January 09, 2012, 06:49:02 AM »

Yes, you can.  There will be a slight increase in the effective height above ground,
but probably little observable difference in performance.
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K7ZRZ
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Posts: 279




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« Reply #5 on: January 09, 2012, 04:32:38 PM »

Marin,

You said you put it together indoors.  Does that mean that it's a 6 meter DL or perhaps 10 meters?

I built a 6 meter DL out of 1/4" aluminum rod and am feeding it in the same manner as you have shown.  I ground flat spots at the ends of the rods and drilled small holes for bolts/nuts for assembly/dissassembly. (That works great). I used a piece of nylon spacer (about 3" with a 1/4 hole through it) for the feedpoint. It's drilled and tapped for some set screws to hold it together.

Also...  I decided to purchase a small MFJ 6 meter tuner, which is inserted right out there at the feedpoint.  It's takes a little work to get it adjusted (even using an MFJ analyzer, things change by the time I get the coax hooked up inside), but that eliminates the 75 ohm stub, which I couldn't get right in 100 tries. I cut, cut, cut some more... replaced it again, cut again -- all until I was blue in the face.  The little tuner at the feedpoint is just magic in comparison.
« Last Edit: January 09, 2012, 04:34:25 PM by K7ZRZ » Logged

Brian K7ZRZ
LZ1MAK
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Posts: 5




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« Reply #6 on: January 10, 2012, 04:28:31 AM »

Thank you all,
great forum with nice people! The antenna is up, later I will adjust it because I made it little longer. For I can say only that is is little beast. There is difference between the dipole and the loop antenna, I like it.
K7ZRZ, the antenna  is for 10 meters, from a copper wire. My next project is to make next one from Aluminum, 5/8 wave vertical inside the fishing rod.
Once again thank you very much my friends, wish a great year to all of you!
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