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Author Topic: Elevated 4BTV - radials only on one side. Waste of time?  (Read 3022 times)
K8DJW
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Posts: 32




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« on: May 17, 2013, 08:33:40 AM »

While it would be possible to mount the antenna in the center of my roof and extend "tuned" radials down the roof in all 4 directions, I'm trying to avoid this. I have a great place to mount on the edge of my house... for feed purposes it is ideal, and much more stealthy. But I could only extend radials out to one side... they would be to the east of the antenna.

Does anyone have any experience with this type of situation? Would my pattern be lopsided to the east (this is ok, I'd much rather it go east than west.)

And a somewhat related question - does the 30M "add on" remove the 40M capability of the antenna? It sounds like it does from reading the manual, but I can't tell for sure. If I know I wanna work 40M and 30M am I better off with the 6BTV?

Thanks for the help!

73!
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K5LXP
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« Reply #1 on: May 17, 2013, 11:31:12 AM »

Quote
I could only extend radials out to one side...
You can make that tradeoff if you want.  Performance will favor the direction of the radials is all.

Quote
does the 30M "add on" remove the 40M capability of the antenna?

If you're talking about the parallel wire add-on, it shouldn't.  It won't if you're talking about the trap kit. 


Mark K5LXP
Albuquerque, NM
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KO3D
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Posts: 49




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« Reply #2 on: May 18, 2013, 09:44:31 AM »

My radials extend to one side for the same reason. I'm sure if I tested it there would be a difference, but for practical purposes it works fine. Its not a waste of time.
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W4VR
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« Reply #3 on: May 18, 2013, 02:30:44 PM »

You have to do with what you've got!
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K3VAT
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Posts: 701




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« Reply #4 on: May 18, 2013, 05:33:08 PM »

While it would be possible to mount the antenna in the center of my roof and extend "tuned" radials down the roof in all 4 directions, I'm trying to avoid this. I have a great place to mount on the edge of my house... for feed purposes it is ideal, and much more stealthy. But I could only extend radials out to one side... they would be to the east of the antenna.

Does anyone have any experience with this type of situation? Would my pattern be lopsided to the east (this is ok, I'd much rather it go east than west.)

And a somewhat related question - does the 30M "add on" remove the 40M capability of the antenna? It sounds like it does from reading the manual, but I can't tell for sure. If I know I wanna work 40M and 30M am I better off with the 6BTV?

Thanks for the help! 73!

In addition to the comments above, if you want a technical explanation of what may happen with non-symetrical radials on a vertical antenna check out this link:  http://rudys.typepad.com/files/qex-ground-systems-part-7.pdf  While this pertains to ground mounted systems, one may infer certain parameters over to elevated radial systems.  (the article comparing ground mounted and elevated radial systems is part 3.)

As you can see from the link title, this is part 7 - if you're so inclined, the early parts are a must reading for a good, solid understanding of radial systems.

GL, 73, Rich, K3VAT
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KA7NIQ
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« Reply #5 on: May 19, 2013, 02:35:16 PM »

While it would be possible to mount the antenna in the center of my roof and extend "tuned" radials down the roof in all 4 directions, I'm trying to avoid this. I have a great place to mount on the edge of my house... for feed purposes it is ideal, and much more stealthy. But I could only extend radials out to one side... they would be to the east of the antenna.

Does anyone have any experience with this type of situation? Would my pattern be lopsided to the east (this is ok, I'd much rather it go east than west.)

And a somewhat related question - does the 30M "add on" remove the 40M capability of the antenna? It sounds like it does from reading the manual, but I can't tell for sure. If I know I wanna work 40M and 30M am I better off with the 6BTV?

Thanks for the help!

73!
Grin I promise not to tell anyone, that you only have radials on one side of your elevated vertical, if you also promise to keep it secret.
Do what you got to do to get on the air, and have fun.

LOL, for all you know, you live over an old abandoned copper or salt mine, up there in 8 land.


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N6AJR
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« Reply #6 on: May 19, 2013, 07:11:10 PM »

go for it, every little bit helps.
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WX7G
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« Reply #7 on: May 20, 2013, 03:15:36 PM »

With radials on one side only the antenna is no longer a ground plane, it is a dipole. One half of the dipole is horizontal and low while the other half is vertical. It will still work well enough.

If you mean the 30 meter trap, it does not affect 40 meter operation.

You might want to place a 1:1 current choke at the feedpoint to reduce feedline radiation.
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W5WSS
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« Reply #8 on: May 20, 2013, 05:33:30 PM »

Dave wx7g is correct.

Consider routing pairs of tuned radials from the shield driving feed point holding parallel to the end of the house while sloping downwards and traveling away opposite each other to non conductive anchors. The antenna will behave properly relative to pattern maintaining omni directionality.You have the option of using only two for monoband operation or adding more tuned sloped pairs for multi band operation along with a wide range tuner and a 1:1 current balun.

73

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WX7G
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« Reply #9 on: May 20, 2013, 11:58:03 PM »

A NEC model of a 14 MHz vertical with the base 20' above average ground and having one radial extending to the east shows 2 dB more gain (at a take off angle of 10 deg) to the east than to the west.

Compared to two symmetrical radials the gain at a take off angle of 10 degrees is down 5 dB to the west and 1 dB to the east. The "missing" radiation is being radiated by the single radial at high take off angles.

I have built and used single radial verticals and they did the job.



« Last Edit: May 21, 2013, 12:02:20 AM by WX7G » Logged
K8DJW
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Posts: 32




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« Reply #10 on: May 21, 2013, 06:21:01 AM »

Thanks all for the encouraging responses! Now it's just a matter of finding some stealthy radial wire that's more or less invisible on my roof. I can probably get at least 8 radials up, maybe more. There will be a ground rod directly under the antenna (about 12' below) and it will be connected with very heavy copper. But lets not get into grounding. Smiley

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W5WSS
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Posts: 1652




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« Reply #11 on: May 21, 2013, 07:36:16 AM »

 Two elevated tuned symmetrical radials originating also at 20ft (The trap quarter wave multiband vertical base height) traveling in opposite directions, sloping downwards,at a range of angles,also involves feed point RR  and dc isolated from earthing at their radial end is balanced and should not model such a difference especially relative to pattern.
This type of technique creates a vertical multi band center fed dipole incorporating equal distance and balance splitting the singular downward element into two equal parts and is maintained because of the symmetrical positioning of the split second leg halved into two equal parts holding  balance then as a result omnidirectional radiation is preserved and within this polar pattern angles sampled will IE 10 degrees of manifested power measurements hold to convention.
That is not to say that real life surroundings could slightly to significantly couple radiation in varying ways.

When a antenna described as a vertical half and a horizontal half is center fed where the horizontal half is at the top and held horizontal the antenna is a center fed dipole and the horizontal leg radiates horizontal radiation broadside to the wire axis while the verticalthat drops downwards this half leg radiates vertical radiation in the E plane around the vertical positioned leg. and the feed line can become more involved as an additional radiator to some measured extent even when DE coupling the feed line provision is included.along with the earth surface a better way to control some of these UN wanted manifestations is in using equidistant techniques relative to radial positioning around the vertical for a better effort to maintain omnidirectional development of vertical radiation around the compass .

73

73
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K7KBN
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Posts: 2765




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« Reply #12 on: May 21, 2013, 09:41:42 AM »

An hour of experimenting with YOUR antenna at YOUR station trumps several days' discussion on an Internet forum.  Get it on the air and see if it's a waste of time (by your own standards) or not.
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73
Pat K7KBN
CWO4 USNR Ret.
W5WSS
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Posts: 1652




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« Reply #13 on: May 21, 2013, 12:23:45 PM »

A really good performing HF omni directional vertically oriented vertically radiating antenna used from a base height of 20ft incorporates a quarter wave vertical element in conjunction with two or more sloping quarter wave radials along with a 1:1 choke.

There is no reason to preclude the trapped version vertical element from a properly designed sloped radial system from a performance perspective although in the end it is a users choice relative to ones specific installation requirements and need to be taken into account. The sloped radial system relative to either a multi band arrangement or mono band version will work well.

I built a 15M mono band version from wire Looked like a peace sign using three exacting wires.(along with many other antennas over the past 40 years)  and hung it from a high tree (the tip of the top end of the 1/4 wave vertical wire was attached to an insulator and rope tied to the other side and hoisted up and dead ended using an non conductive ground anchor) and held in position where the base height was about 1/4 wave above the ground, included a choke at the feed point and two identical and identically sloped symmetrical wire radials held taught an an angle of 45 degrees with non conductive guy ropes and non conductive anchors.

Nothing wrong with experimenting.

The exchange of information here is the intent of this forum and meant to help others that asked for ideas not a waste of time to accumulate some information first.

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K8DJW
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Posts: 32




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« Reply #14 on: May 22, 2013, 04:35:41 PM »


The exchange of information here is the intent of this forum and meant to help others that asked for ideas not a waste of time to accumulate some information first.



Yeah, I tend to agree. If asking questions in these forums is a bigger waste of time, what are we all doing here? Smiley

I don't have the antenna yet. But this will be my first vertical and before investing the money and time into it I just wanted verification that it *could* work. Sounds like I need to get it ordered and get that sucker up!
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