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Author Topic: Fan Radials, as in a fan dipole.  (Read 1025 times)
K1FPV
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Posts: 33




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« on: April 05, 2013, 02:11:25 PM »

I'm somewhat curious. I recently acquired a Hy-Gain 12AVQ. I'll be mounting it up in the air so that I'll need radials. Hy-Gain recommends 2 radials per band (6 in all). I previously used a 14AVQ back about 45 years ago with just 4 radials cut for 7 mHz. and it worked great on all bands with a good SWR.

I'm trying something different this time. I'm going to use 4, 16½ foot sections of 450 ohm ladder line. One lead of the ladder line will be the full 16½' and the other lead cut to 11' 4". I'll then weave a third wire as the 10 meter radial between the 2 leads of ladder line to a length of 8' 4" in length. This will give me technically, 4 radials per band in a perfect quad arrangement with the radials each being separated by 90 degrees. It theoretically should work!

Has anyone ever tried this?

Thanks in advance,
Bill/K1FPV
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K7KBN
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Posts: 2814




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« Reply #1 on: April 05, 2013, 02:56:35 PM »

It just might work.  This would be one of those times where you could save a lot of time by experimenting and seeing just what happens.  What works?  What doesn't?  What works, but should work better?
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73
Pat K7KBN
CWO4 USNR Ret.
KB4QAA
Member

Posts: 2409




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« Reply #2 on: April 06, 2013, 01:16:39 AM »

Sorry, but you are essentially re-inventing the wheel.

Hams have used multiconductor cable, like flat rotor control cable with the wires cut to different lengths as radials for years.  It works!

Radials is radials; let's leave the word 'fan' out the fight!  Smiley
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W5WSS
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Posts: 1745




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« Reply #3 on: April 06, 2013, 05:20:29 AM »

Yeah I used the technique of fanned, sloping, elevated, tuned radials at a summer cottage in Tenn.
I used a series of quick change (apx 3 minute to do) vertical wires, one for the higher bands 10m-15m, one for 17m to 30m and the longest wire for 40m to 160.I would choose the one I wanted and  I could hoist up and down pulling the tip up and hold in the vertical position. Hoist up or down over a 90ft high tree limb using Dacron rope.
The system of radials were attached directly adjacent to the antenna lead for a complete feed point at the base.
The strain relief was a dogbone insulator attached to a short length 2" OD schedule 40 pipe anchored into the ground and was dc isolated from earthing. I used a phenolic plate as a junction for the feed line, antenna and radial connections. I used a wander lead to a earthing rod and disconnected the antenna wire from entering the shack this redirected the antenna to the earthing rod outside for lightning potential or when I was away...Having said all that for an effective radial system to add to the antenna vertical wire from the Phenolic plate junction I added pairs of elevated dc isolated insulated #14 copper wires for each band yes the radials were tuned for the center of the respective band. They were separated only in the angle by which they sloped downwards toward the ground for attachment to yes insulated anchors. The radials traveled in opposite direction relative to it's counterpart from the feed point junction.
I used an auto tuner weatherproofed at the antenna and radial junction and only needed 3ft of 52 ohm coaxial cable to link the auto tuner to the equipment because the antenna originated just outside the shack window at an elevated height of about 4ft. and 3ft of coaxial line would reach from there to the equipment.
This system was effective and the antenna radiated as much erp field strength as is possible with the length of vertical portion being held to a range of between 1/4 wave to 5/8 wave for good power manifesting at low angles for hf long range dx work.
The radial system completed the antenna provided a push platform for the vertical portion and changed the definition of this system to center fed elevated vertical.
When the radial system was installed the surge impedance was lowered to a very manageable and was mostly non inductive and very easy on the tuner which is needed when we press a vertical antenna element into ranges of multi band service.
The fanned radial system I used worked to complete the system and common mode displacement currents compared to an end fed wire were not measurable.
73
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K2TTM
Member

Posts: 51




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« Reply #4 on: April 06, 2013, 10:31:34 AM »

I have a question about the number/length of radials.  I'm contemplation putting up a multiband vertical in my yard where I will only be able to lay down radials of approximately 15' in length running West & North.  In the NE to SW direction I can lay down radials as long as 50-70' depending on obstacles such as trees etc and finally, looking South I'd be limited to around 15-20' again.

My question is this. Do I try to keep all my radials the same length i.e. about 15-20' or should I take advantage of my property & lay them out in the way I described?  Am I correct to assume that laying them out asymmetrically will give me increased directivity in the direction of the longer radials?

Thanks for the help.

Mike/K2TTM
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99.9% of the time I'm on the air, I'll be on CW.
K1FPV
Member

Posts: 33




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« Reply #5 on: April 06, 2013, 10:44:05 AM »

I have a question about the number/length of radials.  I'm contemplation putting up a multiband vertical in my yard where I will only be able to lay down radials of approximately 15' in length running West & North.  In the NE to SW direction I can lay down radials as long as 50-70' depending on obstacles such as trees etc and finally, looking South I'd be limited to around 15-20' again.

My question is this. Do I try to keep all my radials the same length i.e. about 15-20' or should I take advantage of my property & lay them out in the way I described?  Am I correct to assume that laying them out asymmetrically will give me increased directivity in the direction of the longer radials?

Thanks for the help.

Mike/K2TTM


Well Mike, I would think if you can make them longer, at least a quarter wavelength or as close to it as possible, the better! If you can make them as long as a quarter wavelength, then make them as long as you can. Also, the more radials, the better.

Bill/K1FPV
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AD6KA
Member

Posts: 2238




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« Reply #6 on: April 06, 2013, 07:33:16 PM »

Quote
Sorry, but you are essentially re-inventing the wheel.

Hams have used multiconductor cable, like flat rotor control cable with the wires cut to different lengths as radials for years.  It works!

Yup. Butternut even sells it's STR-II "multiband radial kit" for the
HF6V and 9V made with 300 ohm twin lead, notched to make various resonant
elements similar in fashion as you describe. So Window Line should work the same,
though it may take some experimenting as the other poster said.

The Butternut radial kit is ridiculously expensive! (also contains
enough plain insulated wire for a couple 80m radials)
but still at $170 is insanely overpriced.
http://www.hamradio.com/detail.cfm?pid=H0-004038

I've thought about experimenting with reproducing that multiband
radial kit with Window Line......and if it works well perhaps
selling them at hamfests. But I don't know how well they would
sell or what the price break would be. Hams are notoriously cheap,
and making individual band radials is easy and cheap.

Good luck with your window line multiband radial
experiments.....and please do let us know how it turns
out. I'm quite curious to hear the results, especially the
"weave a third wire as the 10 meter radial between the 2 leads of ladder line" part.
73, Ken  AD6KA
 
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