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Author Topic: An idea that has worked for me.  (Read 16643 times)
N4NOO
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Posts: 106




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« on: January 22, 2014, 10:55:59 AM »

I live in a restricted area and I am not supposed to have any outside antennas.  This is what I did.  The back of my house faces an area outside of my neighborhood and can not be seen from the front of the house. I have been very successful at using an inverted-L antenna.  At the back of the house I have a 30 foot mast (which does not extend above the roof and can't be seen from the front of the house) anchored to the house with a bracket (Radio Shack) at about 22 feet off the ground.  At the base of the mast, I have a coax feed Balun. The Ground lug feeds about 12 - 100 foot long radials that are spaced about one foot apart and run under the antenna wire.  The "hot" lug from the Balun has a 22 gauge black plastic-coated copper clad steel wire that runs from about one foot off the ground to the top of the mast and the across the back yard to the top of a tree.  With a tuner, I can work all bands from 160 to 6 meters.  Not as good as a lot of other antennas but I can have a lot of fun!  I hope this helps someone get on the air!
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WV4L
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« Reply #1 on: January 25, 2014, 06:53:41 AM »

Feb. issue of QST has a nice article that is similar to your set up.

73 

Wayne C.
WV4L
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W1VT
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« Reply #2 on: January 28, 2014, 06:00:26 AM »

While a ground rod won't help your signal, you should install a single point  ground for lightning protection.  I use a sufficiently long lengths of coax to conveniently locate the entrance panel for the station near the service entrance so that lightning doesn't have to go around any corners. 

Zack W1VT
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W4OP
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« Reply #3 on: January 29, 2014, 06:49:43 AM »

The whole concept of a BALUN is that the outputs are balanced- there is no hot or ground lugs. Perhaps you are using an UNUN?

Dale W4OP
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W5WSS
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« Reply #4 on: January 30, 2014, 01:58:12 PM »

I built a similar multi band system at a summer cottage in Tennessee In 2012 and used it for 8 months.

My slightly (almost vertically oriented) 5 degree relative to plumb wire system including slightly elevated wire radials consisting of tuned Pairs of 1/4 wave sets per band fanned downwards from the enclosure box traveling opposite direction relative to each other and anchored to the earth with non conductive tent stakes and were dc isolated  all was held in strain relief at about 5 ft above ground using a non conductive 6ft x 2" pipe and concrete base.

For lightning protection of the equipment beyond the $10 antenna wire *Note the antenna wire can be destroyed and is not protected by large or direct hits but the equipment on beyond will be better protected.

Here are some suggestions: For off the air thunderstorm potential and/or to use when away.

 This system should be as far away from the coaxial entry as possible with a ground rod driven into the earth right next to it's base. Ideally the rod should be cadweld bonded to the ac mains rod with a solid copper #6 wire.

I mounted a weather proof enclosure at the top end of the pipe because I wanted to utilize an elevated system, The enclosure  Can be at the bottom for ground mounting and ease of connecting up ground radials.

 The antenna system feed point located Inside the enclosure should Ideally include a small bus bar, a coaxial in line center conductor lightning arrestor accomplishing protection for  both center conductor and the coaxial shield being bonded to the bus bar and using a 3"wide short copper strip connecting/bonding the bus bar to a ground rod located next to the antenna base. I did not do it that way at the time, instead (both of these can be combined) I used a wander lead that I permanently connected to the ground rod and would connect the other end to the antenna wire before it entered the box. Inside the box and after the strain relief I made a provision to disconnect the antenna element and move it away slightly and disconnect the coaxial cable lead in at the box exit as an extra precaution.

So just prior to entering the box the antenna element was diverted to the ground rod with the wander lead prior to physically entering the box and everything leaving the box was disconnected even though during the travel towards the shack entry the coaxial shield was periodically bonded again to earth twice at even intervals using two more rods and the connections were treated for corrosion prevention.


The purpose of the wander lead was to open the antenna out far from the entry and divert the antenna lead directly to the rod even though the coaxial head in shielding was bonded the center conductor was broken open while the arrestor was there for the purpose of static electricity bleed-off and some measure of additional lightning protection I relied on opening the antenna element with the wander lead for Thunderstorm potential and relied on the arrestor for static bleed off during operating on the air.

This all sounds complicated but really is not.

The top end of the antenna element was knotted to a ceramic dog bone type insulator and the opposite side was knotted to a hoisting rope that traveled over a strong branch and routed down tied to a strong dead end, enough slack was included to lower the antenna tip to ground and was lowered several times which was an added part of avoiding high expected winds tree branch sway and when I wanted to place the antenna wire at the ground level to avoid a high antenna point up in the air.

The system included a auto tuner and a 1:1 current unun balun choke that can be high power capable now  designed to be remotely operated and installed in the enclosure. I used a male to male adaptor to link the balun directly to the tuner output connector.

I never had lightning damage but admittedly was concerned about the pulverizing variety strokes that are common in the higher mountainous regions and an expensive tuner.

The layers of the protection and common sense and luck.

The performance can be expected to rival an Omni directional elevated vertical and shrinking vertical antenna element when changing bands but in all cases when the antenna element is pressed into service where it's length by percentage is within a range of the 1/4 to the 3/4 wave this can be the case.

I was able to hoist down the antenna element and quickly exchange it with one of three pre made lengths 25ft, 41ft, and 66ft.

I already owned the tuner the balun. The cost was minimal for the rope ,radial stakes, dog bone insulator and 500 ft spool of#14 Thhn stranded wire (optional).

The value of the system priceless! I had a ball working allot of dx long range sky wave and state side too!

73

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N4NOO
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« Reply #5 on: January 31, 2014, 07:38:07 PM »

The whole concept of a BALUN is that the outputs are balanced- there is no hot or ground lugs. Perhaps you are using an UNUN?

Dale W4OP


Dale, You are quite right!  My mistake.  I am using a Balun Design "UnUn" Model 2135 Custom 50 ohm to 100 ohm.  The antenna when measured with an analyzer had about 100 ohms at the desired frequencies.  I talked with Bob and he custom built a 50-100 ohm with a 5KW rating.

As for the ground rod, there is one at the connection point to the ground system.
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KD4LLA
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« Reply #6 on: February 23, 2014, 02:44:34 PM »

While a ground rod won't help your signal, you should install a single point  ground for lightning protection.  I use a sufficiently long lengths of coax to conveniently locate the entrance panel for the station near the service entrance so that lightning doesn't have to go around any corners. 

Zack W1VT

"The Ground lug feeds about 12 - 100 foot long radials that are spaced about one foot apart and run under the antenna wire."

How much "ground" should a person have?

A lightning strike to the house and dangling a wire w/ in a few inches of one's house is going to be safe because of a ground rod?  Is the phone/ Internet entrance grounded?  How about the cable TV/ DirecTV cable entrance?

Mike

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N4NOO
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« Reply #7 on: February 24, 2014, 01:46:59 PM »

Well, Mike I can't answer "how much" ground is needed for lightning protection but I have the radials simply as the "other half" of my antenna. And I must say, they make a great deal of improvement in the antenna. 
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N4JTE
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« Reply #8 on: February 25, 2014, 03:14:35 PM »

Not to move off topic too far but after living in south fl for 20 plus years with various wire antennas, I never bothered to install any kind of lightning grounding elaborate system as my wires were so thin, relatively they presented a small fuse to any nearby lightning and did the trick. Now if I had a 100 ft tower with a few beams I would have done my due diligence, hi. Of course I threw all coax out the window also, hi.
Bob
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KI5WW
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« Reply #9 on: February 28, 2014, 11:54:40 AM »

Not to move off topic too far but after living in south fl for 20 plus years with various wire antennas, I never bothered to install any kind of lightning grounding elaborate system as my wires were so thin, relatively they presented a small fuse to any nearby lightning and did the trick. Now if I had a 100 ft tower with a few beams I would have done my due diligence, hi. Of course I threw all coax out the window also, hi.
Bob

Hope your system works cuz i use the same system here in Oklahoma. I was stationed in fla in the military. Whats the deal on lightning down there?  We fear f5 tornados here but there in fla we feared extremely Violent and deadly lightning. Never seen anything like it.
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W8JI
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« Reply #10 on: March 01, 2014, 06:06:06 AM »

The whole concept of a BALUN is that the outputs are balanced- there is no hot or ground lugs. Perhaps you are using an UNUN?

Dale W4OP


Dale, You are quite right!  My mistake.  I am using a Balun Design "UnUn" Model 2135 Custom 50 ohm to 100 ohm.  The antenna when measured with an analyzer had about 100 ohms at the desired frequencies.  I talked with Bob and he custom built a 50-100 ohm with a 5KW rating.

As for the ground rod, there is one at the connection point to the ground system.

We get all hung up on names when function is important.

A current balun is an unun with common mode isolation. A current balun functions as anything from an unun to a balun.

So technically, certain types of  baluns can function as unun's, and actually be better than ununs. In your case a current balun used as an unun would serve to isolate common mode, as well as do the 100 ohm thing, although I'm not sure you need any impedance transformation. Because the impedance is 100 ohms on a meter doesn't mean a 100 ohm to 50 ohm transformation matches anything. What if the impedance is mostly reactive?

What was the real and imaginary part?

If the ground rod is not bonded to the power mains ground with low impedance and/or if you have no entrance ground that is bonded to the mains ground with low impedance, you have a hazard.

Good luck on throwing a cable out the window and calling it protection. Smiley
« Last Edit: March 01, 2014, 06:09:53 AM by W8JI » Logged
N4NYY
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« Reply #11 on: March 02, 2014, 05:32:54 PM »

Quote

If the ground rod is not bonded to the power mains ground with low impedance and/or if you have no entrance ground that is bonded to the mains ground with low impedance, you have a hazard.


Hey, I did this by looking at your site. I have an entrance panel and bonded my electric service panel to it using 4 gauge. I should post a pic.
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KD8NGE
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« Reply #12 on: March 08, 2014, 09:18:10 AM »

 Well done;D and well thought out, excellent use of available resources and especially kudos for your groundfield!
You are most correct, the ground field will enhance your antenna!
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