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Author Topic: best wire antenna for a 150' space ?  (Read 1924 times)
W8JI
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« on: September 20, 2003, 09:11:22 PM »

I'd go along with a center fed antenna 130 ft long using ladder line, but I certainly would NOT use a 4:1 balun!!!

4:1 baluns have the higher loss and narrower impedance and frequency range when compared to a 1:1 balun. Plus they are generally voltage baluns, which offer the poorest balance.  

The input of the feedline is never 300-500 ohms, so it makes no sense to use a 4:1 for matching reasons.

I'd use a good 1:1 current or choke balun and make the feedline 25-35 feet long, or around 85-95 feet long. Use a good tuner, and you will have about the best antenna you can install in a small area.

73 Tom
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KE4ZHN
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« Reply #1 on: September 20, 2003, 07:46:27 PM »


Hi Dave. Although some Im sure some will disagree, Id try the old stand by classic center fed doublet. Its 135 ft total length, and all youd need is a remote balun outside connected to your already run coax feed and use your tuner to load it up on all bands 80-10. I used a set up like this with excellent results and can talk to anyone I can hear anywhere on the planet barefoot or QRO. Your lot is perfect for one of these and this antenna has been in use since the 1930`s! Van Gordon makes one ready made thats so cheap you cant even make one yourself for less money (around $30) I use a Centaur B41W10-50 remote balun, but in your case since your not running an amp, any good quality 4:1 balun should work fine. Just keep the coax run short and keep the 450 ohm line away from metal, like gutters and downspouts and try to avoid sharp bends and it will play like a bandit on all the bands. Im sure others will argue or discredit this tried and proven old antenna, but all I can say is, mine works terrific and I wouldnt recommend it if it was junk. Good luck Dave, catch you on the bands.

73 Rich  
       

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K0ZN
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« Reply #2 on: September 20, 2003, 11:11:05 PM »


I would offer four suggestions.

(1.) The basic 135' Center Fed Dipole also called the Center Fed Zepp, fed with 450 ohm or 600 ohm open wire line. The TRULY best and most correct way to match that antenna and transmission line system is with a true balanced tuner. A balun is not needed in this case, because the tuner has a TRUE balanced output. If you can find one, a Johnson Matchbox (in both 300 W and KW) are supurb pieces of equipment, but probably kind of hard to find. A new modern alternative is the new Palstar unit that is designed SPECIFICALLY for balanced line. These units will give better balance and lower loss than anything else. Under any circumstances, a balun in a highly mismatched situation (high SWR) (which will be the case on almost every band with a C.F. Zepp)is at best a compromise. MOST baluns are NOT designed to operate at high SWR and, if you so choose, high power. Voltages can become very high (several thousand volts) and will quickly destroy most commercial baluns. SOME baluns are specifically designed for this type of service. I don't know if they are still made or not, but Palomar and Amidon Associates made and may still make them. These units have very high quality teflon insulation to avoid arc over and other problems related to high voltages and mismatch. Note that these are both 4:1 baluns. I would respectfully disagree with the suggestion to use a 1:1 balun... especially at anything other than a low power level. Dr.Jerry Sevic, W2FMI, who is the The Guru on Transmission Line Transformers & Baluns, recommends the 4:1 in this application and Amidon makes a unit built to his design spec's. The ARRL has his book Transmission Line Transformers available and you can read his explanations if you so desire. Again, if you want to do it "right", get a tuner that is designed for Balanced line. FYI: Virtually ALL commercial Tuners except the Palstar and Johnson units are some form of UNbalanced tuning network connected to an "internal" balun. That doesn't mean they don't work...it justs means you still are trying to force a balun to do something it really isn't intended to do; match high reactance loads.

(2.) Antenna wise, another option is a Full Wave 80 M loop. There seem to be a lot of people that swear by large loops. They are frequently a little quieter on receive than a linear antenna. You would feed the loop just like the Center Fed Zepp...with a parallel balanced line at the center of one side or in a corner and tuner (or balun and tuner). A balun might fare a little better in this situation, because the raw SWR *might* be a little lower than on a 135' center fed. Some people report decent results just feeding the antenna directly with coax to a Tuner, but I would think that might be pretty lossy unless the coax line is pretty short. The disadvantage to the loop is the need for 4 separate support points.

(3.) A Fan Dipole: multiple dipoles all connected together at the feed point and fed with a single transmission line. A good 1:1 balun would be advised here and the antenna fed with coax. Unless you want to do a lot of "cut and try" to get the SWR low on each band, a Tuner is pretty much mandatory as there is some interaction between the dipoles and the SWR will likely be moderately above 1:1 on most bands. Regardless, the SWR on this antenna will be "reasonably low" at the feed point. If you use this antenna, start your "tweaking" on the highest band and work down. You probably will need a center support as the center weight is moderately high with coax feed.

(4.) An "inverted L". This is a good antenna on the lower bands, but matching is somewhat complex on multiple bands. It also requires a decent radial system to work well, but it can give good results on 160 meters if you have an interest in this band, which the other antennas above will not.

One last item to keep in mind if you elect to go with a 135' center fed and a balun....which will work....  Keep the coax portion of the system VERY short, because the SWR on some bands will be VERY high...like more than 10:1. At this kind of SWR the losses in coax are TERRIBLE.... especially at higher frequencies. Even a 15' piece of "good" foam coax at, say 6:1 SWR, which is entirely possible SWR, could be 2db on the upper HF bands!! i.e. 1/3 of your power would be disappated in the 15' piece of coax on 10 meters!! This is where the 600 ohm open wire line really shines...it is still VERY low loss at high SWR. The 450 ohm ladder line isn't too bad, but a LONG run of coax at high SWR can easily absorb 80%+ of your transmitter output! Also, the voltage on the line at high SWR and high power are often WAY in excess of the insulation ratings on coax, which is a problem. Keep the balun near the tuner and make the long run out of the 450 or 600 line. Some time and money WELL spent would be to study the ARRL antenna book and/or ON4UN's excellent antenna book: "Low Band DXing". There are a lot of good possibilities in a 150 area! Good luck.

73
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VA2DV
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« Reply #3 on: September 20, 2003, 03:51:31 PM »

Hi !
I just moved from an apartment to a brand new house.
I am planning to put a tower and a beam in the future
(enough expenses for the moment...says the XYL...)
but for now , i would like to put some wire in the air
to be back on the bands.The available space is around
150-175' between two big threes.The maximum height
that i can attach something is around 38'-40'.
I would like to know what type of antenna will work
best for this situation.I was almost decided for a G5RV
but i am sure there is other options.I am working
10m-80m at 100w and i do have an external antenna tuner
but he does not have a balanced input.The coaxial cable is already installed from the shack to the exterior of the house.
Any suggestions ?
Thanks for your help ,
Dave VA2DV
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W0UCE
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« Reply #4 on: September 20, 2003, 04:30:53 PM »

Dave:

I recommend you consider a Windom antenna from Radio Works, they offer a wide range of multi-band wire antennas.  I have used the 160-10m model for years with tremendous results. Here is the URL:
http://www.radioworks.com/

73,
Jack W0UCE
Raleigh, NC USA
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N6AJR
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Posts: 9888




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« Reply #5 on: September 21, 2003, 12:03:08 AM »

Do a Fan Dipole, it will cost you about $15 to make one, and all of 20 minutes.  Ues it with a tuner and you don't have to worry about precission tuning of the wires.

we are talking a coax long enough to go from the antenna to the rig. center conductor goes to one leg, the shield to the other leg. dipole = 2 legs the same length.  any wire strong enough to  hold up with out breaking (14-2 from home depot is like $15 for a 250 foot roll wich gives you 2 leads per length. strip it out.


160 is about 266 feet per side ( too long for you but 80 meters will tune here with a tuner..)

80 meters is 133 feet long per side.
40 is 66 feet per side.
20 is 33 feet per side.
15 will tune on 40 (harmonic)
10 is 8 feet 6 inches,
6 will do at 54 inches per side,
2 meters is 20 inches per side.
440 is about 7 inches per side.

these are all a bit long, but easier to tune with added capacitence on a tuner, thats why there are 2 caps and only 1 coil on most tuners.  Other wise tune them for minimum swr on your favorite freqs.

water proof the connection at the coax. put it up in and inverted V with each hanging below the other or put 80 north and south and 40 east and west and 20 caddy corner etc... fan them out, for less interaction, use a center pole and if the ends on the 80 dipole are too long then turn them and  run them down the fence . the rest tie a rope to the ends ( I use 1/4 inch nylon rope) and tie off where ever.  

its cheep so the wife will like it. choose the bands you want and only use those wires.  It is better than most verticles, and has been a main stay of ham antennas for years.  to improve on it you will have to go to a beam.  

Put it up as high as you can in the center and realize most of the radition is from the middle , less on the far ends.  No radials needed. You can use the antenna to be the guys for the mast, and you did it your self.

do a search here on LMERS SEARCH for Fan Dipole , also known as a multiband wire dipole.

what happens is that a 40 meter signal will see the 40 meter dipole as a 50 ohm (+-) load and most of the power goes here, the other antennas being non resonant will look like several hundred to several thousands of ohm impedeance (not resistance) and little power goes there.  Sort of like a log periodic but easier and cheeper. They work and work well. You will have the average 5/5 antenna in a net with 30 people, some will be stronger, with power and a beam, and some will be weaker, and this is just abut the mid line antenna. it will take 1500 watts of power if your wire is bigger than about 18 gague.

hope this helps

tom N6AJR
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N6AJR
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« Reply #6 on: September 21, 2003, 12:07:28 AM »

P.S.  you can use a 1 to 1 balun in the center if you want, not necessary, but makes it easier to build, see BUXCOMMCO.COM for cheep 1:1 baluns.... also if you get rf in the shack ( mike biteS from RF) then make a 6 or 8 turn 6 inch coil of coax ( tape it or use zip ties to hold it in shape) at the antenna feed, or at the rig , or both. These are known as coaxial baluns and remove rf from the outside of the shield. But not usually necessary.
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W3DQ
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« Reply #7 on: September 21, 2003, 06:05:43 PM »

My interest is 160/80/40.  I presently have an OCF wire for 80/40 (a Fritzel).

Q:  How long is the 450 ohm feedline and where is the transition to coax (or is there one) so I can get the feedline into the shack?  It will be about 70 feet from the antenna to the tuner (TT 238).

Eric W3DQ
Washington, DC


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W3DQ
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« Reply #8 on: September 21, 2003, 06:06:25 PM »

My interest is 160/80/40.  I presently have an OCF wire for 80/40 (a Fritzel).

Q:  How long is the 450 ohm feedline and where is the transition to coax (or is there one) so I can get the feedline into the shack?  It will be about 70 feet from the antenna to the tuner (TT 238).

Eric W3DQ
Washington, DC


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N5CRO
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« Reply #9 on: September 21, 2003, 06:15:24 PM »

 Hi Dave
Seem like you got enough space but not much height for lower bands,anyway try N4GG array..you can decide how many bands you want to cover.With this antenna you will get good low angle radiation and tuner free multiband operation by using just 50 ohm coax.I did not have enough space so I built it from 30m and up!This antenna realy works good.

 [http://www.arrl.org/members-only/tis/info/pdf/0207035.pdf]

qst magazine Jul 2002

73 Josip N5CRO
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ZL4AI
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« Reply #10 on: March 02, 2007, 03:32:07 PM »

N4GG is an amazing DX antenna!!!!!!
Very Quiet on receive, and puts out amazing power at low angles at large percentage around a circular azimith. A 20 / 40 multi band will work with upto 10.2 dB dBi on 20. Also good power on 40 and 15. That's much better performance than any alternative wire antenna. My modelling shows that its performance changes little if the legs are at ground level or elevated. It works well at very low heights of say 40 feet.

It has just one down side. You dont hear many local signals. Its is not good for local traffic. I sometimes hear stations in the North of New Zealand, from my QTH in the south. I cannot hear signals 400 kms away on 40 m. I start hearing well at Australia 1,500 kms off.

A ladder line fed version with a tuner has worked well. This increases the flexibility, of not establishing reasonance, but introduces some tuner losses. Send me an email if you want a QSO to see how well this antenna works with just 100 watts.
ZL4AI
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ZL4AI
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« Reply #11 on: July 26, 2013, 08:00:06 PM »

Here is link explaining why the ZL4AI-N4GG array works so well

http://www.jking.netau.net/ZL4AI-N4GG_01.htm

Hopeful other will build one and experience the advantage of 10.4 dBi in four directions at once

73s
ZL4AI
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W9KDX
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« Reply #12 on: July 27, 2013, 06:23:28 AM »



80 meters is 133 feet long per side.
40 is 66 feet per side.
20 is 33 feet per side.
15 will tune on 40 (harmonic)
10 is 8 feet 6 inches,
6 will do at 54 inches per side,
2 meters is 20 inches per side.
440 is about 7 inches per side.



tom N6AJR


Don't overlook 17 meters.  Some of my best contacts are on this band and for the last 6 months or so, and for the near future as the sun spots fall off, 10M, 12M, and 15M will be virtually empty.
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Sam
W9KDX
G3RZP
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« Reply #13 on: July 27, 2013, 10:51:51 AM »

Where did this oldie pop up from?

BTW, no antenna can get 10.4dBi of gain in 4 directions at once - unless the directions are of VERY narrow beamwidth. To get 10.4dBi in each of 4 directions means a total of  41.6dBi or over 1/10,000 of a sphere. That is then divided by 4 - go figure out the beam width for 10.4dBi in each direction.

N4GG didn't claim that.
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AC5UP
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« Reply #14 on: July 27, 2013, 11:10:24 AM »

BTW, no antenna can get 10.4dBi of gain in 4 directions at once

Glad you mentioned this as the ZL4AI link includes the remarkable phrase:  The diagram below on 20 metres as you can see produces power at 10.2dbi

As a passive device wire alone cannot produce power. Nor can a diagram. But, a directional antenna can exhibit gain... The venerable technique of subtracting radiated power from one (or more) direction(s) and adding it to another. The total radiated power remains the same, give or take radiation efficiency and ground effects, for a dipole or multiple wavelength array.

It's the radiation pattern and elevation angle that can give this antenna an advantage, and for my money anything that performs well at lower heights is worth considering.

Something about stringing $10.00 worth of wire between a pair of $500.00 towers just to exchange signal reports gives me reason to pause.   Wink
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