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Message |
    
Jessejames
Junior Member
Username: Jessejames
Post Number: 29
Registered: 2-2004
| | Posted on Friday, September 24, 2004 - 5:00 pm: | 
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Can someone help with this information.
How do you make the antenna?
How do you put it in line?
What do you make it out of?
How big should it be?
I read a post of someone working the world; 15 feet off the ground.
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Slugo4449
Junior Member
Username: Slugo4449
Post Number: 12
Registered: 7-2004
| | Posted on Friday, September 24, 2004 - 6:15 pm: |
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If the conditions are right then yes you can work the world on a piece of wire up 15 ft.
As far as making a dipole it is very simple. figure out the frequency that you want to use. say 27.205(channel 20). 468/27.205 = 17.2FT. Add two feet to this for trimming.
cut that in half. So you have 2 pieces of wire that are 9.6ft long each. Get three insulators. Can be plastic or ceramic or even wood. Attach the wire using about 6 inches of wire to wrap around itself through the insulator. Do that again on the other side of the insulator. Then attach an insulator on the ends of each wire using 6 inches to wrap around itelf.
What you should have is an insulator, attached to a piece of wire that is 8.6 ft long then attached to another insulator then another piece of wire that is 8.6 ft long then attached to another insulator.
Simply: insulator-wire-insulator-wire-insulator.
Strip off 6 inches of insulation from the piece of coaxial cable. Attach the center conductor of the coax to one side of the center insulator and then the braid to the other side.
That is a half wave dipole.
If you would like to adjust it....just lengthin or trim the lengths of both wires equally remembering that the higher the frequency the shorter the antenna.
Good luck!
CUL
Marty |
That ELCO Guy (Unregistered Guest)
Unregistered guest
| | Posted on Friday, September 24, 2004 - 6:26 pm: |
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A simple dipole is complsed of the following items.
Coax-enough to reach your radio with connector on one end of the coax.
Two lengths of wire.
Three insulators
Enough nylon rope to streach out the antenna between two supports
Tools needed:
Needle nose plyers
Side cutter plyers
Soldering gun or heavy duty soldering iron
Solder, rosin core
A roll of electrical tape.
Step 1: Cut two lengths of # 14 copper wire, insulated or uninsulated using the following math calculation. Length of each section in feet = 234 divided by the central operation frequency in Mhz. Add 8 inches to that measurement and cut two pieces of wire said length long. r CB that is about 108 inches.
Step 2: If insulated skin off about 8 inches of insulatin from one end of each of the above two lengths. Insert one of the lengths bare wire into one hole of an insulater, fold back and twist the bare wire on itself such that the bare wire twist touch the bare wire. Leave a short tab of bare wire sicking out (We will solder the coax to this tab later on. Leave the loop you made a little loose so that the wire can swing freely.
Step 3: Do the same thing with the other piece of wire inserting it thru the other hole on the opposite side of the loop you just made.
Step 4: Using the two remaining insulators insert the end of the wire of each length thru one of the holes of the remaining insulator. bend back the end and wrap the wire making a small loop.
Time out....
If you have an insulator followed by a length of wire, followed by a central insulator followed by the second length of wire with an insulator on its end as well.
Now the soldering part. Using the plyers hold the tabs in the center and solder the center conductor to one of the tabs and the shield to the other tab. Tape up the connections so as to keep water from seeping into the shielding braid.
INSTALL...
EASY part. Streach out the wire using the end insulators and the nylon rope between two objects. IF you put up a horizontal configuration you adjust SWR by changing the height of the antenna to the lowest SWR. Try to put the antenna at least 108 inches above the ground and keep it away from any metal buildings.
Now here is the bad news. The feed point has an impedance of 70 ohms more or less. The coax has an impedance of 50 0hms. The best SWR you will ever achieve (in theory) is 1.5--70/50. So if you get a 1.5 SWR and cannot get it lower do not panic. It is the best you will ever do with a dipole feeding it with a 50 ohm coax. To in theory get a 1.1 ratio on the ol SWR meter you will need to use 70 ohm coax to feed the antenna.
The gain on a dipole is reference or ZERO. However it will take whatever your feedline can take and you can throw into it.
In closing a Safety Precaution. Put the antenna where no one can touch it. If you use any kind of power the voltages will be very great at certain points on the wire. SOOOO do not touch or let anyone come into contact with the antenna while you are transmitting.
Hope I did not confuse you
That ELCO Guy
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That ELCO Guy (Unregistered Guest)
Unregistered guest
| | Posted on Friday, September 24, 2004 - 6:28 pm: |
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PS from Elco Guy to ol Jessie...
If you get confused, using Yahoo or whatever search engine you prefer type in the search world "Dipole Antenna" and stand back. A dipole is a common antenna with many references.
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Bruce
Senior Member
Username: Bruce
Post Number: 1617
Registered: 9-2003
| | Posted on Friday, September 24, 2004 - 6:40 pm: |
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Try this
http://members.fortunecity.com/xe1bef/dipoles-antennas.htm |
Allagator
Intermediate Member
Username: Allagator
Post Number: 468
Registered: 9-2002
| | Posted on Friday, September 24, 2004 - 7:02 pm: |
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http://www.angelfire.com/mb/amandx/dipole.html
this should give you every thing you need to know about Dipoles !!!! |
Jessejames
Junior Member
Username: Jessejames
Post Number: 31
Registered: 2-2004
| | Posted on Sunday, September 26, 2004 - 1:48 pm: |
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"Thanks" Guys
Happy DXing!! |
Mikefromms
Intermediate Member
Username: Mikefromms
Post Number: 258
Registered: 6-2003
| | Posted on Sunday, October 31, 2004 - 10:18 pm: |
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I have exactly 8' and 6" on each side of my dipole from the end insulator to the middle insulator. The same on both sides. I am using 42 ft of mini 8x coax and have stripped the shield that is wrapped around one side of the wire and the center is wrapped around the other wire and secured with black tape. I have less than a 1:1 match and it is constant even with the amp on. I like dipoles. My dipole is surprisingly broadbanded. At 20' my dipole often can talk skip when my other antenna 73'up in the air won't.
mikefromms |
The ELCO guy (Unregistered Guest)
Unregistered guest
| | Posted on Monday, November 01, 2004 - 7:17 am: |
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Re Mike....
What you are seeing is probably due to the Angle of Radiation. Your signal exits the antenna at an angle. IF this angle and the height the atmosphere is reflecting the signal are just right the signal will bounce off the charged atmosphere and down to the surface of the earth JUST RIGHT.
Might I suggest you build the following antenna. It has a low angle of radiation so local communication pretty well stinks but it is a great distance antenna. Use a standard mirror mount, mount it on a pipe just 6 inches or so off the ground and screw on a 102 inch stainless steel whip. Cut at least 4 lengths of scrap wire (just about any kind will do) 5% longer than the antenna. Attach these pieces of wire as Radials to the mirror mount where the mirror mount and the pipe in the ground are attached and bury them just below the surface of the dirt (not toooooo deep now). Fan out the wires spacing them equally in a circle. Feed the center of the coax to the vertical steel whip and the ground to the radials with 50 ohm coax.
This is a ground mount vertical antenna.
The charastics are as follows....
The Angle of radiation is pretty low with the ground field in place so your first hop skip will be long.
The Local Talking will be limited because it is soooo close to the earth so do not expect too much from locals.
SWRs are usually pretty good and if you need to lengthen the antenna just use a split nut and add a bit of wire to the length of the antenna.
Radials are optional. Radials increase the efficiency of the antenna but you can get by without them. All you have to do is to keep the antenna within 4 to 6 inches off the ground so that a "Natural" ground connection takes place via the metal water pipe.
Materials can vary. If you make your own antenna mount you can use just about anything for the antenna: wire or any kind of pipe. Just try to avoid using anything that rusts if you plan to install the antenna as a permanent fixture. LOL ONE GUY even made such a vertical antenna by welding BEER CANS together. Recycling !
Later
That ELCO Guy
If you have any problems just give me a posting here. |
Stepchild
Intermediate Member
Username: Stepchild
Post Number: 140
Registered: 11-2002
| | Posted on Monday, November 01, 2004 - 1:20 pm: |
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One question.Are the wire dipoles directional?
Stepchild |
That ELCO Guy (Unregistered Guest)
Unregistered guest
| | Posted on Monday, November 01, 2004 - 6:23 pm: |
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Re Steppie...
Yes and no. Yes in that the signal is radiated in figure 8 pattersn beteen the feed point and the length of the wire in at least 4 directions at once.
Having said the above, IF you position your antenna just right one of these lobes of signal will align itself in a desirable direction.
So the answer is both yes and no, kind of :-) |
