| Author |
Message |
    
Ncrebel
| | Posted on Wednesday, June 26, 2002 - 1:22 pm: | 
|
Ok,you know how if you make a dipole antenna out of wire that it has to be like a little over 17
inches long.Can't quite remember the exact correct
length.But anyway,when you make one of these antenna can't the antenna be curved in anyway or does each end have to be around 17 inches apart
(antenna completely stretched out)??This is
something I've been thinking about because in some places you see how people advertise
"no-ground mobile antenna".The only way to do this is have a 1/2 wave antenna?So how do they make a 1/2 wave antenna thats not around 17 inches long?Thanks for your help. |
Phineas
| | Posted on Wednesday, June 26, 2002 - 2:06 pm: |
|
In what band? 1/2 wave in CB is 18 feet long. Stretched out is the best way to mount a Dipole, but I have done Vs, Inverted Vs, L shape, Etc.... Different shapes mostly effect you reception for transmit and receive, and may need to be retuned some. Due to the slight added Inductance. |
bruce
| | Posted on Thursday, June 27, 2002 - 5:37 am: |
|
a quick way length= 468/27 = 17.33 foot or 204 in |
Ncrebel
| | Posted on Thursday, June 27, 2002 - 11:30 am: |
|
Okay then,thanks for your reply.I didn't know if it could be coiled or anything like that. |
DeadlyEyes
| | Posted on Thursday, June 27, 2002 - 6:41 pm: |
|
RE N
The length of a dipole leg is simple to remember. It is the 1234 rule. Or 1 quarter wave leg length equals 234 divided by the frequency in Mhz.
The length of an antenna can be shortened by loading coils that trick the radio into seeing about 50 ohms.
If you put up a dipole using a 50 ohm coax the best SWR you will get will be 1.5:1 because the resistance of a dipole properly constructed and properly elevated is about 75 ohms not 50 ohms.
BUT you can change the resistance at the feed point of the dipole if you support the center angle the legs of the antenna downward. Play with the angle to get the best SWR. This antenna is called an "Inverted V" antenna and is omni directional. |
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