[Antennas] question regarding dipole

2002年3月18日 16:49:10 -0800

I like the general trend of this thread.
I surfed upon a site that mentioned the use of coax for a vertical, as the 
velocity factor shortened the antenna, then he went on to bend the 
antenna. Apparently, the coax shortened ant was a vertical 1/4 wave but 
could be used as a 1/2 wave. Any one know the URL of said?
Next, from my readings the use of a 'thicker' radiator shortens the 
dipole. Tubes or cages.
But folding the wire lengthens the wire required. Read about "Z", "W", 
linear loaded, folded back, etc antennas.
I forget how to prove it, (it requres trig and calculus) but the 50% of 
the radiation comes from 16% of the centre of the dipole. The rest of the 
dipole is to make the proper resonance.
Please let me know how you make out.
Chris opr VE7HCB
At 04:50 PM 2002年03月18日 -0600, Bob Wilder wrote:
>Two questions: 1] how much room do you have? 2] Do you plan on using a tuner?
>Think about building the who thing out of 450 Ohm ladder line with 4:1
>Balun at center
>to 450 Ohm line...See My web site for antenna I use under CURRENT...works
>great
>with 100 watts on 40 meters.
>>>>At 05:25 PM 03/18/2002 -0500, Joe Falcone wrote:
> >Hello: I want to run a dipole for 40 meters, 33 feet for each leg, under
>my second story deck. I was going to use insulated wire and staple the
>wire to the underside of
> >the
> >supports of the deck. Purpose of the antenna is just to hook up to when I
>am on the deck to work some 100 watt CW.
> >
> >I am going to fit the 66 feet of dipole into 40 feet by simply running the
>wire in a pattern like this _|~~|__|~~|________ center
>__________|~~|__|~~|__ You get the
> >picture. (I made the top lines wavy only because I did not know how to
>type them straight. The wire will run in straight lines).
> >
> >My question is: Is there some type of rough rule of thumb on changing the
>lenght of the wire if you are going to shorten the total lenght of the
>area that the dipole is going
> >to fit into, or doesn't it matter? Would I still use the 33 feet? This
>antenna will be up about 8 feet from the ground, but the land slopes away
>from the house.
> >
> >Thanks, Joe. N8TI
> >
> >
> >- - -
> >
> >Your moderator for this list is:
> >Larry Wilson KE1HZ [email protected]
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>>73
>Bob Wilder, AF2HD / AFA2HD(USAF MARS)
>TSgt, USAF (Retired)
>6032 Idlemoore Court
>Theodore, Alabama 36582-4036
>(251)653-5274
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