OK.
SWR is short for Standing Wave Ratio. Which is the ratio of forward to
reflected power in an antenna system, and affects the efficiency of the
antenna.
Ideally, a tranmitter will dump it's output into an antenna and it is
radiated out to the world. The length of an antenna is dependant on the
frequency, and thus the wave length or lenght of one cycle of the RF
signal. When an antenna is cut for the exact length for a given
frequency, the SWR will be very low (ideal is 1:1). This condition is
called resonance. If the antenna is longer or shorter, the SWR will rise
and the radiated power will be less. If it gets too far from resonance,
it can cause damage to the transmitter output stage. If you graph the
SWR vs frequency, you will see a dip at resonance. A very small diamter
antenna will have a sharper dip than one of considerably larger diameter.
I have a 2 meter antenna for my car made of .093 wire, and it has a fairly
broad SWR curve, nearly flat over the 4 mHz wide 2-meter amateur band.
At 72 mHz, we need only cover slightly less than 1 mHz, effect is almost
none.
And, yes, I have been refferring to transmitters here but receivers
antennae follow the same laws of physics.
.........bc ([EMAIL PROTECTED]
http://www.widomaker.com/~conk
Williamsburg, VA 23185
On Wed, 11 Sep 2002, Monkey King wrote:
> On Wed, 11 Sep 2002, Bill Conkling wrote:
>
> >Answer: Yes and no....
> >
> >In our world of R/C modeling, the diameter of the antenna wire matters
> >little. But, in theory, a larger diameter wire will have a more constant
> >SWR over a given frequency spread.
>
> If someone doesn't know about the effect of the diameter of an antenna is,
> that person also probably doesn't know what SWR is.
>
> Me, for example.
>
> -J
>
> >
> >.........bc ([EMAIL PROTECTED]
> >
> > http://www.widomaker.com/~conk
> >Williamsburg, VA 23185
> >
> >
> >On Tue, 10 Sep 2002, Bill Johns wrote:
> >
> >> Greetings!
> >>
> >> Does the diameter of the Rx antenna wire matter? If you use a very thin
> >> wire do you loose range or sensitivity?
> >>
> >> Just curious.
> >>
> >> Thanks,
> >>
> >> Bill
> >>
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