See comments below.....
.........bc ([EMAIL PROTECTED]
http://www.widomaker.com/~conk
Williamsburg, VA 23185
On Wed, 11 Sep 2002, Monkey King wrote:
> Thanks. Very interesting.
>
> >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.
>
> Why doesn't leaving the antenna down on your Tx damage the Tx then? Is it
> just not enough power?
Well, it can if it's left like this for a very long time. Note, don't use
the tramsmitter with the antenna removed. Also, you may note that the
module heats up when operated with the antenna down. And, yes, it would
be a lot more of a problem if the power was greater. And, I suspect that
the manufacturers have designed in certain measures to insure that the
equipment we buy is overbuilt to stand up to the misuse we subject it to,
>
> Does this imply that the ideal practical volume of an antenna is
> (wavelength x (as big around as you can get it))?
>
I'm not sure, but I think there is a limit to the diameter of an antenna.
I don't think that 'bigger' is necessarily 'better'. ONce the SWR curve
becomes flat over the required range of frequencies, it isn't going to get
any better.
> Obviously, a tube works, because that's what Tx antennae are; would a tube
> 8" in dia. work, thereby reducing interference? Would a flat plate work
> better in one direction than another?
>
Yes a tube works. Infact, RF energy ride on the surface, so a tube of a
given diamter is probably better than a wire of the same diameter. TV and
Radio stations use tubes feedlines and antennae. MOst of your TV rec
antennae are made of tubes. It is lighter and works well. The super high
frequency antennae such as radar etc, use wave guides which are tubes of
various sizes and cross-section to convey RF energy from the tramsmitter
to the airwwaves.
Many high power Radio and tv stations even run some form of coolant thru
the tubes to cool them.
I don't think the flat plate works very well. ANtenna length is the
determining factor in resonance.
> -J
>
>
RCSE-List facilities provided by Model Airplane News. Send "subscribe" and
"unsubscribe" requests to [EMAIL PROTECTED]
