antennas

[Shaun Oliver]

Hi all, at the moment, I have a piece of wire running straight into the
back of my radio as an antenna.
assuming I have my lengths and what all right, could I not use this here
piece of wire to tx?
or, am I running the risk of exposing myself to more rf than perhaps I
should?
I'm seriously considering an NVIS setup for 40 and 80 meters but, I need
to be careful in that regard also as the reflector element for such an
antenna would be aproximately 44.2 meters which is roughly the length of
the block from boundary to back fence.
could I not rig up a quarter wave length of wire and reflector and use
it for a similar setup or does it absolutely positively have to be half
wave?
thanks in advance.

--
Shaun
web sites:
http://www.myspace.com/blindmanshaunoliver
http://blindman.homelinux.org/~blindman/
skype: brailledude
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[Don Wilhelm-4]

Shaun,

It all depends on your entire NVIS antenna system.  A quarterwave
radiating element needs another quarter wave wire as a 'radial' or
'counterpoise' (the quotes are intentional).  So, you end up with a
total of 1/2 wavelength in any case.

Why are you concerned about a reflector for an NVIS antenna - the earth
itself can serve as a reflector.  A dipole on 80 will be longer than
your available space, but then it can be bent drastically and still
perform quite well.  For NVIS, try a regular dipole mounted 10 to 15
feet above the ground - check it with an antenna analyzer that trim to a
resonant length.  Even though it may have to bend substantially, it
should work fine once tuned to resonance.  For 2 band use, use a
separate radiator length for each band and run the two antennas at right
angles (or as close to right angles as your physical constraints
require) to each other - feed the center with a common feedline and use
it - it may not be ideal, but it should work for you.

73,
Don W3FPR

Shaun Oliver wrote:

> Hi all, at the moment, I have a piece of wire running straight into
> the back of my radio as an antenna.
> assuming I have my lengths and what all right, could I not use this
> here piece of wire to tx?
> or, am I running the risk of exposing myself to more rf than perhaps I
> should?
> I'm seriously considering an NVIS setup for 40 and 80 meters but, I
> need to be careful in that regard also as the reflector element for
> such an antenna would be aproximately 44.2 meters which is roughly the
> length of the block from boundary to back fence.
> could I not rig up a quarter wave length of wire and reflector and use
> it for a similar setup or does it absolutely positively have to be
> half wave?
> thanks in advance.
>

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