RadioBanter - View Single Post

February 28th 04, 11:41 AM

(John) wrote in message . com...
Need a little help here.

I've been using a G5RV for a number of years for my receivers and it
does a very good job. But I notice that many folks here seem to prefer
a long wire. Is there much difference between a long wire compared to
a G5RV or dipole?

Depends...They can be quite the same, "lower bands" or drastically
different, "higher bands" depending on the length of the wire. Also,
you may really mean a "random wire". A true longwire is over one
wavelength or longer. A random wire could be anything...Short, or
long. If it's over one wave long for a certain band, it qualifies as a
true longwire.

And if using a long wi wouldn't a long wire need
to be electrically matched to the receiver?

No. Usually not. It's an option. Overkill for most good receivers.

Or, by using a G5RV, am I
essentially using 1/2 of the antenna as a long wire (the center
portion of the antenna jack on the receiver so to speak).

A G5RV is a center fed 102 ft dipole, fed with a combo of
coax/choke-balun/twin lead.
It was mainly designed as a 20m antenna. For all band use, G5RV
recommended running ladder line and using a tuner. Same as any other
ladder line fed dipole.
The feedline is NOT intended to be part of the antenna. Calling it
back to back inv L's is quite a stretch...Back to back inv L's would
be both fed from the ground. A normal 1/4 wave inv L mainly acts as a
vertical radiator with a horizontal loading wire. Much more radiation
"current" is from the lower vertical section from the base up, than
from the horizontal wire. Feeders of ladder line or twin lead do not
normally radiate, or act as a vertical antenna element when feeding a
dipole. Being they *should* be balanced, the current cancels. Only
common mode problems would cause feedline radiation. And even if it
did, it would be unlikely to have the mainly vertical pattern of an
inv L. IE: max current at the base, etc...It would be about the same
as a coax fed dipole, with no balun used between the balanced dipole
element and the unbalanced coax. If you stick the center pin only ,
yes, it's about like an inv L or random wire fed from the shack. You
may notice MW and real low HF freq's work better this way...

Is one
antenna really that much better than the other?

Just depends on what you are using it for.

As I said, I've been
using a G5RV for quite a long time and I feel I can pick up just about
the same things other folks do; so I don't believe changing to a long
wire would dramatically improve my reception.

You are probably right.

But then again, I might
be wrong.

Nope, I doubt it.

Any help would be appreciated in understanding the
difference between the antennas a bit better -- if there is any.

I prefer center fed dipoles over most random wires because they are
balanced, and it's easier to avoid common mode problems. For
receiving, this usually means a quieter antenna with less shack noise.
They are also complete antennas within themselves, and do not require
a ground, or radials to supply the missing half of the antenna. As far
as pattern, it all depends...Some *real* longwires, IE:
multi-wavelengths long, are quite directional. But even a 10 wave wire
on 28 mhz would have trouble beating my tri band yagi. And the yagi is
rotatable. MK