[Elecraft] Re:Alligators and Bats

Fri Jan 11 04:48:00 2002

Hi, Ron...

As I told Lou, off the reflector, I misspoke on the gain... of course, a
dipole is 2.14db ABOVE an isotropic source.  My book, by the way, is a 1984
edition which doesn't have a page 20.3... only goes to "16-8".  I believe
there are so many factors to argue on this subject in terms of directivity,
pattern
lobes, distances, propagation, etc., that it's not practical or appropriate
to pursue it on this reflector.

I'm not an engineer and definitely shouldn't get into technical discussions
on subjects like antenna gain or I'll just show my ignorance (even further).
Most of what I know about radio -and antennas- I have learned from
experience, from trial and error, and from older/wiser hams, during
50-1/2 years of hamming.

My reason for posting in the first place was that Lou seemed pretty much
down on verticals and my point was to defend them to some degree.  I would
hate to see beginners dissuaded from trying verticals without hearing an
opposing opinion.  In my experience, A     GOOD     vertical over a     GOOD
GROUND SYSTEM     (salt water not required) does an excellent job!  A
single vertical certainly won't compete with a multi-element array
but, at greater distances, mine has frequently equaled or out performed
dipoles.

Example:  I have a 40-meter dipole, approximately 1/4-wave above ground,
(used to have one up 1/2-wave with very little difference noted)
more or less broadside east and west and a Hy-Gain Hy-Tower vertical.  Every
Sunday for the past eight years, I have talked to friends back in Texas...
about 500 air miles from me, almost directly East.  In all that time I can
count the Sundays on one hand, that the Hy-Tower has failed to outperform
the dipole by one to two S-units, both on receive and transmit, no matter if
the guys on the other end are vertically or horizontally polarized.  The
vertical is rarely noisier and frequently quieter on receive.  That's
another myth -- verticals being inherently noisy.

That said... for communications over 100-200 miles, like within my state,
the vertical sucks... always +/-20dB below the dipole.  And that's the only
reason I have the dipole.

Re: theory... I read somewhere, 40 years ago, that according to the laws of
physics, a bumble bee can't fly.  Theory is valuable but what we're all
after is real-world results.

Sorry for the bandwidth on this reflector but I have had outstanding
results, US and DX, with my K2 running 5-10 watts into the Hy-Tower.  This
one trapless, 51-ft. tall antenna works 80, 40, 20, 15 and 10 meters, and
with the K2's tuner, the WARC bands.  It's a lot more work to put in a
GOOD vertical system than to hang up a dipole.  Mine has three 8' ground
rods (pounded thru rock!), 45 radials under it and is fed with the lowest
loss flexible Belden coax available.

If you aren't willing to invest the time and considerable effort to do it
right,
you may well be better off with a dipole

73.... Ed, W5EJ

----- Original Message -----
From: "Ron D' Eau Claire" <[email protected]>
To: <[email protected]>
Sent: Thursday, January 10, 2002 4:35 PM
Subject: RE: [Elecraft] Re:Alligators and Bats

> Ed, W5EJ, wrote:
>
> > *My* (ARRL) Antenna book says the gain of a real-world dipole is 2.14dB
> > below an isotropic source.  I don't recall any discussions about
> > dipoles in
> > free space, so can't comment on your 8 and ~6dB figures.  But all of the
> > gain figures I remember seeing were either based on an isotropic source,
> > which can raise unrealistic expectations among amateurs, or a real-world
> > dipole.
>
> Gee. Which Antenna book do you have Ed?
>
> My ARRL Handbook ('99) shows (on page 20.3) a predicted gain for a dipole
> 1/2 wave above "average" ground (5 mS/m conductivity) having a gain of 7.5
> dbi at an elevation angle of 26 degrees. By comparison, a vertical over
the
> same ground has just 0 dbi "gain" - more than 7 db below the dipole in any
> terms. The angle of maximum radiation of the vertical is the same too -
just
> on 25 degrees - thanks to the attenuation of the lower angles by the lossy
> earth.
>
> Put the vertical over sea water and it is better - only about 1 db below a
> dipole at 1/2 wavelength over 'average ground'. Of course, a dipole over
sea
> water has better gain from lower ground losses too.
>
> That's consistent with my ARRL Antenna books among other references, and
> with the models I have done using EZNEC of both vertical and horizontal
> antennas.
>
> In general, the vertical will do a better job at low angles (about 20
> degrees) if the horizontal can't be raised at least 3/8 of a wavelength
> above the ground. Of course, a low horizontal antenna will act as a cloud
> warmer providing a lot more high angle radiation for close-in 'skip' than
> the vertical under any conditions.
>
> No slings or arrows, Ed, just a lot of various references that say the
> dipole is better for DX unless you can't get it up in the air.
>
> Of course a vertical will beat a horizontal antenna where you don't have
> room to get at least 1/4 wave of "flat top" up in the air or you are only
> interested in DX.
>
> So I am genuinely interested in the contrary information you have
uncovered!
>
> Ron AC7AC
> K2 # 1289
>
>
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