Topband: Beverages

[Tom Rauch]

 None of us know what the soil really is like since it is
almost impossible to measure.  The method that appears in
books using a light bulb to measure ground resistance is
useless for RF. You might just as well throw a dart at a
dartboard marked in conductivity. The charts in BC
measurements are wide very area averages, so they don't mean
much about a particular spot.

I guess we could build low dipoles and measure impedances
and move them around the area, but mostly we just guess or
assume the soil is "something" no matter what we use as a
base data. That's why making a big science based on
conductivity data is a waste of time.

But let's play that game...

I probably had what is considered very poor soil in Rockdale
county. It was among the worse in the country on average.
Much rock and dry clay. My antennas worked fine, they had
good F/B ratio. My Beverages over wet black loam soil also
worked fine. Good F/B ratio. Same here over clay, same in
Ohio over clay. Same over sand. Still worked fine, still
good F/B.

> I have tried beverages ranging from 40 - 400 mtrs over
poor soil.They have been from 0,5 to 1,5 mtrs up. What
strikes me is that SM6DOI:s beverages perform much better
than mine did although they were exactly the same. (SM6DOI
has very good ground). The antennas were very properly built
by the books. I compared them with my xmitting antenna (2
phased vericals) but the beverage did not work better than
the xmitting array.

What do we mean by " perform better"?  S/N ratio? Where does
the noise come from at each location? Every location I have
receives differently, but I've never had an antenna "not
work".  Receiving antennas sort signals from noise only by
pattern. To be a better receiving antenna, it has to focus
more on the direction of signal than noise. With vertical
antennas anything vertically polarized that has strong
re-radiated signal levels within a wavelength can have
considerable influence on the pattern. Beverages are
vertically polarized, and while they don't re-radiate much s
ignal to bother other antennas they are as susceptable to
signals re-radiated from other antennas as any other
vertical would be.

What is a good installation? One Beverage handbook has many
installation mistakes. Was the antenna away from other
things? Was the feedline isolated? Did you have good grounds
on the feedpoint? Were there other towers around it? Was the
local noise in the direction of a lobe of the beverage, and
a null of the verticals?

> Have anybody, living in poor soil country, tried to lay
out one ore more ground wires simulating a "better" ground?
I haven´t, but plan to do so soon. I bet it will work
better.

Why would that happen?  They quit working over salt water,
we know that. We know that over very poor soil they work
quite well, except in a few cases. Any antenna can not work
in some special case if it is not in the clear, and any
receiving antenna can not work if something nearby is
bothering it or if the noise is not in a null and the signal
in a peak.

A Beverage works only because the earth below the Beverage
has attenuation with distance. There are two conditions
where the ground is not lossy. One is where the ground is
like a nearly perfect insulator, the other is where the
ground is very high conductivity.... like a good conductive
sheet or saltwater.

Wire laid under the antenna can quickly convert zero
conductivity to perfect and change your Beverage to a very
long loop antenna with the vertical ends having all the
response, but it can't help it to be in between which is
where we want it.

I would just be sure something else is not wrong first. If
nothing else is wrong, try the wire with no other changes
and tell us what happens. I bet it gets worse.

73 Tom