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Path: utzoo!linus!decvax!ucbvax!ucdavis!lll-crg!seismo!brl-tgr!tgr!YOUNG@MARLBORO.DEC.COM
From: YOUNG@MARLBORO.DEC.COM
Newsgroups: net.ham-radio
Subject: Re: beverages
Message-ID: <2218@brl-tgr.ARPA>
Date: Thu, 17-Oct-85 12:22:15 EDT
Article-I.D.: brl-tgr.2218
Posted: Thu Oct 17 12:22:15 1985
Date-Received: Sun, 20-Oct-85 07:14:15 EDT
Sender: news@brl-tgr.ARPA
Lines: 53

A Beverage antenna (named after a person, not a soft drink) is a directional
receiving antenna.  In it's simplest form it looks like this:

           ------------------- // ---------------------
           |                                          |
         ---                                          \
    Coax                                              / Terminating
         ---                                          \ Resistor
           |                                          /
           |                                          |
         -----                                      -----
          ---                                        ---
           -                                          -

It's input impedance is usually around 300-500 ohms, so a 4:1 transformer
is often used to connect to the coax.  The wire is not very high; 3 to 10
feet is typical.  A good beverage is long.  A half wavelength is considered
short, a wavelength is probably about the minimum where it is worthwhile
to install one.  I know of some beverages for 80 and 160 which are 1500 feet
long or more!

The directivity is in the direction of the resistor.  For the antenna
pictured above, it is like this:

                                           \
                                            \
                   ==========================>
                                            /
                                           /

The resistor is usually about 470 ohms, although the exact value for best
front to back depends on height, length, and ground conductivity.  Some
people use a potentiometer and adjust it for best results.

The antenna has loss as compared to a dipole, so it is never used as a
transmitting antenna.  Many radios require an external preamp when used
with a beverage.  Because the directivity of the beverage cuts down on
the noise (remember, for receiving it's not signal strength, but signal
to noise ratio that's important) it is possible to copy signals on a
beverage which cannot be heard on a dipole or vertical.

Beverages are seldom used above 40 meters, since stations big enough to
justify beverages have directive antennas on the higher bands.  Even
on 40 meters, they are not tremendously popular.  But on 80 and 160,
I have not heard anything which works as well.

There are people who use unterminated beverages, which are bidirectional,
and there are designs for 2 wire beverages where the directivity is
steerable.  But when most people refer to a beverage, they are talking
about the simple 1 wire terminated antenna.

			Paul Young, K1XM
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