Beverage antennas
One
wire configuration notes
- Best to
use separate ground rods, as sharing can cause signal coupling through the
connection.
- Copper
coating on steel ground rods erodes with time. Recommend the use of thick wall
copper pipe, available in most hardware stores.
- Break
away ties/fastenings improve wire survival from falling limbs, and trees.
40 to 50 pound monofilament fish line works well.
- Keep
Beverage wire ends away from towers that can re-radiate signals even if
they are not used as transmit verticals.
- Woods,
trees, and vegetation, represent only minimal signal loss reported over
many years. In one wooded area, a low to the ground Beverage at my QTH is
under the snow much of the winter, and works fine.
- Maintain
a reasonable constant height above ground except at the ends that may be
tapered to ground level. Follow the general contour of the earth, but not
every small dip or bump.
- Beverage
antennas "want to work". For best results run a straight line.
If a straight run can not be maintained, good results can be obtained with
less than perfect.
- If the
Beverage is being used as a single direction terminated antenna, the
termination resistance is controlled more by ground conductivity, than
wire height. A poor conductivity earth termination would typically be 350
ohms or lower. A more conductive earth termination would typically be 450
ohms or higher.
- When
choosing a termination resistance, avoid the one that gives the minimum
VSWR on the band of interest, rather choose the
resistance that gives the lowest VSWR over a wide frequency range with a
slow increase at the highest frequency end. You may end up with a 1.8:1
VSWR, but you will have found the characteristic impedance of the wire
resulting in the best antenna front to back ratio. (The 1.8:1 VSWR would
be most likely from a matching transformer to antenna impedance
difference)
- Beverage
antennas require the bending of radio waves to work. Lower frequency radio
waves bend around mountains, into valleys, and have deeper earth
penetration. Poor conductivity earth helps provide earth penetration, and
the necessary bending. (Often called tilt angle)
- If you
are near the sea, running the Beverage antenna along the beach may result
in a antenna that does not work as well. You
could arrange your Beverage so it starts or ends up near the waters edge
to get a good ground to receive those low angle signals that tend to
follow sea water.
- Beverage antennas are low impedance, low
Q devices, and do not couple well. Beverage runs can cross each other if a
few feet of clearance is allowed.
- Radial
fields radiate energy from the connected vertical. Avoid running a receive
antenna, or receive coax across one. (Raised radials radiate more signal
energy than in ground radials.)
- There
have problems reported using heat shrink on termination resistors, and
multiple reports saying no protective covering is necessary.
Two
wire, two direction Beverage notes
- When
using individual wires, maintain the spacing between the two wires. This
will help the front to side signal ratio to be near optimum. Treating the
wire spacing like a transmission line will help the forward and reverse
signal levels to be more equal with proper transformers.
- Slope
the wires down to ground at both ends?
Tried this at my locations, and at a friends
QTH. We found the slope did not change low angle vertical signal levels
compared to a straight drop. We did find that unwanted high angle signals
were reduced with longer slopes. Manufactured transformers are usually are
wound for ~450 ohm impedance to ground. Wire height at the Beverage ends
effects impedance thus the terminating resistance (impedance) and pattern.
(Use public safety when using low wires)
- In
Northern climates use a long ground rod as winter time frozen earth does
not conduct well. If it is not possible to drive a rod all the way in,
avoid leaving a large amount above the ground. (Length may increase pick
up of nearby strong AM radio station signals) Mixing, birdies are
possible. (But also, cut the excess off for human safety)
- The coax
outer shield can pick up signals and compromise the front to back. It is
good to have the last 60 or more feet of coax buried near the Beverage box
to reduce unwanted signals. In cases where the coax is above ground, an
effort should be taken to remove common mode signal pick up.
- Termination
of un-used coax is not necessary with accurately placed transformer coil
center taps. The two wire Beverage system is a RF version of the old
telephone simplex circuit of the 1930's. (Two talk circuits could take
place on the same wire pair with electrically center tapped transformers
at each end, without cross talk.)
- Covered
wire results in a slowing of radio waves known as velocity factor. A given
covered wire length will resonate lower in frequency than uncovered wire.
- Many
find 9 feet above the ground is a good compromise height. (Crossing a
roadway not included)
- I have a
close to the ground Beverage antenna in an out of the way area. The
pattern and signal to noise ratio are excellent. QRN sometimes noted in
solar storms is often less than with taller Beverage antennas. At 2 feet
above ground found a pre-amplifier to be unnecessary
- Much of
the expense of a two wire Beverage is the cost of the wire, and upkeep.
450 ohm cable expense is high, and breakage repair is difficult. WD-1 wire
is inexpensive, but repair is somewhat difficult.(Steel
strands send me looking for band aids) Both types can deteriorate if water
penetrates the insulation. Galvanized electric fence wire spaced about 4-6
inches has an impedance about 600 ohms (depending upon wire size), and is
available for about $22.00 for 1/4 mile at farm supply stores. A Western Union splice works well in case of breakage.
- In the
past, tried a 680 ohm two wire Beverage antennas using electric fence wire
spaced horizontally, than vertically. No reception difference noted. Found
vertical spaced runs easier with out the need of cross arms.
- Increased
common mode decoupling of the coax cable was often accomplished by addng a coil of many coax turns, combined with added
ground rods.. As time passed the number of turns were reduced by adding ferrite cores.
Now a popular choke is constructed by winding 6-8 turns of small diameter
coax in a 6 inch diameter coil and held together with plastic ties. One
mix 31 ferrite 'clamp on' core Amidon 2x31-1081P2, or equivalent is installed over the
windings. For increased attenuation use more turns.
- Propagation
note: On 160, look for the auroras. Early after they strike the energy
goes to the Earth's poles. At that time, depending upon location, they can
give great extended DX, and spotlight propagation.
- I have
noticed after many meteor showers that long propagation on the low bands,
especially 160 meters, is very poor or non-existent.
QRZ
call search
FO0AAA receiving Delta loop. K6SE & ON4UN eham 806.
IV3PRK BOG/WOG antenna
research
Signal Propagation
QTH.com Free Ham Radio Clasifieds
K1FZ (Bruce Clark) Background highlights:
Worked in the late 1950's to early 1970's for WLBZ-TV Bangor, Maine as a
transmitter engineer.
Most interesting employment: Worked as the senior maintenance engineer for the
Christian Science Monitor syndicate short wave AM radio station in Maine. Transmitter power
output was 500 KW. Two high gain TCI model 611 4X4 slewable
curtain arrays, topping 363 feet AGL, gave a ERP power
of 5 megawatts. (ERP Varied with frequency in use)
Recently retired from WERU-FM 89.9
MHZ. I listen on line
at www.weru.org , a
PBS Community Radio FM broadcast station. Music, programs vary with day, and
time of day. My favorite is Jazz music 6-8PM weekdays eastern time zone.
73
Bruce
[email protected]