Bruce,
A couple of comments if I may on the web page you included a link to.
These are based upon over 32 years of Beverage use, simplistic observations
to detailed testing.
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
** Ive measured 250-275 Ohms ground resistance here. This is with a 1-2'
covering of rocky and sandy earth over solid rock.....about as poor as you
can get outside of a city. Its almost always moist thru the woods.
Beverage antennas require the bending of radio waves to work. Poor
conductivity earth provides the necessary bending
** The term used is wave tilt and that is what produces the voltage on the
wire. A perfectly vertical wave front such as over sea water would produce
very little voltage. Too much tilt reduces the maximum length.
When obtaining a Beverage antenna transformer, check the earth conductivity
value published for your area. Use a 450 ohm transformer for a more
conductive location. Use a 330/350 ohm transformer for a low conductivity
location. Matching to the transformer will increase the signal to your
radio, but will not change the antenna pattern.
** While a small mismatch is not a problem a substantial one will affect the
F/B.
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
** Antenna impedance is only a few Ohms.
a.. 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.)
** Ive found that to be not the case here where a Beverage runs under
elevated radials with about 6' seperation. One direction picks up crud from
a neighbor and the other points over a few miles of woods and is dead quiet.
The same is stated in the current ON4UN book. Perhaps a sufficient number of
radials are required to shield the Beverage from the vertical.
a.. Take care not to transmit into a Beverage antenna with standard
transformers. If transmit is desired, an antenna tuner can be used in place
of the Beverage transformer. A much higher wattage termination resistor is
needed. (Beverage antennas have negative gains)
** But they can be used to transmit as proven by Belrose and the Canadian
government. Ive made 160 and 80M contacts using 750-1500' Beverages; no DX
but decent US reports. I made my own binocular core transformers from large
43 mix beads of the type that fit over RG-213 and used large non inductive
military surplus resistors at the other end. Ran fine at 100W, cooked some
transformer wire at 1200W in the one test I tried at that power!
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. (Short metal lengths can pick up
signals like AM car radio antennas did years ago)
** If solid rock is in the way drive them in at an angle, Ive even had to do
that for the power line ground. For my particular soil, or lack of, I cut an
8' rod in half, drive at an angle and attach 3-4 30-50' radials to each
fanned out in front. Rods are 15' apart.
Standard (best) wire lengths for a Beverage from the tables available are
290, 440, 600, 800 feet.
** There is no such thing as magic lengths, every installation is different.
With a well established ground reference, a proper termination and an
accurate matching transformer there should be no ideal lengths since the
system is totally nonresonant. Mine are approximately 600, 700, 750 and 900'
and there is no observable difference.
Covered wires may somewhat reduce noise in areas where rain or snow static
are a problem.
** Thats an old myth which I bought into decades ago. Then I installed
parallel 750' wires about 10' apart, one using black jacketed #12 copperweld
rural telephone wire and the other bare #14 stranded copperweld. Absolutely
no difference in a few years of comparisons.
The same with inverted vees using the same materials.
Bare #14 stranded Copperweld Beverages or regular wires in the air did seem
to attract lightning induced (no direct hits) damage more as noted by broken
strands showing molten ends and a relatively short life of 5-6 years. The
telephone wire has been used at 2 locations with some over 32 years old.
For those using individual wires one of the better wire coverings is THHN.
This covering is tough, thin and light. Covered wire results in a slowing of
radio waves known as velocity factor.
** Long proven to be about 3-4% increase in VP.
A given covered wire length will resonate lower in frequency than uncovered
wire.
** Only in a resonant antenna such as a dipole. A Beverage is nonresonant or
anti-resonant for the blokes in the UK, VK, etc
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.
** WD-1A is .10/ft and up thru dealers which isnt exactly cheap when several
thousand feet are needed. I finally scored a NOS 2 km reel for $45. Army
guys can splice it in minutes when the bullets are flying.
Electric fence wire spaced about 6-10 inches (depending upon wire size) has
an impedance about 600 ohms, and is available for about $22.00 for 1/4 mile
at farm supply stores. It splices easliy, and can be soldered with a torch.
** The galvanized steel wire has a finite life in some enviroments and its
RF resistance adds to the wave tilt so total lengths have to be less than
copper before reversal takes place.
The economy route using electric fence wire has an extra benefit. As noted
in "Low Band DXing", early two wire Beverage antennas, often, at the far
end, had one wire insulated and one grounded.
** Which has since been proven as a poor way to do it. For economy in a
small space the Slinky Beverage does very well. Five large ones stretched
over about 175' approximates a full wavelength and are very quiet. VP
computes to .57 which means you dont want to add more Slinkys at least at
that turns pitch.
Close spaced wires gave less signal and front to back ratio than wider
spaced Beverage wires that gave good results without a refelection
transformer.
** Say what?? Close spaced has no effect on signal strength as proven by all
using WD-1A and similar which is about 93 Ohms impedance. Wide spaced loses
the balanced line effect as each wire now has a portion of antenna mode
current.
Plus the close spaced lines naturally twist during install which further
aids balance.
a.. Longer BOG antennas loose signal strength. One that works well on 160
meters, may be lower signal strength on 80 meters and possibly reverse
direction on 40 meters.
** Again that is very ground dependent. My 600' BOG that is on leaves
(actually mostly under the recent fallings)and very low ground cover shows
only a few dB less signal than one at 6'. Buried under the snow for months
last winter had no effect either. I dont use any preamps unless its to make
up bandpass filter loss that are usually switched out except during contests
or when BCB signals are extremely strong.
Installed a 50 to 50 ohm isolation transformer in the BOG antenna coax cable
at the shack end. This solved TV and house noise picked up by the
coax.(Reduction of Common mode pick up)
** With binocular core transformers using sleeves to minimize interwinding
capacitance and proper seperation of antenna and coax grounds is the first
place to start. If there is any pickup on feedlines that are disconnected
from the Beverages there is a problem to be corrected.
The 1:1 isolation transformers shouldnt be necessary unless something is
amiss such as water corroded shields or ground loops.
I use a 750' run on the ground of 1/2" CATV hardline back to the house and
individual antenna feeds are elevated runs of RG-6 quad shield and flooded
and using Thomas & Betts F connectors. Prior attempts at ground runs
resulted in critter destruction. The 1/2" line has been there 22 years.
(One wavelength for 160 meters in free space is 537.4 feet, times the mid
coast Maine .4614 velocity factor for field telephone wire on the ground
equals 247.9 feet). On going research of a 247 foot, two wire, two direction
BOG has ended. Earth freezing caused pattern changes, but found it useable
for many DX contacts.
** How did you determine the VP? It will be interesting to see how my 2 wire
BOG's survive this winters ice age.
Carl
KM1H
----- Original Message -----
From: "Bruce" <k1fz@myfairpoint.net>
To: <topband@contesting.com>
Sent: Friday, November 18, 2011 1:28 PM
Subject: Topband: Bog wire
>I also have found the BOG antenna to be quieter than my up in the air
> Beverages. In some types of thunderstorm QRN I have been able to make DX
> contacts when copy was not possible on other Beverages. Self termination
> varies with ground conditions. Trying to resonate a BOG is like chasing a
> butterfly, as ground conditions are constantly changing. The non resonant
> approach is working well,
> my BOG length is now 160 feet. Low Banders in my area are using from 134
> to 160 foot lengths.
> An earlier experiment with a two wire, two direction 247 foot BOG went
> well
> until late winter when snow melting and re-freezing took place. Then self
> termination, and pattern changes took place. Best length varies with local
> ground conditions and bands of interest.... ( Non-conductive sands of Cape
> Cod, and Florida would be near the BOG optimum)
> They are easy to install, low maintenance, and rarely gets damaged.
> Beverage notes www.qsl.net/k1fz/beveragenotes.html
> 73 Bruce
>
>
>
>> Ive had a single wire 600' BOG for a bit over a year and I must say Im
>> impressed. > Carl
>> KM1H
>
> _______________________________________________
> UR RST IS ... ... ..9 QSB QSB - hw? BK
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>
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