Topband: wire on the ground antenna

[Guy Olinger K2AV]

No, it's not silly.  People have buried BOG's in lawns, although
"burying" the wire is usually just pushing the wire into a slice into
the sod.  The wire needs to be insulated and sealed at the end of
insulation to prevent deterioration (teflon insulated, silver plated
copper wire is available from time to time on eBay and will last).
Use of the tune-it-as-a-DOG at 1140 kHz is required, because sliced
into the sod will fetch you the lowest VF and the greatest variability
of results.

A BOG will generally require an external preamp unless the RX supplies
one for you.  In-pattern gain values of -20 dBi are very common. It is
important to follow procedures to keep feedline common mode current
from ingress at the antennas feedpoint due to the low gain of the
antenna.  There is a good deal of useful information on this subject
in the reflector archives.

You can still model buried BOGs with NEC2.

Approximate your OWN backyard or BOG location (best method) by
creating a DOG tuned at 1140 kHz IN THE POSITION AND DEPTH YOU INTEND
TO USE FOR THE BOG. At the point of zero reactance, 1) measure the
length of the DOG from end to end, and 2) measure the RESISTANCE
portion of the impedance at frequency of ZERO REACTANCE.  This value
may be from 50 to 200 ohms or more depending on the characteristics of
the soil.  Now measure the IMPEDANCE (R +/- X) up and down 50 kHz
(1190 and 1090)

If this soil is normally damp in the 160 season (fall, winter, spring)
and it is dry (e.g. summer), it will be useful to dampen the soil and
let the water soak in first.  The moisture content can cause
significant variation in measured ground constants.

In the model, using the length from the DOG, vary the wire height
anywhere from one wire diameter to several inches, and using "real" or
"high accuracy" ground constants (typical names for Norton-Sommerfield
ground approximation method) vary the ground constants until you get
the same 1140 kHz resonance and zero-reactance resistance, and as
close as you can to the 1090 and 1190 readings.

Use this height and ground constant for your
ground-low-velocity-factor (GLVF) antenna modeling.  You will find you
can model loops, bent antennas, curbside antennas (get new height and
zero X resistance when you move the antenna position).   You MUST
remeasure when you change position.  Things such as ground fill during
construction, septic fields, underground sand strata, yada, yada, have
caused wild MEASURED variation in GLVF X and R readings.  These cannot
be reliably ESTIMATED.  They must be MEASURED as positioned for use.
This one thing is likely 90% responsible for the wild variation and
poor reputation of BOGs.

Once you know these constants you can experiment with buried wires
using a NEC2 program.

For a ground connection do NOT use a NEC2 ground connection.  At each
end start with a pair of 90 degree offset long (200 feet) radials at
the end, AT A HEIGHT OF ONE WIRE DIAMETER.  Put a source on the last
segment of the BOG wire next to the radials and run the model at 1825
kHz displaying the current along the radials.  Lengthen the radials if
you need to until you can clearly see a current maximum. Note the
distance from the end of the radials to the (outermost) current
maximum.  Use this distance as the length for the radials.  Note that
this is particular to your OWN MEASURED GLVF constants, as these wires
will be using the same ground constants as everything else in the
model.  It will vary for every different user and ground composition
situation.  It CANNOT be one GLVF constant set fits all.

Start out your modeling with 225 ohm termination load on the last BOG
wire segment next to the far end radials.  Vary the frequency upward
and watch the pattern reverse.

More detailed discussions on this should probably be removed to the
Antennaware reflector.

73, Guy.

On Fri, Jul 30, 2010 at 1:25 PM, K4SAV <RadioIR at charter.net> wrote:
> Has anyone ever tried a BUG (Beverage under ground)?  No, I'm asking
> seriously.  Maybe just at the grass roots.  I expect you would need a
> good preamp, but that can be done.  NEC2 can't even attempt to analyze
> this.  I know a guy that had a BUL (Beverage under lake) and he liked
> it, but I don't know how well it really worked.
>
> Jerry, K4SAV
>
> k3bu at optimum.net wrote:
>> Uhm,
>> isn't BOG - Beverage On the Ground variety?
>> What you describing is DOG - Dipole On Ground.
>>
>> I used to have BOG run as a long Beverage wire, mostly unterminated, just laying on the ground, or tucked along the curb of the asphalt road.
>>
>> Another version was LOP - Loop On Ground. Originally intended as a electric dog fence around the property, about 460ft loop, burried about 1" in ground. By the time I put it down, dog got smart and did not need it. So I put 600 ohm transformer on it between the ends and VO1LA - it worked and heard what Inv Vee could not. Seemed to be non band discriminatory.
>>
>> For stealth BIT Beverage In Toilet, one can flush the tennis ball with wire attached to it down the toilet and have the underground one.
>>
>> 73  Yuri  K3BU.us
>>
>>
>
>
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