What kind of "ground" should I use to EZNEC-model a flat-top dipole antenna
of which one side will be about 7 feet above and parallel to the peak of
my house roof and the other half will be about 30 feet above the yard.

My house is a story-and-a-half (the usual attic was a dormitory for my
long-gone kids) over a full basement (which just happens to have both
a Ufer ground in the basement-wall footings and a "ring ground" around
the outside and at the level of the footings). Thus most of one-half
of the antenna will be over the usual Kansas soil (about a foot of fertile
stuff above many feet of more clay-like stuff) while the other half will
be above the roof above the attic/dormitory above the ground floor above
the basement above the footings.

So will this be a "good", "bad", "average", or ??? ground for EZNEC-
modeling purposes?
--
--Myron A. Calhoun.
Five boxes preserve our freedoms: soap, ballot, witness, jury, and cartridge
PhD EE (retired). "Barbershop" tenor. CDL(PTXS). W0PBV. (785) 539-4448
NRA Life Member and Certified Instructor (Home Firearm Safety, Rifle, Pistol)

Just call it "poor" ground. But try them all.

My guess is that it will make very little difference in performance as
calculated by EZNEC whatever you call it.

Horizontal or sloping dipoles are insenstive to what's underneath
them. Radiating efficiency will be in the right ballpark.

The structure, position and height of your house will have a much
greater but indeterminate effect on radiation pattern and you cannot
model your house using EZNEC. Even nearby neighbor's houses will have
some effect. But you will never know what these effects are compared
with the ideal pattern as presented by EZNEC.

Antenna height above what's underneath is the most important
parameter.

In all probability, you will get around and about very well. Many
amateurs do very nicely with even more peculiar antenna systems.
----
Reg.

=====================================

wrote in message
...
What kind of "ground" should I use to EZNEC-model a flat-top dipole
antenna
of which one side will be about 7 feet above and parallel to the
peak of
my house roof and the other half will be about 30 feet above the
yard.

My house is a story-and-a-half (the usual attic was a dormitory for
my
long-gone kids) over a full basement (which just happens to have
both
a Ufer ground in the basement-wall footings and a "ring ground"
around
the outside and at the level of the footings). Thus most of
one-half
of the antenna will be over the usual Kansas soil (about a foot of
fertile
stuff above many feet of more clay-like stuff) while the other half
will
be above the roof above the attic/dormitory above the ground floor
above
the basement above the footings.

So will this be a "good", "bad", "average", or ??? ground for EZNEC-
modeling purposes?
--
--Myron A. Calhoun.
Five boxes preserve our freedoms: soap, ballot, witness, jury, and
cartridge
PhD EE (retired). "Barbershop" tenor. CDL(PTXS). W0PBV. (785)
539-4448
NRA Life Member and Certified Instructor (Home Firearm Safety,
Rifle, Pistol)

wrote:
What kind of "ground" should I use to EZNEC-model a flat-top dipole antenna
of which one side will be about 7 feet above and parallel to the peak of
my house roof and the other half will be about 30 feet above the yard.

My house is a story-and-a-half (the usual attic was a dormitory for my
long-gone kids) over a full basement (which just happens to have both
a Ufer ground in the basement-wall footings and a "ring ground" around
the outside and at the level of the footings). Thus most of one-half
of the antenna will be over the usual Kansas soil (about a foot of fertile
stuff above many feet of more clay-like stuff) while the other half will
be above the roof above the attic/dormitory above the ground floor above
the basement above the footings.

So will this be a "good", "bad", "average", or ??? ground for EZNEC-
modeling purposes?

The short answer is that it doesn't matter.

I do recommend using "Real, High Accuracy" ground for all models unless
it's necessary to make a zero-resistance connection to the ground plane.

When using "high accuracy" ground, the ground quality is used by the
program for two purposes: 1. To determine the antenna impedance and
currents, and 2. To calculate the pattern, which depends on ground
reflections. The former doesn't make much difference if the antenna is
more than about 0.1 or 0.2 wavelength high. The latter takes place
(except for very high angle signals) well beyond your house or other
nearby objects, and for horizontally polarized antennas doesn't make
much difference anyway (again except for high angle signals).

Whatever effect your house will have on the antenna, you won't be able
to effectively model it. It will be chiefly due to the conductors in the
house -- wiring, pipes, rain gutters, etc. -- and it's just about
impossible to know enough about them to model them decently.
Fortunately, they're unlikely to have much of an effect unless something
happens to be nearly self-resonant. If that happens, you're likely to
know about it via other means (e.g., TVI or other RFI, "hot" conductors
or appliances when transmitting, or even lights that go on when you
transmit), and will be wanting to spoil the resonance rather than simply
modeling the offending conductor.

Roy Lewallen, W7EL

Many years back I once had a 10m dipole about 8 feet from the house at
cast-iron roof-gutter level. The Tx was in an upstairs bedroom. The
short coaxial line to the dipole went through a hole in the bedroom
wooden window frame.

Sunspots were at their best. On completion of the installation, much
to my surprise, I worked my very first Australian (in the antipodes
from Birmingham) and completed the log entry in exceptionally neat
handwriting.

I then went downstairs and reported my conversation with Bill in
Adelaide to my XYL. All she had to say was a brief "Your dinner's gone
cold.". So much for her deflating enthusiasm!

But the most extrordinary thing about the episode was the fact that
the bedroom 60-watt light bulb (admittedly a temporary arrangement)
came on more strongly when the key was UP and went more dim when the
key was DOWN.

I was running 100 watts from a Kenwood TS-520. The bedroom light was
not being run from the 240-volt power wiring to the TS-520. After
years of thinking about it, I have never found an entirely
satisfactory explanation.
----
Reg, G4FGQ

Reg Edwards wrote:
Many years back I once had a 10m dipole about 8 feet from the house at
cast-iron roof-gutter level. The Tx was in an upstairs bedroom. The
short coaxial line to the dipole went through a hole in the bedroom
wooden window frame.

Sunspots were at their best. On completion of the installation, much
to my surprise, I worked my very first Australian (in the antipodes
from Birmingham) and completed the log entry in exceptionally neat
handwriting.

I then went downstairs and reported my conversation with Bill in
Adelaide to my XYL. All she had to say was a brief "Your dinner's gone
cold.". So much for her deflating enthusiasm!

But the most extrordinary thing about the episode was the fact that
the bedroom 60-watt light bulb (admittedly a temporary arrangement)
came on more strongly when the key was UP and went more dim when the
key was DOWN.

I was running 100 watts from a Kenwood TS-520. The bedroom light was
not being run from the 240-volt power wiring to the TS-520. After
years of thinking about it, I have never found an entirely
satisfactory explanation.
----
Reg, G4FGQ


Reg;

Reminds me of my first contact using an 11 meter J-pole antenna that I
made. It was only about 40 miles using 5 watts input AM. Not much by
your achievement but to me at the time I thought it was wonderful.

As to you lamp dimming, I do not know what the wiring capacity of you
house was but the transmitter was being fed by the same mains drop from
the street as the lamp. That is, IMO, the most likely cause of the
dimming. Just my guess.

Dave WD9BDZ

As to you lamp dimming, I do not know what the wiring capacity of
your
house was but the transmitter was being fed by the same mains drop
from
the street as the lamp. That is, IMO, the most likely cause of the
dimming. Just my guess.

Dave WD9BDZ

=======================================
Dave,

The mains supply from the road was capable of 50 kilowatts without
excessive volts drop. For a few years it was used for electric
cookers, several 3-bar central heating radiators, etc., without
problems. Far more than the TS-520 with an RF power output of 100
watts.

There may been something very peculiar with the 60-watt bedroom
filament lamp which caused it to cool off when both RF plus 50Hz power
currents flowed through it. I didn't try another bulb.

There may have been incorrect house wiring such that the only power
point in the bedroom, used for the transmitter, was connected, by
mistake, to the lighting circuit. But even then, the lighting circuit
should have been capable of withstanding the load of the transmitter
without much of a voltage drop. Shortly afterwards I moved the shack
downstairs into the garage. At the time I never checked house wiring
and later on the family sold the house and moved. The new owner was
not a radio amateur.
----
Reg, G4FGQ.

In article ,
Reg Edwards g4fgq,regp@ZZZbtinternet,com wrote:

There may have been incorrect house wiring such that the only power
point in the bedroom, used for the transmitter, was connected, by
mistake, to the lighting circuit.

That would be my guess. Here in the US, at least, it's quite common
for a single 15- or 20-ampere circuit to be used for both wall
outlets, and lighting circuits, in one or more rooms. There's nothing
in the electrical code which requires separation of these sorts of
loads... and in fact I seem to recall a clause which actually forbids
"one outlet per circuit" branches, for some reason.

But even then, the lighting circuit
should have been capable of withstanding the load of the transmitter
without much of a voltage drop.

It doesn't take all that much of a drop in voltage to result in a
visible change in the brightness of an incandescent-filament light.
According to one site I've found, light output is roughly proportional
to the voltage raised to a power between 3.1 and 3.4. A 5% drop in
voltage would thus result in a decrease in light level of more than
15%, which would be pretty easy to notice.

If you were transmitting 100 watts CW key-down, I'd guess that your
transmitter was probably drawing at least 300 watts from the
mains, and perhaps rather more depending on its design.

Add a few more likely or possible elements e.g. a linear power supply
which tends to draw most of its current from the mains during the
voltage peaks (and thus causes a disproportionate amount of voltage
sag on the lines during those peaks), insufficiently-thick house
wiring in the walls, and perhaps a slightly loose or corroded
connection to one of the outlets or switches or breakers, and I can
well believe that keying a 100-watt CW transmitter could cause enough
voltage drop to result in visible dimming of the lamp bulb.

--
Dave Platt AE6EO
Hosting the Jade Warrior home page: http://www.radagast.org/jade-warrior
I do _not_ wish to receive unsolicited commercial email, and I will
boycott any company which has the gall to send me such ads!

On Fri, 18 Nov 2005 19:02:31 +0000 (UTC), "Reg Edwards"
wrote:


I was running 100 watts from a Kenwood TS-520. The bedroom light was
not being run from the 240-volt power wiring to the TS-520. After
years of thinking about it, I have never found an entirely
satisfactory explanation.

To add complexit to this puzzle, was your dinner being cold caused to
some extent by the apparent drop in mains voltage at the light socket
in the shack (bedroom)?

Did your light have a phase controlled dimmer (you know, to set the
mood)... they not only emitted huge quantities of RF, they were also
very susceptible to ingress of RF.

It wasn't by chance some other interaction like RF interference with
street lighting controllers and the street likes were operating in
sympathy with your keying?

Perhaps some other on-site high power appliance affected by RF. I had
one of the early heaters with a fully solid state thermostat that was
susceptible to RFI, and it took a while to work out why when I went
into my office sometimes the heater had been running even though it
appeared to be "off"... until I associated the effect with recent
on-air activity.

At my coastal retreat, SSB RF was getting into the irrigation
controller recently, causing water hammer in sympathy with speech.

There are limitless possibilities!

Owen
--

Reg;

As I said it was my guess. That's what you get for guessing. It would
seem that your house has sufficient capacity to carry a 60 watt light
bulb and a 100 watt transmitter.

If you ever find out what happened let the group know.

Maybe I'll meet you on the air some day.

Dave WD9BDZ


Reg Edwards wrote:

As to you lamp dimming, I do not know what the wiring capacity of

your

house was but the transmitter was being fed by the same mains drop

from

the street as the lamp. That is, IMO, the most likely cause of the
dimming. Just my guess.

Dave WD9BDZ


=======================================
Dave,

The mains supply from the road was capable of 50 kilowatts without
excessive volts drop. For a few years it was used for electric
cookers, several 3-bar central heating radiators, etc., without
problems. Far more than the TS-520 with an RF power output of 100
watts.

There may been something very peculiar with the 60-watt bedroom
filament lamp which caused it to cool off when both RF plus 50Hz power
currents flowed through it. I didn't try another bulb.

There may have been incorrect house wiring such that the only power
point in the bedroom, used for the transmitter, was connected, by
mistake, to the lighting circuit. But even then, the lighting circuit
should have been capable of withstanding the load of the transmitter
without much of a voltage drop. Shortly afterwards I moved the shack
downstairs into the garage. At the time I never checked house wiring
and later on the family sold the house and moved. The new owner was
not a radio amateur.
----
Reg, G4FGQ.

Dave Platt wrote:

It doesn't take all that much of a drop in voltage to result in a
visible change in the brightness of an incandescent-filament light.
According to one site I've found, light output is roughly proportional
to the voltage raised to a power between 3.1 and 3.4. A 5% drop in
voltage would thus result in a decrease in light level of more than
15%, which would be pretty easy to notice.

If you were transmitting 100 watts CW key-down, I'd guess that your
transmitter was probably drawing at least 300 watts from the
mains, and perhaps rather more depending on its design.

Add a few more likely or possible elements e.g. a linear power supply
which tends to draw most of its current from the mains during the
voltage peaks (and thus causes a disproportionate amount of voltage
sag on the lines during those peaks), insufficiently-thick house
wiring in the walls, and perhaps a slightly loose or corroded
connection to one of the outlets or switches or breakers, and I can
well believe that keying a 100-watt CW transmitter could cause enough
voltage drop to result in visible dimming of the lamp bulb.

A friend of mine back in the 70's had me come over to listen to his new
stereo. It was a Phase Linear system as I recall. The speaker cabinets
had 9 components each in them. We put "Hall of the Mountain King" on
the turntable and turned up the level to the point just before it began
to distort. The power amp was pretty substantial and I noticed the
lights were dimming to the music. I went outside and could see the
power meter change speed in time to the music. And this was in an
industrial building. That was the loudest home stereo system I ever
heard. Probably the best sounding as well.

ac6xg