JP,

If IIRC the one Radial that helps the most, is the one
that lays directly under the Horizontal Out-Arm of the
Inverted "L" Antenna.

This is why I suggest that 'if' possible to Flip Starting
Point (Back-to-Front) with the Vertical Up-Leg of the
Inverted "L" Antenna and have the Coax Cable Feed-in-Line
lay directly under the Horizontal Arm of the Inverted "L"
Antenna.

READ - Flipping the Inverted "L" Antenna 'Back-to-Front'
= Better Performance
http://groups.yahoo.com/group/Shortw...a/message/2013
http://groups-beta.google.com/group/...79890656d94af1

Maybe some one could use some software amd 'model' a
Shortwave Listener's (SWLs) Inverted "L" Antenna with
a single Ground Radial directly under the Horizontal
Out-Arm.

# 1 The 'small' SWL (V1:H2) Inverted "L" Antenna using a
15 Foot Vertical Up-Leg and 30 Foot Horizontal Out-Arm
Plus 30 Foot Ground Radial directly under the Horizontal
Out-Arm section of the Antenna.
..
# 2 The 'medium' SWL (V1:H2.5) Inverted "L" Antenna using a
20 Foot Vertical Up-Leg and 50 Foot Horizontal Out-Arm
Plus 50 Foot Ground Radial directly under the Horizontal
Out-Arm section of the Antenna.

# 3 The 'large' SWL (V1:H3) Inverted "L" Antenna using a
25 Foot Vertical Up-Leg and 75 Foot Horizontal Out-Arm
Plus 75 Foot Ground Radial directly under the Horizontal
Out-Arm section of the Antenna.

Test Results should be provided for these Shortwave Bands :
@ 60M Band ~ 5 MHz
@ 49M Band ~ 6 MHz
@ 31M Band ~ 9.7 MHz
@ 25M Band ~ 11.8 MHz
@ 22M Band ~ 13.7 MHz
@ 19M Band ~ 15.5 MHz

iane ~ RHF

Jack Painter wrote:

"starman" wrote
Jack Painter wrote:
The best place to terminate the antenna and mount the Balun is *at* the
ground rod, which means the connection is about 4 inches long. Ty-wrap
the
Balun to the protruding ground rod. After applying coax-seal to the
wire-wrapped and then soldered connections, cut the bottom and slit one
side
of a plastic beverage bottle to just fit over the Balun and tape the
bottle
shut afterwards. Spray paint the bottle with bow-flex cammo and it
becomes
part of the background, and weather-proofed for years of service. Some
designs advise terminating the vertical drop of the inverted-L about 6
feet
above ground. That's more important for a center fed or off-center fed
(dipole type) antenna than the end-fed wires. Users should have no
problems
terminating the inverted-L at ground level, and sink a good ground rod
(with
buried radials if you desire) at that same point.

I mounted my balun in a plastic electrical junction box with a cover
gasket, the kind used with plastic conduit. The ground wire to the rod
is about 2-feet long.

Something I intend to experiment with, is running two radials from the
Balun/ground/feedpoint; one under the entire length of the antenna and the
other 180 degrees away from the feedpoint. Since this antenna was
deliberately located as far from the house as possible (on the property
line), I could not run radials in a 360 degree fashion. But I think if
radials will help at all, two of them (at 0 and 180 degrees) would show
results. Ever try this? The antenna is for 2182 thru 16000 khz marine.

Jack

I've never tried ground radials but it's worth a try. Would you still
run a short ground wire too?

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"starman" wrote
Jack Painter wrote:

"starman" wrote
Jack Painter wrote:
The best place to terminate the antenna and mount the Balun is *at*
the
ground rod, which means the connection is about 4 inches long.
Ty-wrap
the
Balun to the protruding ground rod. After applying coax-seal to the
wire-wrapped and then soldered connections, cut the bottom and slit
one
side
of a plastic beverage bottle to just fit over the Balun and tape the
bottle
shut afterwards. Spray paint the bottle with bow-flex cammo and it
becomes
part of the background, and weather-proofed for years of service.
Some
designs advise terminating the vertical drop of the inverted-L about
6
feet
above ground. That's more important for a center fed or off-center
fed
(dipole type) antenna than the end-fed wires. Users should have no
problems
terminating the inverted-L at ground level, and sink a good ground
rod
(with
buried radials if you desire) at that same point.

I mounted my balun in a plastic electrical junction box with a cover
gasket, the kind used with plastic conduit. The ground wire to the rod
is about 2-feet long.

Something I intend to experiment with, is running two radials from the
Balun/ground/feedpoint; one under the entire length of the antenna and
the
other 180 degrees away from the feedpoint. Since this antenna was
deliberately located as far from the house as possible (on the property
line), I could not run radials in a 360 degree fashion. But I think if
radials will help at all, two of them (at 0 and 180 degrees) would show
results. Ever try this? The antenna is for 2182 thru 16000 khz marine.

Jack

I've never tried ground radials but it's worth a try. Would you still
run a short ground wire too?

Per above, my 4:1 Balun/coax-feedpoint is already attached/connected
directly to a ground rod, not just near one. The radials will both be part
of common ground already, their tie-point at the same ground rod that the
feedpoint and Balun are attached to. Radials are normally shallow-buried,
both for protection and to minimize pickup of yet more noise. It's a lot of
work to bury long radials, so I will first just lay them out along the
surface, then experiment with various coastal stations to determine if there
is any gain from the radials.

Due to the lightning protection design at my station, any new ground radials
also have to be bonded to the station ground and AC service entry ground,
the entire system is common-bonded. Because it's winter time and small
likelihood of lightning (we had a nearby strike during a snowstorm 2 weeks
ago!) I will wait to add the bonding conductors until after the antenna is
tested for any possible xmit/receive improvements. Those bonding connectors
will have to run 90 degrees from the end of each of the two new radials,
and they may also alter the radiation pattern of the antenna. I'll let you
know how that works out.

Jack

In article , starman
wrote:

Jack Painter wrote:

"starman" wrote
Jack Painter wrote:
The best place to terminate the antenna and mount the Balun is
*at* the ground rod, which means the connection is about 4
inches long. Ty-wrap the Balun to the protruding ground rod.
After applying coax-seal to the wire-wrapped and then soldered
connections, cut the bottom and slit one side of a plastic
beverage bottle to just fit over the Balun and tape the bottle
shut afterwards. Spray paint the bottle with bow-flex cammo and
it becomes part of the background, and weather-proofed for
years of service. Some designs advise terminating the vertical
drop of the inverted-L about 6 feet above ground. That's more
important for a center fed or off-center fed (dipole type)
antenna than the end-fed wires. Users should have no problems
terminating the inverted-L at ground level, and sink a good
ground rod (with buried radials if you desire) at that same
point.

I mounted my balun in a plastic electrical junction box with a
cover gasket, the kind used with plastic conduit. The ground wire
to the rod is about 2-feet long.

Something I intend to experiment with, is running two radials from
the Balun/ground/feedpoint; one under the entire length of the
antenna and the other 180 degrees away from the feedpoint. Since
this antenna was deliberately located as far from the house as
possible (on the property line), I could not run radials in a 360
degree fashion. But I think if radials will help at all, two of
them (at 0 and 180 degrees) would show results. Ever try this? The
antenna is for 2182 thru 16000 khz marine.

Jack

I've never tried ground radials but it's worth a try. Would you still
run a short ground wire too?

If a ground wire is not short it will not behave as if it is connected
to ground period.

The problem is that a wire has inductance. The value of inductance is
based on the diameter of the wire or cross sectional area for other
shapes over its length. The smaller the cross sectional area is or the
longer the wire the is the higher the inductance of that wire.

The inductance of the wire will become a greater problem at higher
frequencies and less of a problem the lower in frequency you want to
operate on because the reactance of the wire always increases with
frequency.

Since you want the wire to behave as a ground connection you have to
calculate its self inductance and then its inductive reactance at the
highest frequency you want it to behave as a ground connection.

If you don't want to calculate it then make it as short as practical.
If the connection turns out to be more than a few inches in length then
use three inch minimum width copper tape instead of wire.

--
Telamon
Ventura, California

Telamon wrote:

In article , starman
wrote:

I've never tried ground radials but it's worth a try. Would you still
run a short ground wire too?

If a ground wire is not short it will not behave as if it is connected
to ground period.

The problem is that a wire has inductance. The value of inductance is
based on the diameter of the wire or cross sectional area for other
shapes over its length. The smaller the cross sectional area is or the
longer the wire the is the higher the inductance of that wire.

The inductance of the wire will become a greater problem at higher
frequencies and less of a problem the lower in frequency you want to
operate on because the reactance of the wire always increases with
frequency.

Since you want the wire to behave as a ground connection you have to
calculate its self inductance and then its inductive reactance at the
highest frequency you want it to behave as a ground connection.

If you don't want to calculate it then make it as short as practical.
If the connection turns out to be more than a few inches in length then
use three inch minimum width copper tape instead of wire.

Given all the talk about grounding systems on this group in the past, I
think most of us here know that a good RF ground wire must be short to
avoid introducing too much inductance into the grounding system. I asked
the question because I wanted to know more about the relationship
between a good (short) RF ground wire and a ground radial system. Does
one work better than the other or should both be used together? Where's
John Doty when we need him? :-)

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jimg wrote:
it's always important to keep the ground wire length well below 1/4
wavelength of the max freq your interested in. Assuming it's short
enough to prevent distributed effects, the self inductance of a
straight 16ga wire is about 0.33uH/foot...so 50' at 10MHz is about
1Kohm...thats a fair amount of impedance and is why you pick up all
that noise.....

so what's the ground radial system do? in short, it provides the
counter-poise to the wire strung in the sky. the antenna-ground system
create the differential signal which is applied to your receiver's rf
amp...the better the ground poise, the more 'sensitive' your
antenna...is this some kind of linear relationship? like double the
ground system and double the antenna sensitivity...nope , not that
simple and there's not enuf room here to make all the variables
clear...but the better the grounding system, the better your antenna
will "work"...some ppl have a good enough conduction under the soil
that a simple 10' ground rod intersects this "layer" and the dx cpmes
rolling in...other ppl have rods sunk in the earth and buried in wild
patterns all over the yard to get the same effect.....

so the simple answer(s) is: your ground wire length influences noise
(what we call common-field) pick-up so shorter is better; the ground
radial system improves the signal strength at the receiver
input...and i hate simple answers to a very complicated system...


Telamon wrote:

In article , starman
wrote:

I've never tried ground radials but it's worth a try. Would you still
run a short ground wire too?

If a ground wire is not short it will not behave as if it is connected
to ground period.

The problem is that a wire has inductance. The value of inductance is
based on the diameter of the wire or cross sectional area for other
shapes over its length. The smaller the cross sectional area is or the
longer the wire the is the higher the inductance of that wire.

The inductance of the wire will become a greater problem at higher
frequencies and less of a problem the lower in frequency you want to
operate on because the reactance of the wire always increases with
frequency.

Since you want the wire to behave as a ground connection you have to
calculate its self inductance and then its inductive reactance at the
highest frequency you want it to behave as a ground connection.

If you don't want to calculate it then make it as short as practical.
If the connection turns out to be more than a few inches in length then
use three inch minimum width copper tape instead of wire.

Given all the talk about grounding systems on this group in the past, I
think most of us here know that a good RF ground wire must be short to
avoid introducing too much inductance into the grounding system. I asked
the question because I wanted to know more about the relationship
between a good (short) RF ground wire and a ground radial system. Does
one work better than the other or should both be used together? Where's
John Doty when we need him? :-)

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jimg
Oregon
USA

"jimg" wrote
it's always important to keep the ground wire length well below 1/4
wavelength of the max freq your interested in. Assuming it's short
enough to prevent distributed effects, the self inductance of a
straight 16ga wire is about 0.33uH/foot...so 50' at 10MHz is about
1Kohm...thats a fair amount of impedance and is why you pick up all
that noise.....

so what's the ground radial system do? in short, it provides the
counter-poise to the wire strung in the sky. the antenna-ground system
create the differential signal which is applied to your receiver's rf
amp...the better the ground poise, the more 'sensitive' your
antenna...is this some kind of linear relationship? like double the
ground system and double the antenna sensitivity...nope , not that
simple and there's not enuf room here to make all the variables
clear...but the better the grounding system, the better your antenna
will "work"...some ppl have a good enough conduction under the soil
that a simple 10' ground rod intersects this "layer" and the dx cpmes
rolling in...other ppl have rods sunk in the earth and buried in wild
patterns all over the yard to get the same effect.....

so the simple answer(s) is: your ground wire length influences noise
(what we call common-field) pick-up so shorter is better; the ground
radial system improves the signal strength at the receiver
input...and i hate simple answers to a very complicated system...


Well put. It's good to keep it simple! Some re-emphasis:

RF GROUND is at the transmitter-side, where avoidance of 1/4 wave length
prevents monster impedance that is not felt as ground at all. A short path
to multiple ground rods connected in parallel completely avoids this 1/4
wave effect no matter what frequency you xmit on. XMTR RF GROUND has no
effect on receiving at all, *if * the static grounding and radials (below)
are used.

STATIC/LIGHTNING GROUND is grounding the coax-shield at several points,
beginning right outside the shack, at the base of a wire antenna or tower,
mid-point, and top of tower.

RADIALS are for reflecting transmitted energy from the antenna that would
otherwise be lost (absorbed) by the earth. They have a much smaller but
measurable benefit to the receiving aspect of any antenna. They can be above
ground (right under an elevated vertical, where very short lengths work),
along the surface of the ground on a ground-based vertical, or buried in a
large pattern around a vertical, center-fed inverted-L, or in some cases,
random wires or inverted-L's. A 1/2 wave horizontal dipole is a "complete"
antenna and has no benefit from radials, but it must be elevated
sufficiently to avoid ground losses. The coax-shield of feedline to a dipole
should still be grounded per above para.

--

WARNING: That ground screw on the back of your receiver set could get you in
more trouble than it's worth. First, the receiver-case is already grounded
via your home's electrical system. Noise and static on the coax-shield
should be shorted to ground outside from coax-shield grounding. If you
connect your receiver to a separate outside ground, you have major lightning
issues if you leave that receiver-ground connected during storms. This is
true even if *everything* else is disconnected. If any tree or structure
within up to several hundred feet of your property is struck by lightning,
your ground system will be a sink for some of that energy, and draw it right
into the radio via ground connections. Of course the antennas would add to
this problem, but most people remember to disconnect them before a storm.
Putting disconnected antenna feedlines in a mason-jar is an embarrassing
practice that I got away with for about ten years, and I'm sure many
hobbyists play the same odds. Better than nothing (which is the glass-jar
trick) would be to short the antennas to an RF-ground, if you have one.

If you decide that a separate receiver-ground is important, you should
consider what you will do with that "hot-wire" before lightning occurs
anywhere in a wide-area around your property.

Jack Painter
Virginia Beach, Virginia

jimg wrote:

jimg wrote:
it's always important to keep the ground wire length well below 1/4
wavelength of the max freq your interested in. Assuming it's short
enough to prevent distributed effects, the self inductance of a
straight 16ga wire is about 0.33uH/foot...so 50' at 10MHz is about
1Kohm...thats a fair amount of impedance and is why you pick up all
that noise.....

so what's the ground radial system do? in short, it provides the
counter-poise to the wire strung in the sky. the antenna-ground system
create the differential signal which is applied to your receiver's rf
amp...the better the ground poise, the more 'sensitive' your
antenna...is this some kind of linear relationship? like double the
ground system and double the antenna sensitivity...nope , not that
simple and there's not enuf room here to make all the variables
clear...but the better the grounding system, the better your antenna
will "work"...some ppl have a good enough conduction under the soil
that a simple 10' ground rod intersects this "layer" and the dx cpmes
rolling in...other ppl have rods sunk in the earth and buried in wild
patterns all over the yard to get the same effect.....

so the simple answer(s) is: your ground wire length influences noise
(what we call common-field) pick-up so shorter is better; the ground
radial system improves the signal strength at the receiver
input...and i hate simple answers to a very complicated system...

That's a good start. The radials make the signal stronger and a good RF
ground makes it quieter. Both add to the intelligibility of the signal.

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JP,
..
Mason-Jar ? Great Balls of Lightning ! ;-}
..
I have used old metal Film Canisters each mounted
to the stations Ground Buss; one per PL-259 Plug.
..
Also a small tall Tin Can mounted to the stations Ground
Buss with two to Four PL-259 Plugs jammed it to it.
..
Now I use an Alpha-Delta Antenna Switch with a
"Disconnected-and-Grounded" Center Position
when things are not in use.
http://www.universal-radio.com/catalog/switch/2415.html
http://www.universal-radio.com/catalog/switch/1864.html
http://www.universal-radio.com/catalog/switch/2811.html
..
iane ~ RHF

"RHF" wrote
JP,
.
Mason-Jar ? Great Balls of Lightning ! ;-}
.
I have used old metal Film Canisters each mounted
to the stations Ground Buss; one per PL-259 Plug.
.
Also a small tall Tin Can mounted to the stations Ground
Buss with two to Four PL-259 Plugs jammed it to it.
.
Now I use an Alpha-Delta Antenna Switch with a
"Disconnected-and-Grounded" Center Position
when things are not in use.
http://www.universal-radio.com/catalog/switch/2415.html
http://www.universal-radio.com/catalog/switch/1864.html
http://www.universal-radio.com/catalog/switch/2811.html
.
iane ~ RHF

I thought you would get a kick out of the mason-jar trick! Live and learn.

What are your Alpha-Delta Antenna Switches "grounded" to when in the center
position? Where are they mounted?

Some of you will remember I operate a USCG Auxiliary communications station,
and when on duty, do not secure for wx. That required a complete lightning
protection system which cost about $4500 in electrical design, labor and
materials (surge suppression), plus another several hundred in materials
(external ground system and bonding) which I installed. That does not
include the standby power (generator) btw. I researched the grounding,
bonding and surge suppression issues for over two years before embarking on
that plan. Also studied the damages that occurred to stations (amateur,
broadcast and government) who had lightning protection systems, and those
that did not. I still follow every published story of lightning damage to US
communication stations, and have a current library of (US) NEC and NFPA
codes.

My system's baptism by fire came the same afternoon the contractors were
cleaning up to leave in July 2004. Over 1,000 strikes in a 10 mile area,
about 300 in my immediate area, and perhaps a dozen almost on top of me.
Trees in my yard and on both sides of my HF antennas were struck, and the
power spiked relentlessly, eventually calling for the generator due to
electrical noise and high voltages. Dozens of electrical storms later, the
system continues to perform as expected.

When I give advice to SWL hobbyists about lightning safety, it's because I
went through years of worry and learning curves of what works, what doesn't,
and the safest ways to operate (or isolate) from various stages of hobby
listening, to nearly full-time service for the USCG.

Although the antenna systems have changed somewhat from the schematics on
the website, the basic system is described at
http://members.cox.net/pc-usa/station/ground0.htm

This is the time btw, to commence any plans some of you may have had to
install or upgrade lightning protection systems, not in the Spring or Summer
when thunderstorms can occur without warning! O.K. Steve in Detroit you will
have to wait until the ground thaws, lol.

Jack Painter
Virginia Beach, Virginia