I have come to the conclusion the only antenna I am going to be able to use
is a ground mounted dipole or random wire. No antenna supports in the yard,
no fences, no attic. I tried a vertical "flagpole" but it is just too noisy.
Nothing but me and the yards of my two neighbours. I am able to run about
60 feet of 22 gauge green enameled wire along the length of the yards. I
have done extensive reading on NVIS propagation, but I'm curious if anyone
is actually using this method on 160, 80 or 40m.

Thanks,

Max

In rec.radio.amateur.antenna, you wrote:
have done extensive reading on NVIS propagation, but I'm curious if anyone
is actually using this method on 160, 80 or 40m.

I am using a 100 foot long wire about 6ft off the ground (basically a wire
tacked to a wooden fence). I am able to make contacts out to about 400
miles on 40m, but have not tried it on 160 or 80. Funny thing is that it
works really well on 6m (when the band is open) with contacts in the
1000+ mile range.


Alex / AB2RC

Max, VE3TMT wrote:
"I have come to the conclusion that the only antenna I am going to be
able to use is a ground mounted dipole or random wire."

Don`t expect much NVIS broadside to a dipole on the ground unless it`s
on deep dry sand.

For NVIS the ideal height over the effective earth reflector is about
1/4-wave. This is because the earth is 90-degrees away from the
radiator. This makes a round-trip for the signal of 180-degrees. This
added to the 180-degrees of phase inversion produced in reflection gives
a total of 360-degrees so that the reflected wave when it returns to the
radiator is back in-phase with the new emissions which are headed in the
same direction, that is toward the zenith (straight up).

Lowering the height of the radiator shifts the phase between the two
signal components from directly in-phase at 1/4-wave distance between
radiator and reflector sites to out-of-phase at zero distance between
their sites.

At zero height the radiator and earth behave as a lossy single-wire
transmission system where opposing polarities nullify radiation
broadside to the radiator.

Hope for effective radio communications using a near to the earth
antenna comes in the form of a Beverage antenna. I`ve used a Beverage
antenna very successfully for sky-wave tnans-Atlantic reception in
Portugal of WCBS in New York, and WWL in New Orleans.

The 1945 War Department book, "Electrical Communication Systems
Engineering" on page 317 says:
"Insulated wires of sufficient length laid on the ground, or better yet
on vegetation just above the ground, will provide ground-wave
transmission with vertical polarization in line with the direction of
the wire, that is, off either end of the wire, and for moderate
horizontal angles from this direction. Such low antennas have the
advantage of being easily concealed. A length of about 600/F feet (where
F is the frequency in megacycles), or somewhat longer, is suitable, if
the length is adjusted by trial to permit good transmitter loading. A
100-foot on-ground antenna attached to Radio Set SCR-536 (handie-talkie)
gives at least as good transmission in such directions as the whip
supplied with the set, and can be more easily concealed. Half-wave
on-ground antennas---can sometimes be used for short distance sky-wave
reception or transmission."

Stealth has a price to pay in efficiency when low height must be used.

Best regards, Richard Harrison, KB5WZI

hmmm, this stuff I have read on NVIS says 0.1 to 0.2 wavelengths. I can find
the source if anyone is interested (I am not at home right now). I am
certainly not arguing (I have no problem arguing, but this is one of many
subjects about which I have very little knowledge), Richard, just mentioning
a difference in what I have read.

Paul AB0SI


"Richard Harrison" wrote in message
...
Max, VE3TMT wrote:
"I have come to the conclusion that the only antenna I am going to be
able to use is a ground mounted dipole or random wire."

Don`t expect much NVIS broadside to a dipole on the ground unless it`s
on deep dry sand.

For NVIS the ideal height over the effective earth reflector is about
1/4-wave. This is because the earth is 90-degrees away from the
radiator. This makes a round-trip for the signal of 180-degrees. This
added to the 180-degrees of phase inversion produced in reflection gives
a total of 360-degrees so that the reflected wave when it returns to the
radiator is back in-phase with the new emissions which are headed in the
same direction, that is toward the zenith (straight up).

Lowering the height of the radiator shifts the phase between the two
signal components from directly in-phase at 1/4-wave distance between
radiator and reflector sites to out-of-phase at zero distance between
their sites.

At zero height the radiator and earth behave as a lossy single-wire
transmission system where opposing polarities nullify radiation
broadside to the radiator.

Hope for effective radio communications using a near to the earth
antenna comes in the form of a Beverage antenna. I`ve used a Beverage
antenna very successfully for sky-wave tnans-Atlantic reception in
Portugal of WCBS in New York, and WWL in New Orleans.

The 1945 War Department book, "Electrical Communication Systems
Engineering" on page 317 says:
"Insulated wires of sufficient length laid on the ground, or better yet
on vegetation just above the ground, will provide ground-wave
transmission with vertical polarization in line with the direction of
the wire, that is, off either end of the wire, and for moderate
horizontal angles from this direction. Such low antennas have the
advantage of being easily concealed. A length of about 600/F feet (where
F is the frequency in megacycles), or somewhat longer, is suitable, if
the length is adjusted by trial to permit good transmitter loading. A
100-foot on-ground antenna attached to Radio Set SCR-536 (handie-talkie)
gives at least as good transmission in such directions as the whip
supplied with the set, and can be more easily concealed. Half-wave
on-ground antennas---can sometimes be used for short distance sky-wave
reception or transmission."

Stealth has a price to pay in efficiency when low height must be used.

Best regards, Richard Harrison, KB5WZI

On Fri, 05 Dec 2003 16:44:04 GMT, "
wrote:

hmmm, this stuff I have read on NVIS says 0.1 to 0.2 wavelengths. I can find
the source if anyone is interested (I am not at home right now). I am
certainly not arguing (I have no problem arguing, but this is one of many
subjects about which I have very little knowledge), Richard, just mentioning
a difference in what I have read.

Paul AB0SI

Hi Paul,

The troops, during Desert Storm, achieved NVIS by laying the antenna
on the ground. I will add, that like Richard points out, it was sand.

Logic would suggest that an antenna very close to ground has no chance
of launching much energy tangential to the earth's surface (a direct
short), leaving what's left to go straight up and hazard a bounce from
above. If you raise that antenna to a quarter wave up, you simply
optimize the straight up radiation, but you also lose a lot of the
immediate ground loss that snubbed the tangential angles.

What few dipole users would admit (because they love to crow about not
having radials) is that if you add radials, you can further improve
your dipole performance up AND tangentially.

73's
Richard Clark, KB7QHC

On Fri, 05 Dec 2003 18:52:30 GMT, Richard Clark
wrote:



What few dipole users would admit (because they love to crow about not
having radials) is that if you add radials, you can further improve
your dipole performance up AND tangentially.

Where would I attach radials on a dipole?

Bob
k5qwg

73's
Richard Clark, KB7QHC

On Fri, 05 Dec 2003 13:03:34 -0600, Bob Miller
wrote:

On Fri, 05 Dec 2003 18:52:30 GMT, Richard Clark
wrote:
What few dipole users would admit (because they love to crow about not
having radials) is that if you add radials, you can further improve
your dipole performance up AND tangentially.

Where would I attach radials on a dipole?


Hi Bob,

Not to the dipole certainly; to the ground below the dipole. It is,
after all, the ground that presents the loss. The radials reduce that
loss as is their function.

For example, a 20M dipole one halfwave over a ground mat (1M grid
about 1 wavelength in XY dimension), shows a gain of 7dBi at 30°.

Take away that ground mat, it shows a gain of 6.5dBi at that same 30°.

Nothing remarkable in my book, but I have the ground mat anyway.

73's
Richard Clark, KB7QHC

Bob Miller wrote:
On Fri, 05 Dec 2003 18:52:30 GMT, Richard Clark
wrote:



What few dipole users would admit (because they love to crow about not
having radials) is that if you add radials, you can further improve
your dipole performance up AND tangentially.


Where would I attach radials on a dipole?

Just remove the bias plys and substitute the radials! 8^)

But seriously, they are set the same way as you would on a vertical, in
the ground. And Richard is right.

- Mike KB3EIA -

Paul, AB0SI wrote:
"hmmm, this stuff I have read on NVIS says 0.1 to 0.2 wavelengths."

Yes, and I said 0,25 and explained how I arrived at that figure. So, I
went to page 3-11 of the 19th edition of the ARRL Antenna Book to look
at Fig 12.

Fig 12(A) is for 1/8-WL high and Fig 12(B) is for 1/4-WL high. Paul is
supported by Fig 12 because the 1/8-WL high antenna appears to have more
radiation toward the zenith than does the 1/4-WL high antenna.

I don`t know why, but would speculate it is due to closer coupling of
the radiator with the earth which gives the reflector (earth) more
energy to work with on the reflection. Maybe I`ll learn something from
this bum steer. I learn something nearly every day here and find this a
rewarding experience.

Best regards, Richard Harrison, KB5WZI

Richard:

Interesting, thanks. This is one of the few places it seems where folks can
have a reasonable conversation without it quickly turning into a
name-calling contest. You idea of why a lower elevation works a bit better
sounds reasonable. I just remember the empirical fact. Sort of like a 5-year
old's reason for do anything --- b'cause!

Paul AB0SI


"Richard Harrison" wrote in message
...
Paul, AB0SI wrote:
"hmmm, this stuff I have read on NVIS says 0.1 to 0.2 wavelengths."

Yes, and I said 0,25 and explained how I arrived at that figure. So, I
went to page 3-11 of the 19th edition of the ARRL Antenna Book to look
at Fig 12.

Fig 12(A) is for 1/8-WL high and Fig 12(B) is for 1/4-WL high. Paul is
supported by Fig 12 because the 1/8-WL high antenna appears to have more
radiation toward the zenith than does the 1/4-WL high antenna.

I don`t know why, but would speculate it is due to closer coupling of
the radiator with the earth which gives the reflector (earth) more
energy to work with on the reflection. Maybe I`ll learn something from
this bum steer. I learn something nearly every day here and find this a
rewarding experience.

Best regards, Richard Harrison, KB5WZI