From: gary@ke4zv.uucp (Gary Coffman)
Newsgroups: rec.radio.cb
Subject: Re: AM or SSB
Date: 15 Apr 92 18:08:53 GMT
Reply-To: gary@ke4zv.UUCP (Gary Coffman)
Organization: Gannett Technologies Group

In article <1992Apr13.141706.3785@iscsvax.uni.edu> fisher2557@iscsvax.uni.edu writes:
>In article <11337@ksr.com>, jfw@ksr.com (John F. Woods) writes:
>>>with skip, ANYTHING'S possible.  Point-to-point (ground waves; the reliable
>>>ones) normal for me is 30 miles.  That's my base (ground plane just abouve my
>>>house) to a mobile with a k-40.  If I had a beam, and was talking with another
>>>base with another beam, I could expect in excess of 100 miles.  When you get
>>>going THAT far, though, you're not really throwing the signal thru the air;
>>>your signal is almost totally on your ground-plane, so if you don't have a
>>>WELL grounded antennae, you're S.O.L....
>> 
>> "Ground wave" and "ground plane" have nothing to do with each other.
>> Quoting from the 1984 Radio Amateur's Handbook:
>>   The "ground wave" is that portion of the radiation which is directly affected
>>   by the surface of the earth.  It has two components, an earth-guided surface
>>   wave, and the space wave.  The latter is the resultant of two components,
>>   direct and ground reflected.
>> 
>(some lines removed)
>> 
>> Your local ground plane will not affect ground wave propagation much, unless
>> it happens to be a couple of hundred miles across.  Its design may lower the
>> angle of radiation and help some; a poor ground plane will make a vertical
>> antenna work poorly, both for ground wave and other forms of propagation.
>> 
>> The ARRL Antenna Book contains a lot of information about propagation and
>> antennas (naturally).
>> 
>> John Woods, WB7EEL
>
>I guess I did not use the right words in my posting....  What I was trying to
>say is that the antennae has *two* parts, the stinger and the ground plane. 
>Normally, you use the stinger as your main element of transmission.  The
>stinger accounts for about 91% of your radiated power.  The other 9% is put out
>on the ground radials.  (recall that the rf bleeds off the high voltage nodes
>of the stinger (at the tip of a 5/8) and there has to be a SOURCE of those
>electrons...  they're "pulled" from the ground plane, and generate a signal) 
>The action of the ground plane would be 50/50 with the stinger if the ground
>weren't such a good source of electrons, flooding out the signal.  When you
>talk much beyond 20% past line-of-sight (the antennae's sight, not yours on the
>ground) you CANNOT put a stinger signal through without bouncing it off
>something like an atmospheric layer.  Any two people 100+ miles away that do
>not have *high* antennaes or a valley between them are talking purely on .....
>I lack the proper term....  I wanna say "ground waves" but as you pointed out,
>that's not right...  UNDERground waves.  that's the word.  Beam antennaes also
>direct this signal. (I don't believe polarization matters underground,either)
>By the way, I've got the 1990 ARRL at home, too.  BIG book!  I wish they had
>some info on VOXes.....  I'd REALLY like to make one. :(  Thanks for the
>correction, though.  Gotta have somebody keep me on my toes.

Oh dear. Nathan there are so many misconceptions and wrong statements in
this that I don't know where to begin. I'll try to keep this simple and
not bring Maxwell's equations into it.

First off, a vertical monopole needs a ground plane to act as a *current
mirror* to supply the missing half of an electrical dipole. If it is
built and tuned properly, half the current and half the radiation comes
from the vertical member and half from the ground plane. RF radiation
occurs because of *current* flow. This current induces a magnetic field
in the surrounding medium. When the current reverses, an electric
field is induced by the collapsing magnetic field. When the current
reverses again, the electric field collapses and induces another magnetic
field. These expand outward from the current source at the speed of
light. The energy swaps back and forth between an electric field and
a magnetic field at a rate that describes the *frequency* of the radiation.

Electrons neither enter nor leave the antenna. Instead they oscillate
back and forth along the *resonant* length of the antenna structure.
It's this movement of electrons, a *current*, that induces the fields
that make up RF radiation. Radiation is strongest from the current maxima
and weakest from the current minima. In a half wave antenna, current is
maximum at the center and zero at the ends. In a quarterwave antenna over
a ground plane, the current is maximum at the feed point and minimum at
the tip. With the 5/8 wave antenna, maximum current is displaced up the
monopole about 30% between the feed point and the tip. Voltage is maximum
at the tip and minimum at the current maxima. Voltage is the *potential*
for doing work and doesn't directly generate *any* radiation. When that
potential drives a *current*, work is done and radiation generated. A
resonant antenna has *standing waves* of voltage and current on it that
are displaced 90 degrees from each other in phase. This is the necessary
and sufficient condition to allow maximum radiation from the antenna.

Radio line of sight range is about 20% greater than optical line of 
sight. This is direct transmission from one antenna to another.
Ground wave on the other hand has a *guided* wave component that
stays in the air-ground interface as the Earth curves. Ground wave
is usable much beyond radio line of sight range, out to 100 or more
miles depending on power and soil conductivity. Ground wave exists
due the the extreme dielectric constant difference between earth and
air. It is an extreme form of the refraction that allows ionospheric
"skip" transmissions. Due to the usually poor conductivity of the
earth, the signal strength drops rapidly with distance, unlike skywave
propagation where the ionized atmosphere furnishes a nearly lossless
medium for the wave.

This is why broadcast stations run a lot of power, to overcome ground
losses in the ground wave. In CB terms, a "kicker" does little good
for shooting skip or for working line of sight, but can be an enormous
aid to working extended ground wave communications beyond the line of
sight but less than the first skip zone.

*Read* that Handbook Nathan. Much of this is covered in the theory
chapters.

Gary KE4ZV