by Rob » Mon, 25 Oct 1999 04:00:00
Has anyone had on air experience with both types of antennas??
73's
Rob
by dm » Mon, 25 Oct 1999 04:00:00
by William F. Hage » Mon, 25 Oct 1999 04:00:00
> Which antenna is a better DX antenna at low elevations - the wave wave
> vertical or the half wave vertical dipole??
> (I understand that the half wave vertical dipole is the easiest to feed with
> 50 ohm coax but I don't mind building a matching system for a half wave
> vertical if it is worth it for DX)
> Has anyone had on air experience with both types of antennas??
> 73's
> Rob
by dm » Mon, 25 Oct 1999 04:00:00
by Brian Kel » Mon, 25 Oct 1999 04:00:00
I have. I've put up several of both. I'll take the dipole if I have aQuote:>Has anyone had on air experience with both types of antennas??
Brian Kelly w3rvQuote:>73's
>Rob
by Fracten » Tue, 26 Oct 1999 04:00:00
It IS?Quote:>I'm with KC6UFE...and would add that a full half wave "radiator" is
>something like 1.5 db stronger in field intensity than a quarter wave
>"radiator".
That is incorrect. According to this logic, an 1/8 wave, lossless dipole is 3Quote:> This is due to a full current "loop" on it versus only a half
>a current loop on the shorter one.
According to this logic, an infinitesimal losslessloop has zero dBi, when in
fact is has 1.8 dBi.
This is very wrong.
Also, over a large GP a 1/2 wave vertical has MORE than a
full "current loop".
No; field strength depends on the current distribution and ohmic loss.Quote:> Funny, It is the same old story...Field
>intensity is proportional to the current flowing......73 "DM"
The question, as posed, is: a 1/2 wave VERTICAL over real ground better or
worse than a 1/2 wave DIPOLE just above real ground?
The answer to this is not obvious; if no one else gets back to you, I'll model
the two and tell you in a couple of days when I can free up a few minutes. My
speculation is that the 1/2 wave vertical, with a good radial system, over real
ground, has the higher f.s.
73
Chip n1IR
by <nhbiw.. » Tue, 26 Oct 1999 04:00:00
the question is not so easy to answer.
Over ideal ground, a ground mounted (insulated) half wave vertical is 1.7
dB over a ground mounted quarter wave. This is because in the case of the
half wave, the "upper" and "lower" part of the sineshape current
distribution add up in phase in some directions.
Over real ground, the situation is more complicated. If one wants to have
high gain into low elevation angles, one must use a very big radial
system. This is because the resultant field strength adds up from a direct
component and a component reflected from the ground. Over real ground,
this reflection is lossy and there is a phase shift. This is in connection
with the so called "pseudo-Brewster" angle. In optics, you observe, using
vertical polarized light, that, under some angle, there will be no
reflection from a horizontal oriented dielectric surface. This is the so
called Brewster angle, where the light enters completely the dielectric
medium. If the medium is lossy, all the light is absorbed. The same is
approximately true for radio waves, with the possible exception, that the
assumption of plane waves does not hold very close to the antenna.
The consequence of this Brewster effect is, that you have to improve the
conductivity of your ground very far away from the antenna. For example if
you want a high gain at 20 Degrees, you must provide a hgh conductive
surface at a distance of (lambda/4)/tan(20 Degress) approx 0.7 * lambda
away from the antenna, assuming that the current loop is at 1/4 lambda.
This is true for the vertical dipole and the base fed as well. Because of
the high impedance of the end fed half wave, a good ground is not
important to increase the efficiency.
Using the above assumptions, I would expect no measurable difference
between the vertical dipole and the base fed half wave vertical.
Slight differences might occur because of a slightly modified current
distribution for the base fed vertical, which is slightly different from
the center fed dipole.
I remember modelling the case of a half wave vertical and a quarter wave
vertical over a ground system consisting of 120 quarter wave radials on
average ground (using a MININEC based program with all the inaccuracies
of MININEC) and found, that the quarter wave was several dB better than
the half wave for low elevation angles. So if I had the space I would put
up a quarter wave vertical over a relatively small (in terms of diameter)
radial system. If you can put up your vertical about one wavelength over
the ground, you can get strong radiation below the brewster angle. This is
because for waves striking a lossy dielectric surface under angles below
the Brewster angle, the waves are reflected with a phase shift of about
180 Degress. The reflectivity can be very high in this case. For this
reason, the waves striking the ground under low angles behave similar to
horizontal polarized waves, so that the "the higher the better" crieria
holds. In this case a halfwave is better than a quarter wave (with same
height of current loop) and a 5/8 wave is little better than a half wave.
In this situation I would expect, that the center fed half wave is
slightly better than the base fed because of the more symmetric current
distribution, but I think that it is not worth the efforts one hat to make
to lead the feedline perpendicular to the antenne for at least one quarter
wave length.
Anyway I am looking forward to the results of simulations; perhaps one of
the people having access to NEC-4 can do this for us.
Vy 73
Ralf
DL 6 OAP
by Richard Harris » Tue, 26 Oct 1999 04:00:00
The ARRL Antenna Book has patterns for perfect earth. We know that the
horizontal dipole would produce a doughnut of radiation around the
center of the wire were it not for the presence of the ground. The
ground`s proximity tends to cancel ground-level energy because
reflection from the ground is out of phase for the horizontal wire. A
horizontal dipole near the ground is mostly a cloud warmer. Between 1/4
and 1/2 wavelength elevation above ground the 1/2-wave dipole produces
radiation at useful angles for communications of several hundred to
maybe a thousand miles. Your mileage may vary. Lossy ground reduces the
radiation amplitude and distinction in the pattern shapes.
The ground reflection of a ground mounted vertical 1/2-wave antenna is
in phase with the radiator. Excellent low-angle radiation results. But,
the 30-degree elevation radiation is much less than that produced from
the horizontal dipole at 1/2-wave elevation. So, if you want to talk 200
to 700 miles, more or less, the horizontal 1/2-wave may be a better
antenna for you. For DX, the vertical 1/2-wave with a good ground system
would be hard to beat.
Best regards, Richard Harrison, KB5WZI
by Gray Frierson Haerti » Tue, 26 Oct 1999 04:00:00
Another way to look at the problem of getting good low angle radiation
from a vertical antenna, is to realize that radiation at low angles
(below 10 or 15 degrees) is going to tend to e*** ground wave
propagation and not spacewave (or skywave) propagation. Over any ground
that you are likely to encounter on this planet (including sea water),
ground wave propagation is pretty lossy at HF. Certainly lossier than
spacewave or skywave propagation.
I believe this is a restatement in different (functional) terms of what
Ralf is getting at in his post which is more descriptive of the physics.
Because of this, I believe that vertical antennas near the earth ar
doomed to mediocre performance at very low radiation angles (at HF).
This is not to say that they make poor antennas. They are capable of
generating very strong skywave signals at angles of 15 to 45 degrees
(depending on length and ground system) and this will grab you lots of
good DX.
However, it is awfully hard to beat a horizontal dipole if is way off
the ground. This is why most of the big gun SWBC stations use
horizontally polarized curtain arrays. Nothing like stacking a bunch of
horizontal dipoles vertically to get you some gain sideways. (c:
Gray
> Dear OM's
> the question is not so easy to answer.
> Over ideal ground, a ground mounted (insulated) half wave vertical is 1.7
> dB over a ground mounted quarter wave. This is because in the case of the
> half wave, the "upper" and "lower" part of the sineshape current
> distribution add up in phase in some directions.
> Over real ground, the situation is more complicated. If one wants to have
> high gain into low elevation angles, one must use a very big radial
> system. This is because the resultant field strength adds up from a direct
> component and a component reflected from the ground. Over real ground,
> this reflection is lossy and there is a phase shift. This is in connection
> with the so called "pseudo-Brewster" angle. In optics, you observe, using
> vertical polarized light, that, under some angle, there will be no
> reflection from a horizontal oriented dielectric surface. This is the so
> called Brewster angle, where the light enters completely the dielectric
> medium. If the medium is lossy, all the light is absorbed. The same is
> approximately true for radio waves, with the possible exception, that the
> assumption of plane waves does not hold very close to the antenna.
> The consequence of this Brewster effect is, that you have to improve the
> conductivity of your ground very far away from the antenna. For example if
> you want a high gain at 20 Degrees, you must provide a hgh conductive
> surface at a distance of (lambda/4)/tan(20 Degress) approx 0.7 * lambda
> away from the antenna, assuming that the current loop is at 1/4 lambda.
> This is true for the vertical dipole and the base fed as well.
> Vy 73
> Ralf
> DL 6 OAP
by William F. Hage » Tue, 26 Oct 1999 04:00:00
> Another way to look at the problem of getting good low angle radiation
> from a vertical antenna, is to realize that radiation at low angles
> (below 10 or 15 degrees) is going to tend to e*** ground wave
> propagation and not spacewave (or skywave) propagation. Over any ground
> that you are likely to encounter on this planet (including sea water),
> ground wave propagation is pretty lossy at HF. Certainly lossier than
> spacewave or skywave propagation.
> I believe this is a restatement in different (functional) terms of what
> Ralf is getting at in his post which is more descriptive of the physics.
> Because of this, I believe that vertical antennas near the earth ar
> doomed to mediocre performance at very low radiation angles (at HF).
> This is not to say that they make poor antennas. They are capable of
> generating very strong skywave signals at angles of 15 to 45 degrees
> (depending on length and ground system) and this will grab you lots of
> good DX.
> However, it is awfully hard to beat a horizontal dipole if is way off
> the ground. This is why most of the big gun SWBC stations use
> horizontally polarized curtain arrays. Nothing like stacking a bunch of
> horizontal dipoles vertically to get you some gain sideways. (c:
> Gray
> > Dear OM's
> > the question is not so easy to answer.
> > Over ideal ground, a ground mounted (insulated) half wave vertical is 1.7
> > dB over a ground mounted quarter wave. This is because in the case of the
> > half wave, the "upper" and "lower" part of the sineshape current
> > distribution add up in phase in some directions.
> > Over real ground, the situation is more complicated. If one wants to have
> > high gain into low elevation angles, one must use a very big radial
> > system. This is because the resultant field strength adds up from a direct
> > component and a component reflected from the ground. Over real ground,
> > this reflection is lossy and there is a phase shift. This is in connection
> > with the so called "pseudo-Brewster" angle. In optics, you observe, using
> > vertical polarized light, that, under some angle, there will be no
> > reflection from a horizontal oriented dielectric surface. This is the so
> > called Brewster angle, where the light enters completely the dielectric
> > medium. If the medium is lossy, all the light is absorbed. The same is
> > approximately true for radio waves, with the possible exception, that the
> > assumption of plane waves does not hold very close to the antenna.
> > The consequence of this Brewster effect is, that you have to improve the
> > conductivity of your ground very far away from the antenna. For example if
> > you want a high gain at 20 Degrees, you must provide a hgh conductive
> > surface at a distance of (lambda/4)/tan(20 Degress) approx 0.7 * lambda
> > away from the antenna, assuming that the current loop is at 1/4 lambda.
> > This is true for the vertical dipole and the base fed as well.
> > Vy 73
> > Ralf
> > DL 6 OAP
> --
> Telecommunications Engineering
> Gray Frierson Haertig & Assoc.
> 820 North River Street, Suite 100
> Portland, Oregon 97227
> 503-282-2989
> 503-282-3181 FAX
by Dennis C. O'Conno » Wed, 27 Oct 1999 04:00:00
In general, there has been a lot of dancing of angels on the head of a pin in
this thread...
Denny
> I believe this is a restatement in different (functional) terms of what
> Ralf is getting at in his post which is more descriptive of the physics.
> Because of this, I believe that vertical antennas near the earth ar
> doomed to mediocre performance at very low radiation angles (at HF).
> This is not to say that they make poor antennas. They are capable of
> generating very strong skywave signals at angles of 15 to 45 degrees
> (depending on length and ground system) and this will grab you lots of
> good DX.
> However, it is awfully hard to beat a horizontal dipole if is way off
> the ground. This is why most of the big gun SWBC stations use
> horizontally polarized curtain arrays. Nothing like stacking a bunch of
> horizontal dipoles vertically to get you some gain sideways. (c:
> Gray
> > Dear OM's
> > the question is not so easy to answer.
> > Over ideal ground, a ground mounted (insulated) half wave vertical is 1.7
> > dB over a ground mounted quarter wave. This is because in the case of the
> > half wave, the "upper" and "lower" part of the sineshape current
> > distribution add up in phase in some directions.
> > Over real ground, the situation is more complicated. If one wants to have
> > high gain into low elevation angles, one must use a very big radial
> > system. This is because the resultant field strength adds up from a direct
> > component and a component reflected from the ground. Over real ground,
> > this reflection is lossy and there is a phase shift. This is in connection
> > with the so called "pseudo-Brewster" angle. In optics, you observe, using
> > vertical polarized light, that, under some angle, there will be no
> > reflection from a horizontal oriented dielectric surface. This is the so
> > called Brewster angle, where the light enters completely the dielectric
> > medium. If the medium is lossy, all the light is absorbed. The same is
> > approximately true for radio waves, with the possible exception, that the
> > assumption of plane waves does not hold very close to the antenna.
> > The consequence of this Brewster effect is, that you have to improve the
> > conductivity of your ground very far away from the antenna. For example if
> > you want a high gain at 20 Degrees, you must provide a hgh conductive
> > surface at a distance of (lambda/4)/tan(20 Degress) approx 0.7 * lambda
> > away from the antenna, assuming that the current loop is at 1/4 lambda.
> > This is true for the vertical dipole and the base fed as well.
> > Vy 73
> > Ralf
> > DL 6 OAP
> --
> Telecommunications Engineering
> Gray Frierson Haertig & Assoc.
> 820 North River Street, Suite 100
> Portland, Oregon 97227
> 503-282-2989
> 503-282-3181 FAX
by Richard Harris » Wed, 27 Oct 1999 04:00:00
A wire doesn`t care how it is e***d. The same current in the same wire
produces the same pattern.
To solve stealth and mechanical problems, maybe we could aim a pencil
thin beam of ionizing radiation at the zenith. We might couple our h-f
energy to this conducting shaft by surrounfing it with a toroid e***d
from our transmitter.
Details yet to be developed.
Best regards, Richard Harrison, KB5WZI
by W6RCecil » Wed, 27 Oct 1999 04:00:00
> Ralf, DL 6 OAP answered the question in the header: "This is true for
> the vertical dipole and the base fed as well."
> A wire doesn`t care how it is e***d. The same current in the same wire
> produces the same pattern.
> To solve stealth and mechanical problems, maybe we could aim a pencil
> thin beam of ionizing radiation at the zenith. We might couple our h-f
> energy to this conducting shaft by surrounfing it with a toroid e***d
> from our transmitter.
> Details yet to be developed.
by pot » Wed, 27 Oct 1999 04:00:00
Cary Vond
> The ARRL Antenna Book has patterns for perfect earth. We know that the
> horizontal dipole would produce a doughnut of radiation around the
> center of the wire were it not for the presence of the ground. The
> ground`s proximity tends to cancel ground-level energy because
> reflection from the ground is out of phase for the horizontal wire. A
> horizontal dipole near the ground is mostly a cloud warmer. Between 1/4
> and 1/2 wavelength elevation above ground the 1/2-wave dipole produces
> radiation at useful angles for communications of several hundred to
> maybe a thousand miles. Your mileage may vary. Lossy ground reduces the
> radiation amplitude and distinction in the pattern shapes.
> The ground reflection of a ground mounted vertical 1/2-wave antenna is
> in phase with the radiator. Excellent low-angle radiation results. But,
> the 30-degree elevation radiation is much less than that produced from
> the horizontal dipole at 1/2-wave elevation. So, if you want to talk 200
> to 700 miles, more or less, the horizontal 1/2-wave may be a better
> antenna for you. For DX, the vertical 1/2-wave with a good ground system
> would be hard to beat.
> Best regards, Richard Harrison, KB5WZI
by Chipn1 » Thu, 28 Oct 1999 04:00:00
With 32 radials, the 1/2 wave vertical has about 0.25 dB more gain than aQuote:>>I'm with KC6UFE...and would add that a full half wave "radiator" is
>>something like 1.5 db stronger in field intensity than a quarter wave
>>"radiator".
>It IS?
>> This is due to a full current "loop" on it versus only a half
>>a current loop on the shorter one.
>That is incorrect. According to this logic, an 1/8 wave, lossless dipole is
>3
>dB below a 1/2 wave lossless dipole.
>According to this logic, an infinitesimal losslessloop has zero dBi, when in
>fact is has 1.8 dBi.
>This is very wrong.
>Also, over a large GP a 1/2 wave vertical has MORE than a
>full "current loop".
>> Funny, It is the same old story...Field
>>intensity is proportional to the current flowing......73 "DM"
>No; field strength depends on the current distribution and ohmic loss.
>The question, as posed, is: a 1/2 wave VERTICAL over real ground better or
>worse than a 1/2 wave DIPOLE just above real ground?
>The answer to this is not obvious; if no one else gets back to you, I'll
>model
>the two and tell you in a couple of days when I can free up a few minutes. My
>speculation is that the 1/2 wave vertical, with a good radial system, over
>real
>ground, has the higher f.s.
>73
>Chip n1IR
Essentially they are the same.
73,
Chip n1IR
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