Dish reflector
 

Art Unwin wrote:
What if one put a diode in that ground line?

Then it would no longer be linear to RF. Seems
to me, it would generate some industrial grade
harmonics.
--
73, Cecil, IEEE, OOTC, http://www.w5dxp.com

Dish reflector
 

"Art Unwin" wrote in message
...

What if one put a diode in that ground line?

you thought you had noise before?? try putting in the diode and see what you
get!

Dish reflector
 

On Apr 19, 10:09*am, Richard Fry wrote:
On Apr 19, 8:09*am, Cecil Moore wrote: To make matters even worse: I had a similar problem
with drooping 1/4WL radials DC insulated from the tower.
The drooping radials coupled RF into the tower and
turned it into a radiator which screwed, oops, I
mean skewed the radiation pattern upwards.

________________

Some designs use drooping radials to reduce the vertical angle of the
peak radiation launched by the monopole section.

But that is a conclusion made for an infinite distance, with
consideration of the propagation environment on the intrinsic pattern
launched by the monopole, and the height of the monopole + its
elevated radials above the earth.

The link below leads to paste-up of NEC screens showing the
performance of a monopole driven against four 1/4-wave, essentially
horizontal radials. *The entire system is isolated from earth ground.

The driving impedance, the elevation pattern shape, and the peak gain
are close to "textbook" values for a 1/4-wave monopole driven against
a perfect ground plane.

A form of this design is being used with good success in the AM
broadcast industry -- where using a conventional, buried-radial ground
system is impractical due to rocky terrain.

The groundwave performance of these systems shows that their intrinsic
gain is maximum in the horizontal plane, and very close to the
theoretical value of 5.15 dBi.

http://i62.photobucket.com/albums/h8...WithElevatedRa...

RF

Dish reflector
 

Roy Lewallen wrote:
I measured current, which as everyone with a Novice or higher grade
license should know is the rate of flow of charge(*). The charge flows
in one direction during each half cycle, and in the other during the
other half cycle, resulting in current which is positive for half the
cycle and negative for the other.

Actually, electrons in a wire are slow-moving particles
and tend to oscillate back and forth at RF frequencies
rather than "flowing".

But what is being discussed here is the total current
reported by EZNEC. Is EZNEC wrong when it indicates
1 degree of current phase shift in 30 degrees of
length in a dipole antenna?
--
73, Cecil, IEEE, OOTC, http://www.w5dxp.com

Dish reflector
 

Cecil Moore wrote:
Roy Lewallen wrote:
I measured current, which as everyone with a Novice or higher grade
license should know is the rate of flow of charge(*). The charge flows
in one direction during each half cycle, and in the other during the
other half cycle, resulting in current which is positive for half the
cycle and negative for the other.

Actually, electrons in a wire are slow-moving particles
and tend to oscillate back and forth at RF frequencies
rather than "flowing".

But what is being discussed here is the total current
reported by EZNEC. Is EZNEC wrong when it indicates
1 degree of current phase shift in 30 degrees of
length in a dipole antenna?

What 30 degrees? There aren't any "30 degrees of length"
in a loading coil, and there doesn't have to be.
Cecil, repeating your fantasies over and over again don't
make them true.
73,
Tom Donaly, KA6RUH

Dish reflector
 

Tom Donaly wrote:
Cecil Moore wrote:
But what is being discussed here is the total current
reported by EZNEC. Is EZNEC wrong when it indicates
1 degree of current phase shift in 30 degrees of
length in a dipole antenna?

What 30 degrees? There aren't any "30 degrees of length"
in a loading coil, and there doesn't have to be.

I'm glad you asked, Tom. There was no mention of
a loading coil. I am talking about a simple 1/2WL
wire dipole with current probes at the x=1/3 and
y=2/3 points as illustrated. Why I am doing that
will become obvious.

------------------------fp-------x-------y--------

This is a center-fed 1/2WL dipole with current probes
installed at points 'x' and 'y'. The 1/2WL dipole is
known to be 180 degrees long. Half of a 1/2WL dipole
is 1/4WL, i.e. 90 degrees long. From the feedpoint
to point 'x' is 30 degrees. From point 'x' to point
'y' is 30 degrees. From point 'y' to the end of the
dipole is 30 degrees.

This 1/2WL dipole in EZNEC uses two wires of 90 segments
each, i.e. each segment equals one degree of dipole.
Point 'x' is at segment 30 and point 'y' is at segment
60 in Wire No. 2 on the right side of the dipole above.

Here are the results directly from EZNEC:

Source 1 Current = 1 A. at 0.0 deg.

Wire No. 2:
Segment Conn Magnitude (A.) Phase (Deg.)
30 'x' .87634 -1.49
60 'y' .52573 -2.43
90 Open .01185 -3.12

The phase of the current changes by 1.06 degrees between
point 'x' and point 'y' which is 30 degrees of antenna
*WIRE* (not loading coil). How can the phase of that current
possibly be used to determine the delay through the wire
which we know is related to the speed of light in the wire
medium? The delay through 30 degrees of wire at 4 MHz
would be about 20 nanoseconds.

In the 1/2WL wire dipole above, the phase of the current
in each 90 degrees of wire changes by 3.12 degrees.

If Roy performs the measurements, he will correctly report
a negligible phase shift in the current between point 'x'
and point 'y' (just as he did for the loading coil).

Following his previous loading coil logic, he will report
that the delay through 30 degrees of wire dipole is not
20 nS at 4 MHz as would be expected but is instead closer
to zero, maybe one or two nanoseconds. We all know that
report would be false. One cannot use a current with
essentially unchanging phase to calculate delay through
a wire (or through a loading coil).

If Roy cannot accurately measure the delay through
30 degrees of wire, why does anyone suppose Roy can
accurately measure the delay through a loading coil
using the phase of that same total current on a standing
wave antenna?

Note that the true phase information is contained in the
amplitude, not the phase, just as Gene Fuller said. If we
take the ARCCOSine of the magnitudes above, we obtain:

Source, ARCCOS(1.0) = 0 degrees
Seg 30, ARCCOS(0.87634) = 29 degrees
Seg 60, ARCCOS(0.52573) = 58 degrees
Seg 90, ARCCOS(0.01185) = 89 degrees

Incidentally, I told all of this to Roy 5 years ago,
Jan 2004, according to Google. He plonked me.
--
73, Cecil, IEEE, OOTC, http://www.w5dxp.com

Dish reflector
 

Cecil Moore wrote:
Tom Donaly wrote:
Cecil Moore wrote:
But what is being discussed here is the total current
reported by EZNEC. Is EZNEC wrong when it indicates
1 degree of current phase shift in 30 degrees of
length in a dipole antenna?

What 30 degrees? There aren't any "30 degrees of length"
in a loading coil, and there doesn't have to be.

I'm glad you asked, Tom. There was no mention of
a loading coil. I am talking about a simple 1/2WL
wire dipole with current probes at the x=1/3 and
y=2/3 points as illustrated. Why I am doing that
will become obvious.

------------------------fp-------x-------y--------

This is a center-fed 1/2WL dipole with current probes
installed at points 'x' and 'y'. The 1/2WL dipole is
known to be 180 degrees long. Half of a 1/2WL dipole
is 1/4WL, i.e. 90 degrees long. From the feedpoint
to point 'x' is 30 degrees. From point 'x' to point
'y' is 30 degrees. From point 'y' to the end of the
dipole is 30 degrees.

This 1/2WL dipole in EZNEC uses two wires of 90 segments
each, i.e. each segment equals one degree of dipole.
Point 'x' is at segment 30 and point 'y' is at segment
60 in Wire No. 2 on the right side of the dipole above.

Here are the results directly from EZNEC:

Source 1 Current = 1 A. at 0.0 deg.

Wire No. 2:
Segment Conn Magnitude (A.) Phase (Deg.)
30 'x' .87634 -1.49
60 'y' .52573 -2.43
90 Open .01185 -3.12

The phase of the current changes by 1.06 degrees between
point 'x' and point 'y' which is 30 degrees of antenna
*WIRE* (not loading coil). How can the phase of that current
possibly be used to determine the delay through the wire
which we know is related to the speed of light in the wire
medium? The delay through 30 degrees of wire at 4 MHz
would be about 20 nanoseconds.

In the 1/2WL wire dipole above, the phase of the current
in each 90 degrees of wire changes by 3.12 degrees.

If Roy performs the measurements, he will correctly report
a negligible phase shift in the current between point 'x'
and point 'y' (just as he did for the loading coil).

Following his previous loading coil logic, he will report
that the delay through 30 degrees of wire dipole is not
20 nS at 4 MHz as would be expected but is instead closer
to zero, maybe one or two nanoseconds. We all know that
report would be false. One cannot use a current with
essentially unchanging phase to calculate delay through
a wire (or through a loading coil).

If Roy cannot accurately measure the delay through
30 degrees of wire, why does anyone suppose Roy can
accurately measure the delay through a loading coil
using the phase of that same total current on a standing
wave antenna?

Note that the true phase information is contained in the
amplitude, not the phase, just as Gene Fuller said. If we
take the ARCCOSine of the magnitudes above, we obtain:

Source, ARCCOS(1.0) = 0 degrees
Seg 30, ARCCOS(0.87634) = 29 degrees
Seg 60, ARCCOS(0.52573) = 58 degrees
Seg 90, ARCCOS(0.01185) = 89 degrees

Incidentally, I told all of this to Roy 5 years ago,
Jan 2004, according to Google. He plonked me.

I don't blame him for plonking you. You're saying that because you
fantasized that Roy would make a mistake that Roy would never make,
that he also made the same mistake when measuring the delay through a
coil. Cecil, a length of antenna is not a coil. A coil is not an
antenna. Declaring that coils are antennas and vice versa doesn't make
them so. You don't really know what the delay through your bugcatcher
coil is. If you substituted a real transmission line for your coil,
you could make the degree length - within limits - whatever you wanted
it to be just by changing the Z0 of the transmission line.

So here's your logic: Because EZNEC reports a amall angular difference
at the ends of your half-wave antenna in current, and because Roy
measured a small difference in delay through a coil, there must be a
larger real delay across the coil due to the analogy with the half wave
antenna. You're assuming, without proof, that the coil behaves as a
piece of straight wire, therefore the coil behaves as a piece of
straight wire. Nice logic. You have a lot in common with Art.
73,
Tom Donaly, KA6RUH

Dish reflector
 

On Apr 20, 2:29*pm, "Tom Donaly" wrote:
Cecil Moore wrote:
Tom Donaly wrote:
Cecil Moore wrote:
But what is being discussed here is the total current
reported by EZNEC. Is EZNEC wrong when it indicates
1 degree of current phase shift in 30 degrees of
length in a dipole antenna?

What 30 degrees? There aren't any "30 degrees of length"
in a loading coil, and there doesn't have to be.

I'm glad you asked, Tom. There was no mention of
a loading coil. I am talking about a simple 1/2WL
wire dipole with current probes at the x=1/3 and
y=2/3 points as illustrated. Why I am doing that
will become obvious.

------------------------fp-------x-------y--------

This is a center-fed 1/2WL dipole with current probes
installed at points 'x' and 'y'. The 1/2WL dipole is
known to be 180 degrees long. Half of a 1/2WL dipole
is 1/4WL, i.e. 90 degrees long. From the feedpoint
to point 'x' is 30 degrees. From point 'x' to point
'y' is 30 degrees. From point 'y' to the end of the
dipole is 30 degrees.

This 1/2WL dipole in EZNEC uses two wires of 90 segments
each, i.e. each segment equals one degree of dipole.
Point 'x' is at segment 30 and point 'y' is at segment
60 in Wire No. 2 on the right side of the dipole above.

Here are the results directly from EZNEC:

Source 1 * * *Current = 1 A. at 0.0 deg.

Wire No. 2:
Segment *Conn * * *Magnitude (A.) *Phase (Deg.)
30 * * * 'x' * * * *.87634 * * * * *-1.49
60 * * * 'y' * * * *.52573 * * * * *-2.43
90 * * * Open * * * .01185 * * * * *-3.12

The phase of the current changes by 1.06 degrees between
point 'x' and point 'y' which is 30 degrees of antenna
*WIRE* (not loading coil). How can the phase of that current
possibly be used to determine the delay through the wire
which we know is related to the speed of light in the wire
medium? The delay through 30 degrees of wire at 4 MHz
would be about 20 nanoseconds.

In the 1/2WL wire dipole above, the phase of the current
in each 90 degrees of wire changes by 3.12 degrees.

If Roy performs the measurements, he will correctly report
a negligible phase shift in the current between point 'x'
and point 'y' (just as he did for the loading coil).

Following his previous loading coil logic, he will report
that the delay through 30 degrees of wire dipole is not
20 nS at 4 MHz as would be expected but is instead closer
to zero, maybe one or two nanoseconds. We all know that
report would be false. One cannot use a current with
essentially unchanging phase to calculate delay through
a wire (or through a loading coil).

If Roy cannot accurately measure the delay through
30 degrees of wire, why does anyone suppose Roy can
accurately measure the delay through a loading coil
using the phase of that same total current on a standing
wave antenna?

Note that the true phase information is contained in the
amplitude, not the phase, just as Gene Fuller said. If we
take the ARCCOSine of the magnitudes above, we obtain:

Source, ARCCOS(1.0) * * = *0 degrees
Seg 30, ARCCOS(0.87634) = 29 degrees
Seg 60, ARCCOS(0.52573) = 58 degrees
Seg 90, ARCCOS(0.01185) = 89 degrees

Incidentally, I told all of this to Roy 5 years ago,
Jan 2004, according to Google. He plonked me.

I don't blame him for plonking you. You're saying that because you
fantasized that Roy would make a mistake that Roy would never make,
that he also made the same mistake when measuring the delay through a
coil. Cecil, a length of antenna is not a coil. A coil is not an
antenna. Declaring that coils are antennas and vice versa doesn't make
them so. You don't really know what the delay through your bugcatcher
coil is. If you substituted a real transmission line for your coil,
you could make the degree length - within limits - whatever you wanted
it to be just by changing the Z0 of the transmission line.

So here's your logic: Because EZNEC reports a amall angular difference
at the ends of your half-wave antenna in current, and because Roy
measured a small difference in delay through a coil, there must be a
larger real delay across the coil due to the analogy with the half wave
antenna. You're assuming, without proof, that the coil behaves as a
piece of straight wire, therefore the coil behaves as a piece of
straight wire. Nice logic. You have a lot in common with Art.
73,
Tom Donaly, KA6RUH

Well Tom I am not part of this debate but to say a coil is not a
radiator is silly It must radiate as does a helix antenna. The only
difference is how much slower the helix forces the charge to delay as
in "slow wave." Thus the coil act as a radiator where you must
multiply it by a velocity factor. After all, a "tesla" style coil will
display a resonance with the wire used much longer than a straight
wire length and like a helix will radiate.
Kraus states that for a helix one should not use wire shorter than two
wavelength
which I suspect is a substitute calculation for the VF change from a
straight radiator.

Ar

Dish reflector
 

Tom Donaly wrote:
I don't blame him for plonking you. You're saying that because you
fantasized that Roy would make a mistake that Roy would never make,
that he also made the same mistake when measuring the delay through a
coil.

Sorry Tom, that is a diversion. The subject is NOT the delay
through a coil. The present subject is the delay through a
straight wire which is well understood. Please deal with the
topic at hand. If you refuse, we will know that you are not
sincere as far as technical facts are concerned.

Please ask Roy to prove that the current on a standing wave
antenna can be used to measure the delay through a straight
piece of wire that is x degrees long. If so, exactly how is
it done?

Roy is NOT omniscient. He definitely made the mistake but
like most gurus, refuses to admit it. You want to sweep the
mistake under the rug through diversions but I won't allow
you to do that. Once you and Roy admit that the current on
a standing wave antenna cannot be used to calculate delay,
everything else will become clear.

Please feel free to contact Roy by private email to resolve
the issue. Roy has, so far, simply stuck his head in the
sandbags and refused to respond. I'm sure he would have
advised you to plonk me instead of engaging me, for fear
of being proved wrong.

Yet, he admitted years ago that the phase of current in a
standing wave antenna varies by a very small amount. He
is presently trying to have his cake and eat it too. In
the process, he (and you as a supporter) are hoodwinking
the unwashed masses. Shame on all of you.
--
73, Cecil, IEEE, OOTC, http://www.w5dxp.com

Dish reflector
 

Art Unwin wrote:
Kraus states that for a helix one should not use wire shorter than two
wavelength which I suspect is a substitute calculation for the VF
change from a straight radiator.

Because of adjacent coil coupling, it takes
more wire to achieve the phase shift effect
of a straight wire.
--
73, Cecil, IEEE, OOTC, http://www.w5dxp.com