Loading Coils; was : Vincent antenna
 

Richard Clark wrote:
On Sun, 02 Dec 2007 22:32:50 GMT, Cecil Moore
wrote:

In what, about 2-4 ns?
No, it increases the VF by roughly 2x in a typical coil.
Why don't you already know that fact?

So, 4-8 nS?

My experience in building coils for base or center loaded verticals was
different. The ratio was close to 1:1 at the base if the replaced
length was not long. The ratio approached 2:1 when the coil was moved
up the vertical, towards the center. It almost did not work if the
coil was moved to the tip of the antenna, or to better say, a coil added
to the tip of the antenna was not an effective way to lower the
resonant frequency.

73, Roger, W7WKB

Loading Coils; was : Vincent antenna
 

AI4QJ wrote:

"Cecil Moore" wrote in message
.net...
Ian White GM3SEK wrote:
My apologies to AI4QJ. He was talking about a parallel R-L circuit, and
my reply was about a series R-L circuit. Each of our statements was
correct in its own context.

Sorry, but your statement is still incorrect. In a
traveling-wave circuit, the current phase varies
every inch along the circuit path. If it didn't,
rhombic antennas wouldn't work.

First, in response to Cecil:

The behaviour of an antenna doesn't depend on how someone chooses to
classify it. You can apply a traveling-wave *model*, but that is merely
your choice of analysis method. It doesn't change anything about how the
antenna actually behaves.

The challenge for Cecil's model is to explain how the antenna does
behave. This cannot be done by reclassifying the type of antenna, or
reclassifying the type of current through the loading coil.

(And please don't drag in yet another irrelevancy about rhombic
antennas. It'll be photons and momentum next.)

AI4QJ continues:
Yes, the total current will have a phase angle somewhere between zero and
ninety degrees. The vector describing the current through the resistor will
be horizontal to the x-axis. The vector describing the current through the
coil will be perpendicular to the x a-xis. The sum of the currents going
into and out of the R-L network will be the vector sum of the R and X(L)
current vectors (Kirchoff's current law) whose magnitude will be the the
hypoteneuse of the triangle formed by R and X(L) sides with an angle
somewhere between zero and 90 degrees.

(My apologies for the wordiness)

No problem about that; we're all thinking out loud about a difficult
subject, so by all means do whatever it takes to get it right.

I think we are in agreement about the basics. One is the boundary
condition that, If the antenna is loaded at a single point by pure
inductance, then by definition there will be zero phase shift in the
current between its terminals.

Practical antennas move away from this boundary condition because the
inductor occupies an appreciable fraction of the physical length, and
begins to behave more like a short section of helically loaded antenna.
In this case we do expect a phase shift in current from end to end of
the inductor, accompanied by radiation from the inductor itself.
However, any valid explanation of practical loading coils must predict
zero phase shift for the boundary condition where the coil displays no
other properties except pure inductance.


--

73 from Ian GM3SEK 'In Practice' columnist for RadCom (RSGB)
http://www.ifwtech.co.uk/g3sek

Loading Coils; was : Vincent antenna
 

Roger wrote:

My experience in building coils for base or center loaded verticals was
different. The ratio was close to 1:1 at the base if the replaced
length was not long. The ratio approached 2:1 when the coil was moved
up the vertical, towards the center. It almost did not work if the
coil was moved to the tip of the antenna, or to better say, a coil added
to the tip of the antenna was not an effective way to lower the
resonant frequency.

73, Roger, W7WKB


This, I assume, was a 1/4 radiator?

Both 1/4 are 1/2?

Regards,
JS

Loading Coils; was : Vincent antenna
 

John Smith wrote:

This, I assume, was a 1/4 radiator?

Both 1/4 are 1/2?

Regards,
JS

are = and--of course ... what can I say, it is late, I am going to bed.

Regards,
JS

Loading Coils; was : Vincent antenna
 

On Dec 2, 10:45 pm, Richard Clark wrote:
On Sun, 02 Dec 2007 22:32:50 GMT, Cecil Moore
wrote:

In what, about 2-4 ns?

No, it increases the VF by roughly 2x in a typical coil.
Why don't you already know that fact?

So, 4-8 nS?

Don't be silly. It decreases the delay from about 50 ns to about 25 ns
in my 75m Texas Bugcatcher coil. The 2-4 ns figure is a wet dream.
--
73, Cecil, w5dxp.com

Loading Coils; was : Vincent antenna
 

On Dec 3, 12:55 am, K7ITM wrote:
Cecil Moore wrote:

In a traveling-wave environment, the phase changes
every inch around the circuit and I can calculate
that phase change...

OK, I live in a very cold environment (freespace) ...

No need for any esoteric stuff. A traveling wave changes one degree
every 1/360 of a cycle. That's just very elementary physics. If the
wavelength is 360 inches, a traveling wave changes one degree per
inch.
--
73, Cecil, w5dxp.com

Loading Coils; was : Vincent antenna
 

On Dec 3, 2:00 am, Ian White GM3SEK wrote:
The challenge for Cecil's model is to explain how the antenna does
behave. This cannot be done by reclassifying the type of antenna, or
reclassifying the type of current through the loading coil.

I'm not reclassifying anything. The differences between traveling-wave
antennas and standing-wave antennas have been known for many decades.
The problem that some of the gurus on this newsgroup have is that they
have forgotten everything they ever knew about standing-waves and
standing-wave antennas. You guys worship your shortcuts to such an
extent that you have completely lost touch with reality. W8JI's 3 ns
delay through a 100T coil on 4 MHz is just one example. At least a few
posters are beginning to understand why W8JI's measurement was
invalid.
--
73, Cecil, w5dxp.com

Loading Coils; was : Vincent antenna
 

AI4QJ wrote:
"Gene Fuller" wrote in message news:25J4j.191181
By the way, saying something is "impossible" is religion, not science. The
distance from one end of the coil to the other is clearly within reach
without violating the speed of light.

But not in 3 nsec. To go from one end to the other end of the 53 foot coil
would be to travel at 53.84E8 m/sec, more than 10 times the speed of light.



So you think an EM wave cannot travel 10 inches in 3 ns? Try again.

You appear to be suffering from the same disease that afflicts Cecil.
Plugging your preferred answer into the calculation might make the
solution easy, but it does not necessarily make it correct.

Since you seem to be somewhat oblivious to what is being debated, let me
restate it.

It is widely accepted that some configurations exhibit a "round and
round the wire mode." Helix antennas and traveling wave tubes fall into
that category.

It is also widely accepted that EM radiation is real, and travels the
speed of light in the appropriate medium.

It is also widely accepted that the "lumped circuit model" is useful in
many configurations.

The entire debate, if all of the personality nonsense is ignored, is
over the appropriate regimes for these "widely accepted" explanations.

Cecil insists that an 80 meter loading coil behaves nearly the same as
one of Corum's quarter-wave resonators. Others believe the coil behavior
is closer to a lumped circuit model.

Your assignment is to do the math to figure out just where in that
spectrum the truth lies.

Hint: "I lags V" is not helpful for the solution.

Good luck!

73,
Gene
W4SZ

Loading Coils; was : Vincent antenna
 

Cecil Moore wrote:
On Dec 3, 2:00 am, Ian White GM3SEK wrote:
The challenge for Cecil's model is to explain how the antenna does
behave. This cannot be done by reclassifying the type of antenna, or
reclassifying the type of current through the loading coil.

I'm not reclassifying anything. The differences between traveling-wave
antennas and standing-wave antennas have been known for many decades.

Oh good! Exactly where do *you* draw the line between them; and why?
Please justify this by giving examples of two antennas that are very
close to your chosen line, but on opposite sides.

Then please justify the difference between your two different
classifications of current.

The problem that some of the gurus on this newsgroup have is that they
have forgotten everything they ever knew about standing-waves and
standing-wave antennas. You guys worship your shortcuts to such an
extent that you have completely lost touch with reality. W8JI's 3 ns
delay through a 100T coil on 4 MHz is just one example. At least a few
posters are beginning to understand why W8JI's measurement was
invalid.

As you are so fond of saying, the technical content of that is duly
noted.


--

73 from Ian GM3SEK 'In Practice' columnist for RadCom (RSGB)
http://www.ifwtech.co.uk/g3sek

Loading Coils; was : Vincent antenna
 

On Dec 3, 7:40 am, Cecil Moore wrote:
On Dec 3, 12:55 am, K7ITM wrote:

Cecil Moore wrote:

In a traveling-wave environment, the phase changes
every inch around the circuit and I can calculate
that phase change...

OK, I live in a very cold environment (freespace) ...

No need for any esoteric stuff. A traveling wave changes one degree
every 1/360 of a cycle. That's just very elementary physics. If the
wavelength is 360 inches, a traveling wave changes one degree per
inch.
--
73, Cecil, w5dxp.com

What a disappointing non-answer, Cecil. I thought you said you can
calculate the phase change in a particular situation, and were willing
to do it. Is the description of the system lacking in some way?

Cheers,
Tom