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