"Keith Dysart" wrote in message
...
On Dec 5, 10:40 am, Cecil Moore wrote:
Keith Dysart wrote:
Hardly surprised. After all, the same can be achieved with an
inductor and/or capacitor which has essentially
0 physical (or electrical) length.

Only true for a lumped inductor which doesn't exist
in reality. Any large coil, such as the coil tested
by W8JI, has considerable electrical length at 4 MHz.
This electrical length is what some folks have been
denying for years even though they should certainly
know better by now.

This then begs the question, is the physical (or electrical) phase
shift in the components of much interest?

It is - when someone tries to convince the world that
there is a 3 ns delay through a 2" dia, 10 TPI,
100 turn coil. The electrical length (phase shift)
through a coil is necessary and sufficient to kill
the old wives tales being supported by some so-called
"experts" on this newsgroup.

But again, given that the key message is "that the system phase shift
is NOT equal to the sum of the phase shifts of the components.",
why is the question of delay through the coil important?

Is it just to have a "debate" with some called experts?

Or does it offer some advancement in the solution of antenna
problems? Having computed (or measured) the delay through
the coil, how would this alter the design of the antenna?

...Keith


That train of arguments and nitpicking developed from the main argument
about distribution of (standing wave) current along the loading coil and
antenna.
"Gurus" and some literature claimed that current is the SAME at both end of
the coil (Kirchoff "said so"). That would mean that current remains constant
along the coil and then drops drastically towards (almost) zero at the tip.
This makes loaded whip antenna look better than it is.

The reality is that current drops around 40 - 60 % along the loading coil,
which makes the distribution along the remaining stinger starting with less
and overall efficiency less.

The key to understand the loaded radiator is to trying to maximize the
current in the physical "straight wire" - so the higher the coil, larger
hat, will stretch the high current portion of the radiator and make it more
efficient. Fooling yourself by modeling the loading coil as a lumped
inductance and making it look better in modeling program does not help.
Again, this effect is magnified in multi element loaded arrays, so while
some might consider this not a big deal in a mobile whip, the errors would
magnify in multielement designs.

I hope I can get the main "problem" across, the rest was digging into the
smaller effects like coil radiates, junction impedance discontinuity, bla,
bla....

Now I also understand the small "bump" increase in the current at the bottom
of the coil due to some loses that reflected wave encounter on the way
"there and back" to the tip of the radiator from the bottom of the coil (?)

73 Yuri, www.K3BU.us