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Old April 29th 06, 03:19 PM posted to rec.radio.amateur.antenna
 
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Default Missing Degrees in Mobile Antennas?


Cecil Moore wrote:
wrote:
Hanging his hat on Cecil, but now Cecil is getting the picture and
yanking the rug out from under Yuri and his "missing electrical degree
cutrrent taper and phase shift theory".


Is the purpose of this newsgroup to smear individuals or to
get to the technical facts?


I don't know. You and Yuri seem to be playing that game as much or more
than anyone else. It's tough for both sides to behave and anyone to
learn anything when all this strange stuff goes on, but this thread (in
various forms) is very similar to the famous Fractenna threads.


Nobody is 100% correct 100% of
the time.


.....and that obviously includes you as well as the rest of us. The key
is to speak like friends and be honest rather than make this stuff
into a long "Fractenna" thread.

The coil still occupies tens of degrees and still
suffers a current taper because of that delay.


The coil does NOT have to occupy tens of degrees nor does it have to
provide any current phase delay from end to end. It does have to have
SOME delay and some current taper since it occupies space, but it can
be so small we can't reliably measure it.

The phase delay and current taper is tied to the load impedance on the
open end of the coil and the construction of the coil, not to the
electrical degrees. It appears you know that now.

It only took three or four years, but at least that's better than
Fractenna. :-)


I wouldn't laugh just yet, Tom. There's plenty of misconceptions
on both sides.


My opinion is Lewallen and maybe a dozen others have a good handle on
how it works. It appears you have gradually came more to center also,
but I'm not quite positive how far. At least you no longer apperar to
be saying the coil represents missing electrical degrees.

The delay through the loading coil is still tens of
degrees, not anywhere close to the near-zero degrees that you have
been asserting for years.


Be careful there. I have NOT been asserting that for years. My initial
assertions years ago was there was no delay, but that was because I
considered the inductor an inductance and was speaking of an
inductance. Over two or three years ago I posted this:

http://www.w8ji.com/mobile_and_loaded_antenna.htm

which explains it is a matter of stray capacitance to the outside world
compared to load inmpedance terminating the coil that causes deviations
from a "perfect" coil.

I also measured antenna current and posted the results at:

http://www.w8ji.com/mobile_antenna_c...ts_at_w8ji.htm


The delay through a typical 75m bugcatcher
coil appears to be about ~35 degrees with ~11 degrees of stinger.
The "missing" ~44 degrees occurs at the impedance discontinuity
between the coil and the stinger just as it does in my 450/50 ohm
stub example.


I'd bet money I can build a coil that has very low phase delay. I'd
also bet I could build one with larger phase delay **at the same point
and frequency in the same system**.

The problem is one of the stray capaciatnce from the coil to the
outside world compared to terminating impedance of the coil.

The 3 nS delay measured by you and the undetectable delay
measured by W7EL were invalid measurements of delay.



So you say. We have only your opinion or view on that, and that
dosagrees with other people's opinions. You are not the final word.

Standing wave current suffers zero delay all along a 1/2WL
dipole whether it be in a wire or in a coil. The delay through a
typical mobile loading coil on 4 MHz appears to be about 25 nS
about half of what one would get in a straight wire equal to the
wire used in the coil.


Again it depends on the form factor of the coil. By altering the coil
with no other changes it can be made to vary quite a bit.

73 Tom