Topband: 160 metre vertical with 'top loading'
Guy Olinger K2AV
olinger at bellsouth.net
Mon Apr 25 11:38:43 PDT 2011
I think it would be good to do Yuri's famous picture with a coil of
identical inductance, but that is evenly wound around a T300A-2 iron
powder toroid, or the smallest that can create the inductance.
I don't think the actuality is nearly as simple as the opposite
arguments. If the coil is spread out so that the field of the first
turn does not substantially encompass the last turn, then substantial
differences will occur in the current because it's acting more like a
miscellaneous wire, and modeling with separate inductors is more
accurate, and the length is the issue. This would be the case in
Yuri's picture with two RF ammeters on either end of a long piece of
But, if the field of the first turn completely encompasses the last
turn, as in a fully covering winding on a powdered iron toroid, or
tight layered turns on ferrite core forms, and cannot be affected by
other close fields (like the antenna wire itself) then the fields and
currents are substantially forced into self-compliance across the
These are opposites. Neither all length or all lump will work
properly as the physical details will determine where a given winding
falls on a scale between all lump and all length. This is the same
kind of issues that occur getting into VHF where capacitors become RLC
networks, and you can't use caps in a VHF circuit unless you know the
RLC of a cap and account for it in the circuit. Ditto with all wires
are now inductors, etc.
Once one understands this irritating detail, there are situations
where coil stock and wound toroids each display advantages that may
recommend one or the other.
I think it very unfortunate that the demonizing and name-calling of
our current political climate has worked its way into science. It
destroys possibilities in both politics and science.
If two responsible experimenters get opposite results in what on
surface are identical experiments, THERE IS A REASON, which means
THERE IS AN OPPORTUNITY TO DISCOVER AND ADVANCE. It does no good at
all for the owners of the different results to accuse the other of
using satanic rituals to obtain their results.
On Sun, Apr 24, 2011 at 9:47 PM, <k3bu at optimum.net> wrote:
>> On the eternally recurring argument about current into and out
>> of a loading coil, here is the way my simple mind has always
>> understood it:
>> W8JI is correct in that the current into a perfect inductor must
>> equal the current out of it. It's a piece of coiled wire so
>> where else can the current go? Tom's assumption here is a
>> 'perfect' inductor with no distributed capacitance.
> He is not correct!
> Have you looked at the "piece" of wire - quarter wave antenna, having the max current at the base and ZERO at the tip? And voltage low at the base and high at the tip - corona?
> Where did the current go?
> It is the STANDING WAVE circuit, with superimposed forward and reflected RF currents creating cosinusoidal distribution ALONG the wire and not the DC circuit.
> Why is it hard so understand that if current can vary along the straight wire, it can wary along the coiled wire too?
> Yuri K3BU.us
>> K3BU is also correct because he is assuming a practical
>> inductor, with a finite length and distributed capacitance to
>> ground. That's where the missing current is going, through the
>> distributed capacitance to ground and hence lower output current
>> from the top of the inductor into the antenna.
>> Both right, so why the disagreement?
>> Tom G3OLB
>> UR RST IS ... ... ..9 QSB QSB - hw? BK
> UR RST IS ... ... ..9 QSB QSB - hw? BK
More information about the Topband