RadioBanter - View Single Post - Current in antenna loading coils controversy

November 2nd 03, 10:14 PM

On 02 Nov 2003 18:40:25 GMT, oSaddam (Yuri Blanarovich)
wrote:

|N7WS:
|
|I used MultiNEC to invoke EZNEC for all calculations. I modeled a
|shorter-than-quarter-wavelength vertical, loaded with an inductor, all
|of this over perfect ground.
|
|How did you model inductor, as physical zero length inductance?

Yes.

|Did you try substituting (coil) inductor with equal inductance loading stub?

Yes. No difference.

|Did you try one of the situations (band, antenna/coil size) that W9UCW
|describes in his measurements?

No. I only skimmed the other web sites. Didn't see anything there to
make me change my mind. A couple of ammeters separated by 10% of the
radiator length doesn't work for me. Might as well put one at the
bottom and one at the top.

|He used almost "perfect" ground of 60 radials for measurement. Results will be
|offest by some amount due to varying ground conditions (at very low angles),
|but in the same way and this is not the subject of the argument.

Perfect ground is perfect. Any number of radials doesn't approach
perfect ground.

|
|The current actually peaks at the inductor;
|in other words, the highest current point on the structure is at the
|inductor.
|
|That's what W8JI calculated in EZnec, does it make sense?

Yes.

|Like 2+2 is 4.5? Why
|would inductor "suck" the current up?

It doesn't "suck it up." Haven't you ever hear of circulating
current?

|We should then use "those" inductors to
|suck the current all the way to the top of the whip - perfect antenna?
|Cecil, can you 'splain that?
|
|3) For a give length radiator, gain is unaffected by where the
|inductor is located along the length of the radiator and by inductor
|Q.
|
|(If the inductor is zero length?)

Yes

|This should be huge screaming flag that there is something drastically wrong
|with your whole approach. Look at any mobile shootout results and you will see
|10 - 20 dB differences, ask Cecil, he wittnessed them.

Remember...perfect ground. Mobile antennas have almost no ground.
|
|Looks like we exhausted reasoning, facts, measurements, found what we wanted,
|unless there is breakthrough in capturing the effect in modeling software we
|are at the end of the rope.

My results compare more closely with Hansen's than anything else I've
seen put forward. I rest my case.

Wes Stewart N7WS

Later, I'm back to NASCAR at PIR.