[TowerTalk] Insulated wire, theory

[Lux, Jim]

On 9/21/22 12:26 PM, Tom Osborne Sr. wrote:
> Can't we just put up an antenna and see where it is resonant and adjust it
> accordingly? 73
> Tom W7WHY

For a dipole or inverted V, esp with a tuner, that works.

If you're doing some sort of multi element array, then you might care more.

And there's the intellectual curiosity  - There's two approaches - one 
is to make some empirical measurements and derive a "correction factor" 
table, for which you don't need to understand "why" it does what it 
does.  The other is to figure out theoretically what's going on, and 
then use that in a modeling code.

The "correction factor" approach probably works pretty well close to 
resonance, but maybe it doesn't work so well at 2x or 3x resonance.



>
> On Wed, Sep 21, 2022, 7:49 AM Lux, Jim <jim at luxfamily.com> wrote:
>
>> On 9/21/22 6:58 AM, Lux, Jim wrote:
>>> A discussion of how NEC4 does insulated wires (in short, by changing
>>> the wave number of the propagation in the conductor) can be found in
>>> the NEC4 Theory Manual.  Search for NEC4TheoryMan.pdf and there's
>>> several copies out there.
>>>
>>>
>>> I suspect that EZNEC does it by a similar approach - changing the
>>> length of the wire to a slightly shorter length to accommodate the
>>> slower propagation in the insulated wire. That may have been done
>>> semi-empirically
>>
>>
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