Topband: Hairpin Matching Coil Questions - "Shunt"?

[Tom W8JI]

> Thankyou Charlie.
>
> I got those Q numbers from
> http://www.m0ukd.com/Calculators/air_core_inductor_calculator/
> Maybe a decimal point was left out.

Jim,

I thought something was misleading you somewhere.


Be careful with online calculators. The one in the link uses pi out to 39 
places (which might give the impression of accuracy), but omits many far 
more critical, important, parameters. It is a very rough guess that might be 
a mile off, even though the publisher implies accuracy. They would be better 
off to just use "3.1" for Pi, and add in some more important things.

One way to evaluate an inductor calculator for design omissions is to see if 
it asks for:

1.) Insulation thickness and type
2.) Turns spacing
3.) Form material
4.) Conductor size
5.) Form length
6.) Form diameter

That one  grossly fails. It doesn't ask for several important things.


To check the calculator for function, start taking a large coil up higher in 
frequency. If you get weird results like progressively increasing Q that 
goes over 1000 for normal good conductors, extreme inductance values (like 
values near whole Henries at HF and higher), the calculator is likely just 
junk.

That one completely fails. It obviously does not consider turn-to-turn 
capacitance, skin effect, materials, or internal resonances, because I can 
"make" door bell wire inductors with Q's in the thousands and almost a Henry 
of inductance on 50 MHz!!

Since it doesn't ask for enough things and obviously ignores many important 
traits of inductors, it is unreliable. It might work in some cases by pure 
luck, but who knows when it could be trusted!!

Things like that can send you down the wrong path, and cause you to start 
giving out wrong numbers.

73 Tom