linear loading vs lumped RE: [TowerTalk] SteppIR 40/30

[Jim Lux <jimlux@earthlink.net>]

At 07:11 AM 11/5/2003 -0800, Richard Karlquist wrote:
> > Folding the element does little to reduce the performance. It looks
> > hokie, but it's simple, light weight, more efficient than lumped
> > inductance. The wires have to clear whats underneath but it's a
> >
> > wa3gin
>
> No.  A properly designed lumped inductance is better than linear
> loading.  That's why many 80 meter Yagi owners have upgraded to
> W6ANR's aftermarket loading inductors, replacing the original linear
> loading.  Linear loading is a marketing concept to make you think
> you have eliminated the ohmic losses associated with loading
> coils.  Instead, it *increases* the losses.

I am properly cynical of manufacturer's claims, but I'd be interested in 
some analysis of why linear loading would be better or worse than 
lumped.  It's an interesting question.

With linear loading, there are currents in both the element and the 
loading, and perhaps they are higher, for more IR losses.  There's also 
potentially a change in the current distribution on the element which would 
not only change the pattern, but would also change the IR 
losses.  Intuitively, I would believe that one could build a lower loss 
coil than a linear inductor of the same inductance (because you need fewer 
feet of wire in the coil to get a given inductance, because you have the 
turns squared effect)

Given the remarkably low losses with decent lumped loading, even if the 
linear loading were 10 times greater, it would still probably be 
insigificant compared to the other losses in the entire radiating system 
(except for the few with those hilltop saltwater marshes..)



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