linear loading vs lumped RE: [TowerTalk] SteppIR 40/30
Jim Lux
jimlux at earthlink.net
Wed Nov 5 09:54:21 EST 2003
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..)
More information about the TowerTalk
mailing list