Steve Hunt wrote:
> Paul,
>
> It's not really counter-intuitive when you remember that at HF the vast
> majority of feedline losses are I*I*R losses and therefore driven by the
> current that is being carried. If we have a 150 Ohm Resistive component
> to the load - no matter what its Reactance - the current into the load
> must be 57.7% that of the matched case when dissipating the same power.
The current could be higher or lower. Say you've got a 150 ohm resistor
in parallel with a 150 ohm inductor. The current that flows through the
inductor also flows through the feedline, and contributes to the loss.
Or, if you've got the resistor and inductor in series. Now the current
flow will be even less. (by a factor of 70%).
that's the difference between apparent power (Irms * Vrms) and active
and reactive power.
> That means that *right adjacent to the load* the feedline power loss per
> unit length will be 1/3 that of the matched case. It's only further back
> along the line, where the current standing wave begins to "develop"
> higher currents, that the losses increase and eventually overtake the
> matched-line losses.
>
> ARRL's TLW software gets it right. Now, if they would just correct their
> hopelessly optimistic loss figures for ladderline, it would be a useful
> programme ;)
>
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