Looking at the N7WS figures, the thing that strikes me is the way the
shunt resistance is increasing on the nichrome resisitors with
frequency. If you model it as a perfect inductor with a constant series
fixed resistance, I guess that is what would happen - Rs stays constant,
but jX goes up. Modelling it as a perfect inductor with a fixed shunt R
is possible, but it strains my credulity a bit. But the series method
provides a model which matches the measurements.
So if the Q isn't to rise with frequency, you need the shunt resistors -
which need to be low inductance -and capacitance.
Hmmm. Doesn't that take away some of the raison d'etre for the nichrome?
Although I can still envisage places where it could be advantageous.
On a different tack, anyone any experience with 4CX1000A's (at HF) and
parasitics?
73
Peter G3RZP
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