Tom says:
>The primary advantage of nichrome in a suppressor is it lowers the
>HF Q more than it lowers the VHF Q.
I thought the primary advantage was that you could have it get hotter
without the reliability problems of a carbon or MOF resistor!
Of course, if you can guarantee that the layout and lead lengths ensure that
the plate circuit parasitic frequency is below the grid circuit parasitic
frequency, you don't need a parasitic suppressor, because it won't
oscillate.
With things like 572B's with their lengthy grid structures, that's pie in
the sky,
though - at least if you want to go above probabaly 4 MHz. (You'd need the
suppressor, but it only needs to be an inductor, no resistors). I suspect
that is
also the case for 3-500Z's, but maybe with a suitable layout, some of the
ceramic types might get away without suppressors. BTW, how do you
connect to nichrome? Silver (hard) solder, such as Easiflo, with a borax
flux?
What's the permeability of nichrome? That affects the skin depth. It's
surprising (at least to me) how much skin depth can be. For example, the
.0005 inch thick copper foil used in some multilayer PCBs as mid board
ground plane is only 2 skin depths thick at 100 MHz.
73
Peter G3RZP
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