> Seems that issue is not that effective resistivity of nichrome increases
> with decreasing frequency - I don't think anybody is arguing that. What is
> evident is that the effective series resistance of the nichrome suppressor
> is higher than conventional suppressor at low frequencies. From what I can
> see, this seems to be the basic tradeoff between the nichrome suppressors
> and the conventional suppressors. If I am recalling the test data
> correctly, the nichrome suppressor has higher losses at moderate VHF
> frequencies (50 to 100 MHz) - a good thing, at the expense of higher
> losses in the HF frequency range (a bad thing). As the frequency increases
> further the the two suppressors start to converge as the inductive
> reactance of the nichrome suppressor starts to dominate over the
> resistance of the wire. No rocket science here.
The AL80B becomes unstable, with no suppressor, at around 180
MHz or so depending on the tube socket and lead length.
Suppressor operation at 150-200 MHz is all that matters in that
case.
The Measures' suppressor Wes tested was NOT the suppressor
Rich sells. Wes duplicated the AL-80 suppressor out of nichrome
and measured it. The actual suppressor Rich sells has lower Rp
than the stock suppressor.
When the "production" nichrome suppressor is installed in the
anode system, anode system Q increases except at HF and lower
VHF....where it decreases (and where you don't want it to
decrease).
73, Tom W8JI
w8ji@contesting.com
--
FAQ on WWW: http://www.contesting.com/FAQ/amps
Submissions: amps@contesting.com
Administrative requests: amps-REQUEST@contesting.com
Problems: owner-amps@contesting.com
|