On Monday, 23 December 2024 17:29:13 -03 Chris KB1NLW via groups.io
wrote:
Until Hans fixes it through programming a lower PA voltage for 160m
and 80m I would recommend against operating or not operating above
10v supply since the PA transistors are actually operating above the
manufacturers rating even with a 1:1 SWR.
Dear Chris,
Allow me to be a little bit confused by your statement.
Are you referring to drain current or maximum power dissipation @ 25°C?
What does the frequency have to do with the operation of the PA if it
outputs into a pure resistive load of 50Ohms? Provided the frequency is
far enough to the lower end of the transit frequency. Which is the case
for 160 and 80m.
People are fine with a SWR of 2:1 or even 3:1 because the resistance,
which the PA is driving, is higher than 50Ohms. BS170 blow when SWR is
high when the resistance is lower than 50Ohms. SWR does not indicate in
which direction the mismatch goes.
73 de
--
Eike Lantzsch KY4PZ / ZP5CGE
