Mni tnx Rik for
your answer!
No, you didn?t
spoil the fun at all ;-)
I have some
remarks/ideas.
The coil losses
increase linear with the power but not more than linear. So, 10x the power
wouldn?t decrease the antenna efficiency (if no arcing occurs, of course). If
we assume an antenna, e.g. in 8m height with many toploads, then the
efficiency will be poor but the capacitance will be high and thus the needed L
will be small. Therefore we get a low voltage even with very high power and
due to the low efficiency we will keep the legal limit. So, if one has no
possibility to increase the antenna height QRO is one choice, especially when
the operator is already in pension and cannot do a qso in
qrss10000000000000000000000000 any more ;-)
It should be possible to run a
TX directly of the mains (giving about 330V DC). But for 10kW the PSU
current would be 33A, requiring something like a 60000uF/450V elco, these
large HV elco's cost a fortune (at QRL we recenty had to replace a 4700uF/450V
capacitor, it costed over 200 Euro).
And for a Class-D / Class-E amp
running of 330V a 900V power FET might be a bit on the edge for a foolprove TX
(but since you are spending a fortune on elco's you can spend some more money
on 1.5kV devices ;-) ).
Yes, you are right.
But i mean i USA, where the voltage
is 110V, you get about 155V and thus the 900V FET would have 6 times more. For
a class e mode PA, 4x the voltage can be reached when SWR is correct(!) so
there would be a goog savety factor. About the Capacitors: You could reduce
the needed C when using a 3 phase system (of the kitchen oven ;-) ). Then you
would get about 268VDC and therefore a factor 3,35 to the 900V which will be
critical for the FETs when SWR is not absolutely constant 1:1, so better using
a
IXFH24N100 ;-)
Really nice, that
conversation! Tnx!
73, Stefan /
DK7FC
