Dear All. I am having problems
with the choice of
material for the output network of the 475kHz Valve TX.
The
network is an L – C – L, ‘T’ network with an input
impedance of 2100 ohms and a load of 50 ohms, for this configuration
the input
L is 7.7mH, shunt capacitance is 117pf, and output L is 1.1mH. The PA
design
using a 6146 low power or 813 high power work fine when simulated using
LT
spice IV. When testing in the real world using the 6146 there is in
excess of
800v rms rf on the network side of the anode coupling capacitor, but
nothing
after the input L. I can only conclude that I using the wrong type
material for
the toroids, I used the largest size (unmarked) toroid which gave me a
modest
number of turns. I have checked the Amidon tables and Iron Powder
because of
the low AL
values, which leaves Ferrite, which mix would you recommend? The
simulations
give me output powers 90W for the 6146, and 300W for the 813. I would
be
grateful for any core material advice .
Ken Wright.
M0KHW
