>From several years i'm working with my home made linear amplifier using a
pair of
813 tubes.
It works fine from 10 to 80 running about 500 to 700 watts output. Now I
decide to make an attempt for the 160 m.
So, following two similar articles (QST january 1989 pag. 23 and CQ
november 1997 pag. 30), I add the additional capacitances on the legs of
the PI-network and the additional inductance wounded on Amidon T225A iron
core.
I test with my grid dip the PI-network resonance frequency: it is 1850 Khz.
WOW!
However, when I turn on the amplifier the power output on 160 m band is
only 300 watts!!!
Why? Where is the mistake? Perhaps the RF choke on the plate? or the 500 pF
capacitance (too
small?) between the plates and the PI-network? or the Q of the additional
inductance?
Could you give me some suggestion to improve the performance and understand
the reason why it does'n work as aspected?
TNX and 73 de Aldo IK2ANI
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