Hello OM's,
in most of the american handbooks they recommend a bifilar choke on a 1/2"
ferrite rod, when the tube's cathode is in direct contact with one side of the
filament or even directly heated. (3-500Z...) The 8877, of course, has no need
for such a choke.
Did anyone check the inductance? What is the permeablility of that ferrite
material?
I want to use a square rod with permeability of about 1000. It is a U/I shaped
material. With 17 bifilar windings on the bottom of the U, I got 24 uH, and
when I close it by using the "I" I measure 230 uH. This is much more then
needed on that point. Should I expect problems? The input of the tube is around
50 Ohms (GS35b).
I have already built a linear, which shows less gain on 160m then on 80m. I am
afraid some input power on 160 is lost in that choke. Unfortunately I did not
check the choke when I made that amp years ago.
Now, I want to avoid that problem in a new desktop project.
Thanks for your comments....Tom, DJ5RE
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