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There is a lot of discussion lately on how to design a proper tuned input
.... that topic and beer have dominated lately. 16 ways to figure the Q of
the input circuit, 17 ways to tell a really fine beer. I can understand the
value of passing on your knowledge of how to judge a really good beer, but a
tuned input ....why bother.
I built way too many tuned input circuits till I gave it up ... too much
work. I ended up borrowing an approach from the old timers (you here know
who you are) remember swamping. A variation on the old method works for me.
I use a T-PAD attenuator.
The great thing about a T-PAD attenuator is the fact that the load on the
output side can swing a great deal while the input will stay put wonderfully.
Does this sound like whats needed for an input circuit, it does to me. These
transmitting tubes display a fairly large swing in load at different drive
levels, not what your exciter needs to see.
I design the T-PAD for 1db attenuation, nobody needs to loose a lot of drive
power.
I size the resistors (non inductive of course) in each of the three legs to
handle the dissipation and ..... wallah, you have an input circuit that will
show your exciter a nice consistent 50 ohm load. What could be simpler. Its
worked for me for years.
Now we will all hear whats wrong with this approach .... or maybe just some
more great beer theory.
Ron KH6DV
Kaneohe Hawaii
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<HTML><FONT FACE=arial,helvetica><FONT SIZE=2>There is a lot of discussion
lately on how to design a proper tuned input .... that topic and beer have
dominated lately. 16 ways to figure the Q of the input circuit, 17 ways
to tell a really fine beer. I can understand the value of passing on your
knowledge of how to judge a really good beer, but a tuned input ....why bother.
<BR>
<BR>I built way too many tuned input circuits till I gave it up ... too much
work. I ended up borrowing an approach from the old timers (you here know
who you are) remember swamping. A variation on the old method works for
me. I use a T-PAD attenuator.
<BR>The great thing about a T-PAD attenuator is the fact that the load on the
output side can swing a great deal while the input will stay put wonderfully.
Does this sound like whats needed for an input circuit, it does to me.
These transmitting tubes display a fairly large swing in load at
different drive levels, not what your exciter needs to see.
<BR>I design the T-PAD for 1db attenuation, nobody needs to loose a lot of
drive power.
<BR>I size the resistors (non inductive of course) in each of the three legs to
handle the dissipation and ..... wallah, you have an input circuit that will
show your exciter a nice consistent 50 ohm load. What could be simpler.
Its worked for me for years.
<BR>
<BR>Now we will all hear whats wrong with this approach .... or maybe just some
more great beer theory.
<BR>
<BR>Ron KH6DV
<BR>Kaneohe Hawaii
<BR></FONT></HTML>
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