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[AMPS] 4-1000A Project

To: <amps@contesting.com>
Subject: [AMPS] 4-1000A Project
From: DF3KV@aol.com (DF3KV@aol.com)
Date: Tue, 3 Apr 2001 20:38:16 EDT

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na9d@mindspring.com: wrote


> Why do you need a good bandswitch to prevent arcing at high voltages?
> 
> 
Jon,

With higher HT at the anode you get a higher ouput impedance RL, therefore 
the resulting RF voltage over the tank.circuit, no DC as it is blocked,  gets 
higher at the same output and even higher if you make use of the better gain 
which results in  more output at a given drive.
Your tank-circuit  needs less L  and it becomes very likely that shorted 
turns 
act as tesla coils causing arcs through the bandswitch if distances between
contacts are not wide enough.

So far I have no experience with the 4-1000 which is comparable 
to the QB5/1750 which I use in a couple of homebrew amps.
But I have used both, QB4/1100 and 4-400, in my modified L-4B.
There was no difference in gain with both types ( 12-13db ) at 4KV, so 
probably the 4-1000 being in the same family, will amplify likewise with
anode voltages between 4.5 and 5KV. 

Measurement equipment here are Bird and R&S wattmeters + scope .

73, Peter







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<HTML><FONT FACE=arial,helvetica><FONT  SIZE=2>
<BR>
<BR>
<BR>na9d@mindspring.com: wrote
<BR>
<BR>
<BR><BLOCKQUOTE TYPE=CITE style="BORDER-LEFT: #0000ff 2px solid; MARGIN-LEFT: 
5px; MARGIN-RIGHT: 0px; PADDING-LEFT: 5px">Why do you need a good bandswitch to 
prevent arcing at high voltages?
<BR>
<BR></BLOCKQUOTE></FONT><FONT  COLOR="#000000" SIZE=3 FAMILY="SANSSERIF" 
FACE="Arial" LANG="2">
<BR>Jon,
<BR>
<BR>With higher HT at the anode you get a higher ouput impedance RL, therefore 
<BR>the resulting RF voltage over the tank.circuit, no DC as it is blocked, 
&nbsp;gets 
<BR>higher at the same output and even higher if you make use of the better 
gain 
<BR>which results in &nbsp;more output at a given drive.
<BR>Your tank-circuit &nbsp;needs less L &nbsp;and it becomes very likely that 
shorted 
<BR>turns 
<BR>act as tesla coils causing arcs through the bandswitch if distances between
<BR>contacts are not wide enough.
<BR>
<BR>So far I have no experience with the 4-1000 which is comparable 
<BR>to the QB5/1750 which I use in a couple of homebrew amps.
<BR>But I have used both, QB4/1100 and 4-400, in my modified L-4B.
<BR>There was no difference in gain with both types ( 12-13db ) at 4KV, so 
<BR>probably the 4-1000 being in the same family, will amplify likewise with
<BR>anode voltages between 4.5 and 5KV. 
<BR>
<BR>Measurement equipment here are Bird and R&amp;S wattmeters + scope .
<BR>
<BR>73, Peter
<BR>
<BR>
<BR>
<BR>
<BR>
<BR></FONT></HTML>

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