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[AMPS] L-Net calculations: Am I doing something wrong?

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Subject: [AMPS] L-Net calculations: Am I doing something wrong?
From: (
Date: Thu, 18 Feb 1999 01:46:09 -0500

On Wed, 17 Feb 99 16:56:09 -0600 Jon Ogden <> writes:
>>>Why does my power output top out at 800 Watts?  Once I get over 60 
>watts of 
>>>drive, I get no more power out no matter what I do.  
>>?  Sounds like a tuned input problem.  What is C1?
>Interesting.  I forget what C1 is.  I would have to check.  I have 
>thought it might be a problem given the fact I am using slug tuned 
>coils.  Perhaps the slugs start to saturate.  The 10m input SWR isn't 
>perfect right now, but is under 2:1.  I need to adjust the slug a bit. 
> But what does flat topping have to do with the value of C1.

More to the point, exactly what is the 10M input network, as I asked 2
weeks ago ?
Have you ever measured any of the LC values?
What is the material in the slug tuned coil?
What is the wire size and coil diameter?
What is the output on 12M, 15M, and descending bands?
What is the exact VSWR on all those bands?

Its my turn for questions. How about only answers for once...

>>>The current will 
>>>change depending on what amount of drive you have applied to the 
>amp.  So 
>>>I what I think you are saying is that you would need to drive the 
>amp so 
>>>that the plate current is at 0.8 A.  But then if you decrease the 
>>>you would change the impedance and hence the match.  Correct?
>>?  yes x 3.  The guy who wants to take it easy on his linear amp. and 
>>tunes up with reduced drive, gets a mistune every time.  .  . 
>Well, correct.  However, I was taught to tune it up initially with low 
>power and then gradually crank up the power, tune it, crank the power 
>more, tune it, etc. until you get to full desired output power and 
>then do a final tune job on it.

That is one correct way to do it.  And also probably the safest when
debugging an amp or firing up a new toy out of the box. 
Balls to the Wall with full drive is for the less timid as long as you
know which way to turn the load cap and have the third hand on the AC
breaker. One has not passed the final test until one has witnessed the
holy light from a white 4x1 plate.

73   Carl  KM1H

>Jon Ogden
>"A life lived in fear is a life half lived."
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