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

[km1h@juno.com]

On Wed, 17 Feb 1999 14:43:06 -0800 Rich Measures <measures@vc.net>
writes:
>
>>Some guys use a 1.8 number as the multiplication factor for I-anode.  
>
>
>€  With an 8877, or a similar triode, so would I.


Hoff recommends 1.57 for Class B and 1.3 for A . You can pick a number in
between for AB2 and be close enough to end the discussion.

That gives you close enough to 5K for government work. 


>
>
>>No matter, it still is much less than the 4600 Ohms I was using.
>>
>>Using your formula, the 4600 Ohms assumes an I-anode of c.500 mA.


A good 4x1 will key down 700-800ma. Since key down is your measuring
point why go for some other value? It will still be darn close to SSB
peaks.
I suggest you reread " Care and Feeding" and some of Orrs articles and
maybe you will not have to ask questions almost daily for a year ( or is
it 2 years already) plus just to get a basic amp going.


>>
>>OK, so answer this then: Why am I having problems matching on 10m?  
>
>€  I would have to measure some things to figure it out.  


Basic tools come in handy.


>
>
>>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?


I asked that question a few weeks ago and got no answer, just more
questions.


>
>>In looking at everything I was assuming it was becasue Q was too 
>high.

Altho that Q is very high and can cause problems, where is it written
that it cannot be used?  At least for a starting point?
Since I and others have mentioned numerous times that the B&W 850 10M
coil is almost always modified for a single 4x1 why do you persist in an
endless barrage of questions?  
Why not just spend a week doing some real engineering work and report
that you finally reached the same output efficiency level as probably
several hundred others have done over the years.

I'm not looking for an argument Jon or comments from Zitland either. But
dont you just think this project is getting a little bit tiresome to more
than just myself? Two years !!

On a more positive note, how about scanning in pictures of this beast
along with a schematic and at least the important component values?  I
have lost track of what you have any longer, its been that long.  Perhaps
a picture is worth a few megabytes of more questions and someone may be
able to spot a problem straight away.



>>
>>What light can you shed on this?
>>
>>Also, how do you determine your peak anode current.  
>
>€  look at the constant-current characteristic curves.  For good 
>linearity, pick the highest peak-current curve that has a defined knee 
>at 
>the anode/plate potential equal to the screen-supply voltage.  For the 
>
>8166/4-1000A, the highest  such curve is 2.6 peak-amps.  Divide 
>peak-current by 3 to obtain avg. current.  This is how I arrived at 
>the 
>c. 0.8A figure.  


Right on the money Rich,  always been my experience in real life 4x1
versions.

>
>>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 
>drive, 
>>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.  .



AMEN !  Along with a 30KHz wide signal when he cranks the drive back up
without retuning. Come to think of it that must be the popular method on
the ham bands.

73  Carl  KM1H



  . 
>
>-  cheers, Jon
>
>
>Rich...
>
>R. L. Measures, 805-386-3734, AG6K, www.vcnet.com/measures  
>
>
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>

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