[Amps] AL-80B questions

[rlm]

>rlm wrote:
>>
>>Amplifiers that happen to have tubes with lower than average VHF 
>>amplification tend to be stable.
>
>High-gain amplifiers for the VHF bands are perfectly stable too, if they 
>use tubes with short, well-grounded grid (or cathode) connections.
>
**  HF amplifiers invariably have two resonant circuits connected to the 
anode.  VHF amplifiers have one.

>The key feature is the total length and inductance of that grounded 
>connection. The length outside the tube is controlled by the layout. The 
>length inside the tube is controlled by the choice of tube. If you also 
>prevent accidental feedback paths, you'll have a stable amplifier.
>
**  So the g-g internal feedback-C from the anode to the cathode (or grid 
in grounded-screen tetrodes) is nothing that a true amplifier expert 
should be concerned with ?

>If you use the correct grounding techniques in a VHF amplifier, it will 
>be stable with both the input and output disconnected.
>
**  correct gounding has zero inductance ?

>The gain of tubes does not increase dramatically at lower frequencies 
>like it does with transistors, so if you use "VHF" grounding techniques 
>in an HF amplifier, you'll have a very stable amplifier indeed.
>
**  VHF grounding also has no L ?

cheerz, Ian 

-  R. L. Measures, a.k.a. Rich..., 805.386.3734, AG6K, 
www.vcnet.com/measures.  
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