[Amps] Ameritron Amps

[R L Measures]

On Aug 1, 2006, at 8:19 AM, Steve Thompson wrote:

>
>
> R L Measures wrote:
>>
>> On Jul 31, 2006, at 10:38 AM, Steve Thompson wrote:
>>
>>>
>>>
>>> R L Measures wrote:
>>>
>>>>>
>>>>> I can see an oscillation causing very high dissipation,
>>>>
>>>>
>>>>
>>>> Push-pull parasitics, yes, push-push parasitics no.  To  
>>>> explain:    With
>>>> a push-pull parasite, the VHF energy from one tube alternately    
>>>> pushes
>>>> energy into the other tube,and vice-versa, so both tubes have  high
>>>> dissipation until the operator stops transmitting.  However,  since
>>>> there is a load on each half-cycle, there is no wild and crazy    
>>>> arcing,
>>>> and grid-I is not excessive. If you want to see a push-pull    
>>>> parasitic,
>>>> short out both parasitic suppressors in a SB-220,  transmit,  
>>>> and  with a
>>>> litle bit of luck you will see both anodes turn  bright red,  The
>>>> frequency is c. 50MHz.  .
>>>>  However, Push-push parasitics tend to run amuck because they  
>>>> are   not
>>>> loaded.
>>
>>
>>> Sounds very complicated.
>>
>>
>> Push-push is like a pogo-stick.  Push-pull is like a see-saw.  It's
>> elementary, Steve. cheerz

> The topology is straightforward enough, not so the idea that one
> topology won't give high dissipation, the other won't give high  
> voltage.

With push-pull VHF oscillation in a paralleled 2-tube HF/MF  
amplifier, even though VHF energy can not escape through the low-pass  
tank, the tubes conduct alternately, so the energy from one tube  
alternately heats the other tube during each half cycle. However,  
with push-push VHF oscillation, both tubes conduct at the same time,  
the low-pass tank blocks the energy's escape, and there can be  
fireworks.
>
> Steve
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R L MEASURES, AG6K. 805-386-3734
r at somis.org