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
> _______________________________________________
> Amps mailing list
> Amps@contesting.com
> http://lists.contesting.com/mailman/listinfo/amps
>
R L MEASURES, AG6K. 805-386-3734
r@somis.org
_______________________________________________
Amps mailing list
Amps@contesting.com
http://lists.contesting.com/mailman/listinfo/amps
|