R; Measures wrote:
>
> On Mar 10, 2006, at 2:12 AM, Steve Thompson wrote:
>
>>
>>
>> Saandy wrote:
>>
>>> ....yeah! Now, you have arching, like you wanted (HI).
>>>
>>> It probably needs more inductance in the suppressor. According to W6SAI
>>> (blessed his memory), the 4-1000 needs 4 turns, 16 gage, ½ inch
>>> diameter
>>> suppressor coil with 2 47 ohms 2Watt resistors in parallel.
>>
>> I'm intruiged by this, and I'm wondering if I'm misunderstanding
>> something.
>>
>> As I understand it, the tube doesn't oscillate in isolation - it's a
>> combination of several factors, including the impedance presented to the
>> plate. At some frequency there's an impedance in the wiring from the
>> plate to the tune-C and then to ground that allows oscillation. Knowing
>> the frequency and impedance allows you to design a suppressor to prevent
>> oscillation, but the frequency and impedance can vary a lot with wire
>> lengths, component choices and layout - in which case, how can there be
>> a specific design of suppressor for a particular tube?
>
>
> The optimal suppressor design is that which almost melts down the
> suppressor resistor at 29MHz,
I can see that gives you a 'standard' design for any given plate load
impedance - not necessarily for a specific tube.
Depending on the frequency and excess gain to be killed, it might not be
necessary to cook the suppressor at 29MHz to kill the oscillation.
Adding L increases dissipation at 29MHz,
> decreases the parallel-equivalent resistance seen by the anode at its
..increases.. I think.
> VHF self resonance, and that decreases VHF gain at that frequency --
> hopefully making the amplifier less squirrelly.
Steve
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