On 7/27/2012 10:51 AM, Michael Tope wrote:
> On 7/27/2012 7:11 AM, Jim Hargrave wrote:
>> Duh...
>> Why not just use the RF PWR adjustment on the front of the transceiver and
>> save all that costs and wasted heat dissipated by the attenuator.
>>
>> "Discipline" is the keyword. With proper drive power management, most
>> linears will operate trouble free for decades.
>>
>> I have a Clipperton-L (1980) with the original tubes. I also have a
>> homebrewed 4-400(2) that I built in 1979. I did not even bother to include
>> an ALC circuit. Both have been trouble free.
>>
>> 73s de Jim
>> W5IFP
>>
>>
>
> Jim,
>
> The issue isn't so much lack of discipline as it is the power overshoot
> of the internal ALC circuits found in many modern solid-state
> transceivers. Yes, a disciplined operator can dial back the RF drive on
> his rig to the proper, but if the ALC loop in that transceiver
> overshoots on the leading of the RF envelope, ceramic tubes with
> sensitive grid structures or the solid state devices, both of which are
> found in many modern amplifiers, can be damaged.
Ceramic tubes the size of those old 4-1000As don't have a bit of trouble
either.
73
Roger (K8RI)
That's the one nice
> thing about the older glass envelope tubes like the ones in the
> amplifiers you describe. They tend to be more forgiving with respect to
> short-term over-drive. Still, even if the tubes can take it, this sort
> of power overshoot can cause unwanted distortion (key clicks, IMD, etc).
>
> 73, Mike W4EF....................
>
>
>
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