Re: Will Radio Engineering be QM's worst nightmare?

"Ron Baker, Pluralitas!" <stoshu@xxxxxxxxxxxxxxxx> wrote in
news:VI9te.21574$h86.18678@xxxxxxxxxxxxxxxxxxxx:

>
> "bz" <bz+sp@xxxxxxxxxxxxxxxxxxxx> wrote in message
> news:Xns9679C50C92EBFWQAHBGMXSZHVspammote@xxxxxxxxxxxxxxxxx
>> curiousjohn4@xxxxxxxxx wrote in
>> news:1119117816.261866.169700@xxxxxxxxxxxxxxxxxxxxxxxxxxxx:
>>
>>> bz wrote:
>>>> Do the math. See what kind of voltage gets produced by 150 watts
>>>> applied to an infinite resistance.
>>>
>>> Yes, but you're thinking of something like a large inductor with
>>> current going through it and then stopping the current.
>>
>> I am thinking of an amplifier that is turned on with no load. Not
suddenly
>> removing the load while it is running. In either case it can blow the
>> output transistors.
>
> I hear you on this matter.
> If an RF source doesn't have a matched load the
> power is reflected back to the source.

It happens at audio frequencies also. In the early 70's I had a consumer
electronics repair shop in Wichita Falls, Texas. People were always
bringing in their expensive Hi-Fi Stereo Amps with blown output
transistors. The designers had an A,B,Headphones switch that switched the
output between output terminals on the back and the headphone jack.
Switching at high volume, or having switch in wrong position and turning on
the amp would fry the transistors. If the designers had hung a 32 ohm or so
resistor across the output, it would have saved a lot of grief.

> The source could be designed to withstand the
> full power being reflected back but that is not
> typically done in the case of power amplifiers.
> It would be waste of resources to design
> for that pathological case.

Failsafe design is often no more difficult than faulty design.






--
bz

please pardon my infinite ignorance, the set-of-things-I-do-not-know is an
infinite set.

bz+sp@xxxxxxxxxxxxxxxxxxxx remove ch100-5 to avoid spam trap
.

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