[Elecraft] Shack equipment noise

[Keith Heimbold]

I will confer with my electrician as I just had major electrical upgrade completed in January.  I was planning to get a dedicated 240V line installed anyway.

Thanks,

Keith
AG6AZ

Sent from my iPhone please excuse typos

On Dec 12, 2011, at 9:17 AM, "Jim Brown" <jim at audiosystemsgroup.com> wrote:

> On 12/12/2011 9:04 AM, "Carl, WCØV" wrote:
>> What isn't mentioned is the fact that MOVs are rated by the TOTAL energy
>> in Joules that they will absorb in their lifetime before they fail. The
>> energy absorbed from spikes is cumulative and when the rating is
>> exceeded, boom.
>> They are also responsible for nasty noise generated by the crowbar
>> action on the spikes in making them square waves - the sum of all
>> possible harmonics. I
>>   used to have to deal with these things when customers would use them
>> in front of servoamplifiers. The noise from the square waves drove us
>> crazy until we found the MOVs and removed them.
> 
> YES!  We learned about this in the pro audio world as well, and did the 
> same thing to search out and destroy them. And yes, they are insidious, 
> in everything from copy machines to printers and even power supplies. I 
> found some in an Astron power supply when they failed.
> 
> The WORST thing about MOV-based protectors is that they CAUSE 
> destructive failures of equipment that is interconnected by low voltage 
> wiring when that equipment is plugged into different power outlets, even 
> when all of the outlets are "protected."  That's because they dump the 
> surge into the green wire that serves each outlet, the length, and thus 
> the voltage drop due to the surge to each outlet is different, and the 
> DIFFERENCE blows up the equipment.  That's why MOVs are ONLY a good 
> thing at the service entrance.
> 
> 73, Jim Brown K9YC
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