[Elecraft] Living with EMP'S

[Joe Subich, W4TV]

On 5/25/2012 1:40 AM, Jim Brown wrote:
 > All these lightning things on serial and USB ports sound like Pin One
 > problems to me.  They also sound like equipment powered from different
 > AC outlets, perhaps even with MOV surge suppressors.

They generally are "different ground" issues.  The radio is typically
connected to the antenna system ground (even when antennas are pulled)
and the computer is connected to the power system "safety ground".  In
addition, many computers keep the USB power alive during "sleep" and
often even when turned "off".

A nearby lightning strike can result is differences of several volts
between the chassis (antenna/RF ground) and the power "safety" ground
which shows up across the USB power (increases or decreases it).  USB
power greater than 7 or 8 volts or negative can and will destroy the
USB UART and other USB powered components in most equipment.  Better
manufacturers are now adding surge suppressors to the USB power and
data lines in their devices but they are not 100% protection.

Proper grounding and bonding are essential.

73,

    ... Joe, W4TV


On 5/25/2012 1:40 AM, Jim Brown wrote:
> On 5/24/2012 10:05 PM, robfrick7 at aol.com wrote:
>> I have a flex 1500 that took an EMP hit on the USB port last year.
>
> All these lightning things on serial and USB ports sound like Pin One
> problems to me.  They also sound like equipment powered from different
> AC outlets, perhaps even with MOV surge suppressors.  Both are well
> known causes of lightning damage, as well as problems with hum and buzz.
>
> 73, Jim K9YC
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:Elecraft at mailman.qth.net
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
>