[Elecraft] ESD Risk vs Relative Humidity

[Alan Slusher]

I recall as a kid reading stories (in the science books) of static
electricity with cats' tails, and of combs picking up bits of paper.  Could
never duplicate those occurrences, and hadn't the faintest (demonstrated)
idea of what people were talking about.  Just accepted what I read as fact
somewhere in the world.  This was growing up in Belize (then British
Honduras), south of what is now Cancun on the Yucatan Peninsula.
Temperatures generally in the thirties (Celsius), and relative humidity at
least 80%.

Built Heathkits, operated many radios, went to college in Jamaica, travelled
all over the place (always going to warm places, or to cold places at warm
times of the year), never an ESD event (still could not get the comb to pick
up paper).

Then, in the late 1990s (all of 50+ years of age), I spent three years in
Rockville, MD.  Autumn and winter the first year.  Fully carpeted house.
Every doorknob was a problem.  The little screw holding the plate over the
120v wall power socket was a problem.  The car door handle was a problem.
Tingles, and lots of little sparks.

And then it hit me:  Back home in the tropics the humidity is generally so
high that electrical charges leak off into the relatively damp air before
they have time to accumulate to any appreciable extent.

Now living in Barbados: air-conditioned bedroom with a rug on the floor.
Cool the room way down, and relative humidity declines.  Walk on the rug,
touch an internal doorknob: you could see the spark jump!

The hamshack is air-cooled.  A big electric fan.  Relatively high humidity.
No ESD issues.

Cheers, and Season's Greetings.

Alan  8P9BM

-----Original Message-----
From: elecraft-bounces at mailman.qth.net
[mailto:elecraft-bounces at mailman.qth.net] On Behalf Of Joe Wilkowski
Sent: Wednesday, December 20, 2006 17:32
To: Mike Short
Cc: Elecraft at mailman.qth.net
Subject: Re: [Elecraft] ESD Risk vs Relative Humidity

My 2c worth.  I have posted on this reflector before my experiences with ESD

and my K2 as I was building it.  First, understand that  I live in the 
mountains of Colorado at about 8200' ASL.  It is extremely dry here all year

round and especially in the winter months when the RH rarely gets above 60 %

To make matters worse, we are remote enough so that our home is 100% 
electric which is expensive so we supplement the heat with two wood burning 
stoves up and down.  There isn't much more we can do to put humidity in our 
air than to keep fancy water pots filled on top of each stove.

I have read many comments here before on the ability of the K2 to withstand 
ESD discharges but I can attest to having to do a complete reset of the K2 
and reload all parameters on two occasions this season.  Both of these 
instances occurred during the later stages of construction and alignment. 
These ESD related issues occurred while I was wearing a ESD wrist strap tied

to the ground/neutral buss of the house supply.  ESD is real and the K2 is 
definitely NOT immune.  Since completion, and while the radio was fully 
buttoned up with all panels, the K2 has suffered ESD shutdowns of audio and 
other functions but was quickly remedied by cycling the power.  It seems at 
times that  I cannot move around in my chair without zapping the little rig.

So my recommendation is to utilize ESD protection at all times when 
constructing or working on the interior of the rig.  Again, your mileage may

vary but these are my experiences.

/joe k8fc