[Elecraft] ESD precautions?

Stuart Rohre rohre at arlut.utexas.edu
Tue May 25 14:17:38 EDT 2004


Actually, we find that long grounds often enhance pickup of 60 Hz induced
voltage and harmonics from the usual imbalance in residential power or
industrial power lines.  That is a whole different subject of power line
RFI/EMC with which I worked professionally for over 40 years.

The main principle of static protection is to get everything to the same
equipotential plane, (same voltage) such that an arc cannot happen from a
place of accumulated charge to a static electricity sensitive junction or
other component.  This is achieved by use of anti static, (dissipative)
materials; and bonding of work surfaces, the operator, and tools and
components by the common conductive material of the work pad, wrist strap,
etc.  When such bonding is effective; any charge dissipates thru the
associated series resistance and spreads to all surfaces equally rather than
building up as on a charged plastic tool handle or other insulator.

There is no magic ground rod that will drain everything away without doing
all the steps that make an effective anti static environment.   The whole
work environment must include anti static tools, connections for workers,
work table surfaces like the pads, and in extreme cases anti static  ionizer
equipment to neutralize charge buildup.   Sprays are used to make surfaces
dissipate charge buildup.   Humidity and temperature are controlled or taken
account of, to avoid dry, cold, static favorable conditions.  In outdoors
areas, we have found dry winds increase static buildup, and can be as bad as
the worst cold Winter day, even in Summer.

Hams operating portable from windy mountain tops, or desert areas should
provide static discharge devices for balanced antennas to avoid rig damage
to front ends.   Even when a storm is not approaching, rigs should be
disconnected from antennas to avoid static surprises of wind induced static
charge on antenna wires.  Those operating loops, long wires, vee beams, and
such are most vulnerable, but even a half wave 40m dipole up as an inverted
Vee 40 feet at apex; was observed to have 90 volt build up with approaching
thunderstorms.  (A neon lamp and resistor was placed across the dipole
feeder to dissipate charge and was flashing with the storm 5 miles away).

-Stuart
K5KVH




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