[Elecraft] Automatic lightning protection for radios, .... an off the wall idea

[Bob McGraw]

Just remember that ALL lightning protection must be accomplished outside 
of the house or structure.  Do not think for one minute that one can 
provide lightning protection inside the equipment or structure.

Any and all driven ground rods and systems MUST be bonded back to the AC 
Mains ground.   This is per NEC.   Many hams violate this rule and 
actually create a condition where equipment WILL BE damaged by a near-by 
lightning strike.  This occurs by not bonding the station ground to the 
AC Mains ground outside of the house. Hence by this not being done, 
there are 2 or more ground points with resistance between the points and 
the path of current is through ones equipment regardless, if antennas 
are grounded, disconnected, and the equipment is turned off.

73

Bob, K4TAX


Message: 4
Date: Sun, 17 Jan 2021 22:33:47 -0500
From: Bill Frantz<frantz at pwpconsult.com>
To: Elecraft Reflector<elecraft at mailman.qth.net>
Subject: [Elecraft] Automatic lightning protection for radios,	an off
	the wall idea
Message-ID:
	<r480Ps-10146i-E45F0FA84C894CF99A526B5D4BE9EEE6 at Williams-MacBook-Pro.local>
	
Content-Type: text/plain; charset=UTF-8; format=flowed

I've been thinking about some kind of automatic lightning
protection for radios, specifically ones like the K3 and K4. The
idea is that when you turn the radio off, all the things that
are subject to damage are protected by disconnecting them from
the external world and shorting their inputs to ground.

This approach probably wouldn't protect against a direct hit to
one of the wires coming into the radio, which are most likely on
the antenna input and the power from a solar system. But I
understand that the most significant part of the problem is
voltage spikes introduced when the external wires act as
antennas and pick up nearby lightning strikes.

I'm not a hardware engineer, so I'm going to assume that relays
are used in this device. Some of the things I see this device
doing are:

USB connection: Elecraft tells us that blown USB chips are one
of the more common forms of lightning damage in the K3. There
are 4 wires in the USB interface, two of which carry power from
the external world. The relay(s) would float the USB wires and
ground the connections to the internal USB chip. Since power
from the external world is present when the radio is off, we
can't ground the power leads, although we can ground the power
input to the radio's USB chip.

Note that currently a computer attached to the K3 can see its
USB chip, even when the radio is turned off. This change would
mean that the computer would no longer see the radio over USB,
which might have annoying software effects.

A similar thing could happen to the antenna inputs.

Key/Paddle, microphone, headphones, RS232, etc. would be treated
the same way.

The AUXbus would be treated similarly, but anything that can be
turned on via the AUXbus would need special handling.

The 12V power input is needed to turn the radio on with the
power button. I don't know how often radios are damaged through
their 12V power input. This input may not need protection.
Otherwise, the relay that protects power and the switch to the
radio could be the only things powered when the radio is off. If
it can't be protected, it could be made easily field replaceable.

It would be neat if there's enough room inside a K4 to put this
kind of protection "under the covers".

73 Bill AE6JV


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