Peter Chadwick wrote:
>Rich said:
>
>>IMO, the electric-mains is a greater danger. With HV, the careless
>idiot
>>often gets blown clear. With 120v/240v, he typically can not let go.
>>Next stop, "Silent Keys" in *QST*.
>
>It is claimed in many places that the most dangerous voltages are
>between 400 and 1600 DC, as that usually leads to ventricular
>fibrillation. Some people claimed that sweep tube linears were safer
>because the voltages were lower - another myth!
>
>But having had a number of bad shocks in the past, I suggest being VERY
>careful. It's surprisng, as Rich says, how many people get blown clear -
>it happens on the 25KV overhead electric lines used here for the railway
>- about 10% get blown clear, while very few survive the 750volt DC used
>on the third rail systems here. That's not enough to rely on it, though.
"Blown clear" is not quite what happens. With the kinds of voltages used
in house wiring and amateur radio, there's not enough electrical energy
available to propel a human body. The shock causes a violent muscle
contraction and we literally throw ourselves clear - much harder than we
could leap voluntarily.
What happens depends very much on the method of contact, the posture at
the time, and which muscles get stimulated. On a damp day in a grage
with a bare concrete floor, I once saw somebody tinkering with a live
240V socket and go flying across the room - but that's because he was
squatting down, and the shock contracted all his major leg muscles. What
happened when he hit the opposite wall was much worse than the electric
shock.
73 from Ian G3SEK Editor, 'The VHF/UHF DX Book'
'In Practice' columnist for RadCom (RSGB)
http://www.ifwtech.demon.co.uk/g3sek
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