Skip,
Yes, there are various causes of static on the feedline, but static is
static. It is a voltage charge on the feedline and it can damage equipment.
The source may be wind blowing on your antenna, rain or snow that
carries charged particles, or nearby lightning. No matter what the
cause, it can produce a significant voltage across your feedline. It
does not take a direct lightning hit to produce damaging voltages on
your antenna feedline. A direct hit can cause damage to house and home
and any equipment in that home, but there are other times when the
accumulated static voltage on any feedline can cause damage to your ham
equipment.
I recall an event many years ago when I got that lesson. I had several
antennas in the basement shack unterminated and just waiting to be
connected. The wind was blowing and I thought nothing of it until I
picked up an open feedline and placed it near my Heathkit HW101
intending to connect it - sparks flew as the coax got close to the
chassis! That was a warning to me - disconnect and ground all my
feedlines when not in use. If not grounded, at least a bleed resistor
across the feedlines to discharge any built up static.
73,
Don W3FPR
On 10/31/2018 6:42 PM, Fred Jensen wrote:
Hmmm ... There seem to be different flavors of static. My reference was
to what is often called "precipitation static" [rain, snow, maybe hail]
and which can sometimes also be caused by wind blowing sand/dust past
the antenna. It sounds like bacon frying in the receiver. Each drop or
snowflake acquires a minuscule charge falling or blowing which
discharges into the antenna on contact. The typical semiconductor
devices in radio front ends these days exhibit a nearly infinite
impedance to "ground" and a tiny capacitance. The constant little
pulses from the static charge that capacitance with essentially no
discharge path. That's what fried the 1st 760 II and then, predictably,
the second one.
There is also the combined "static" caused by distant thunderstorms.
INT QRN: "Are you troubled by static"
QRN: "I am troubled by static"
which is different than "static" caused by corona or leakage on a high
voltage power transmission line.
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