Having seen and been given a few nasty jolts in my formative years - Im now very cautious working on the LF and MF arrays - especially when transmitting, but my thoughts of static and painful discharges normally relate to larger (sic) vertrical arrays and similar, I didnt think I would be thrown across the field and have that nasty metallic taste in my mouth again.
Heres the scenerio - (Its got a bit of MF in it honest) : - Location about 5000 ft asl Central America - Date - About a month ago.
Ive up a commercial wideband dipole at 40 foot and the RG213 is due replacement - I disconnect from the radio end - so the coax in the shack exactly 80m away is left floating..... I move to the antennae site I dig out the coax from the ground under the antennae which is buried just for a couple of feet (just vegetation over growth) and pull down the coax and antennae, (which by design is DC grounded via a transformer - I wont call it a Balun/un) I strip off the insulation (self amalgamating and pvc tape overlay) -
I disconnect the antennae (which is laying mostly on the ground) from the coax plug holding the outer of the pl259 - I drop the cable to ground (its dry) and sort out the antennae for 5 mins.
I then pick up the cable and my hand touches between the inner pin of the PL259 and the outer - there is a massive White flash and bang, I see Green, Im thrown backwards and look like Ive had too much Merlot (again) - Sheri comes bounding across the field in here Green Wellies (Hunters of course) and pulls me up -- " What the......etc?" My first shock for over 30 years in radio.
But what could have caused this - it wasnt stormy - its wasnt that dry either really and Im in the middle of a field with only the far off steaming and ash visible from the Turrialba volcano.
I check the far end and short it to ground using insulated tools - nothing - I check insulation resistance etc... so Im guessing the inner and its dielectric and the capacitive affects of the cable produced a viable storage cap. Im guess I got a Kv or two, but moreover it had a punch so quite a bit of current flowed too.
Just a warning about old dogs learning the hard way - never presume an open circuit long length of piece of coax - even if its laying on the ground may not have a residual static charge build up between the outer and core. Its a new one on me.
In the Antarctic and Arctic the charges on the outers of coaxs can be quite amusing to watch - I had two RG58s spaced about 6 inches apart hanging/dangling with about a 1m length - as the charge built up on the cables from the passing dry snow grains outside (blowing 50 and -50 to boot) - the cables started to oscillate and be attracted to each other gradually gaining momentum till there was a big flash and band and the coaxs went back to their resting position.
I did say there would be something relevant to LF/MF in this - one of the coaxs went to a NDB!
Last story - that NDB had an intermittent open circuit/high SWR trip and I couldnt figure it out till I went outside and saw an Arctic fox jump from a nearby piece of blue ice and snap with her jaws onto the coax going up to the antennae and then her whole body idly swing to and fro for a few secs before letting go and then jumping back onto the ice block and doing it again and again. Very amusing and no wonder the coax has given a short where the teeth had push the outer and inner together. New coax required and raised the coax off the ice a bit more...
Laurence By3a kl1X
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