Electronics > RF, Microwave, Ham Radio

antenna static protection

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m3vuv:
Hi all,ive been thinking about static protection for my triband collinear up at 45ft,i see lightening protectors are expensive,i have thought about using a spark plug in paralell with a 10 meg ohm resistor from the coax center conductor to ground,is that a good idea in a waterproof box?

cdev:
Its not good protection for RF. You need something better.

You also need a good ground.

floobydust:
Normally I would use a Polyphaser it's just a 300V/20kA gas-discharge tube packaged in a housing but they seem overly expensive at USD $85. On Aliexpress they are USD $14 but not sure what's inside for quality, still cheap if you have to use the housing and put in a higher quality GDT. Not sure if waterproof but we used flex tape to seal it up the RF connectors too.

Automotive sparkplugs have a carbon resistor of a few k ohms inside the porcelain, which would make them poor at clamping. You'd have to use a special sparkplug, the ones for ignitors on oil burners have no resistor. Even then, using an air gap can suffer from ozone buildup which increases the breakdown voltage.
Sparkplug threads are oddball Metric i.e M10x1.25 Champion France set that in the early 1900's, so finding a nut or tap is extra expense, then water-proofing it.

I don't know what Mr. Carlson did for protection after his antenna stray charge build-up (in winter snow storm), if you remember the video. He's put up another antenna since.

m3vuv:
its static im concerned about not the rf,as i unerstand the base of the antenna should be a current node not votlage if the swr is ok ish?,i only use 10w tx so cant see the spark plug arcing out on tx,just thought better than nothing on the cheap lol ?.

m3vuv:
most resistor plugs have "R" in the part number,ie champion n-9y=non resistor rn9y= resistor type,fitting could be done with a hose clamp and the normal nipple on top for the live wire,my idea the resistors bleed off static and any high voltage transiants caused by a local strike gets taken care of by the plug spark gap.

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