antenna static protection

[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.

[floobydust]

What ends up happening is the arcing occurs across the 10MEG resistor. Is it rated for a few kV lol. The spark plug could work if it's dry and has low impedance grounding, and I'm not sure how much of a stub you'd get with the run to the normal nipple as you call it. Spark plug wire is typically also resistive, so you'd have to use different cable to the nipple while keeping it waterproof.

[cdev]

Snow can do that!  Wow!!!

Scary!

These parts are pricey. Are they the best buy in HV RF protection, even? It's difficult to see where the cost comes from. ANYbody know whats behind these huge prices? I almost can't believe they are for real!

[floobydust]

Winter is a bit weird because there is no lightning or thunderstorms so I'm not sure what prevents clouds from charging up seasonally. I thought the E-field might have been very high and snow being triboelectric might have been part of it. Wire antennas are just asking for it.
Here I thought a 20kA GDT would be OK for a lightning strike but apparently no. Pic is from WA5MLF Lightning damage to antenna the GDT blew up and arc bypassed the 1MEG per Murphy's Law.
The Polyphasers are overpriced, although I did specify using them and had zero problems. DD1US Teardown of one did not show much inside.

[cdev]

We have a 'real' winter here in NJ and a real summer too with lots of lightning storms and the like. Not the very worst of lightning storms, though.. But it still gets real on us now. Not like the SF Bay Area where there are almost no lightning storms. anymore. . I'd like to have real lightning protectiuon.

But $1800 for a lightning arrester is too much!  So is $150

[m3vuv]

as i stated spark plugs without the "R" prefix dont have resistors in the center electrode,too my mind using a resistor in paralell with a spark plug has to be better than nothing,rather static bleeds off that way as oposed to the radio front end,im not talking of a direct hit but static from rain and nearby storms etc.

[floobydust]

What breakdown voltage do you think you will get? Air breakdown is roughly 3kV/mm (1atm, dry air) between two spheres, and 1.5kV/mm for needle electrodes with no ion build up.
A gap of say 0.5mm/0.020" might be around 1-1.5kV which does protect your wiring and connectors - but not the radio. A fast rising edge (lightning impulse) can cause up to 10x increase in the breakdown, compared to DC sparkover voltage.
GDT's have flatter electrodes and pressurized gas (i.e. Ne) for lower, more consistent firing voltage. You could use a neon lamp for static charges but at high energy they just explode.
I think the spark plug would be tough but a bit HV to protect the radio.

[antenna]

What about an LCL pi network?  The input and output are at DC ground due to the coil.  Design it for the lowest frequency as its effects get less with increase in frequency.  If its a 6m/2m/70cm tribander, try 330nH-82pF-330nH.  That coil would be about 10 turns with a 7mm diameter wire and overall length of 10mm.

edit: was going to mention surface mount capacitors because of the self-resonance of leaded parts, but now I wonder if that coil is too big at 70cm and if it's parasitic capacitance could make it useless at 70cm.... i might get bored and try

[Ringmodulator]

Static build up on antenna systems and high voltage from lightening are two different cases.

Satic charge can be especially harmful if when coax cable is not connected to the transceiver, because the feedline acts like a capacitor and can store quite some energy.
If it is then connected to the trx, the hv energy discharges into the trx.

A bleed off hv resistor to ground will keep the antenna and feedline discharged. It also lowers noise from static in the rx.

But this will not do much in case of nearby lightening strikes.

Normal lightening protectors dont help against statc build up.

Chris

[cdev]

Polyphasor patented?  If so, what's the number?

[coppercone2]

can you make some kind of power generator for this in the correct climate with lots of triboelectric activity? Might look like an antenna but not really be a good antenna. Like if there is a switch that discharges the energy into a circuit once its charged.

[floobydust]

Polyphasor patented?  If so, what's the number?

Transtector and Polyphasor are brands of INFINITe Electronics as well as Pasternak, L-Com many others etc.
Lightning protection - there are 100's of patents out there. Look at Transtector/Polyphasor patents.

They (Transtector) are always adding inductance in series with the protective element(s), and using a ring-array of TVS diodes or gas-tubes or MOV's, tuned to MHz.
"The RF impedance of the spiral inductor is at least 10 times the operating impedance, i.e., 500 ohms for a 50 ohms system."
So they lessen loading in the GHz but maybe add a delay to the already slow GDT. I guess it's OK: "Lightning Surges generally include D.C. electrical energy and AC electrical energy up to approximately 1MHz in frequency."
They seem to be saying the RF path must be GHz fast, but the lightning path can be relatively slow in comparison. pic from US8456791.

As far as static charge buildup, much less energy than lightning but the slow voltage build up.

[cdev]

I think this is important and many people dont realize it. That video of the snow and high voltage just opened my eyes. I wish we could use that for energy!

Static build up on antenna systems and high voltage from lightening are two different cases.

Satic charge can be especially harmful if when coax cable is not connected to the transceiver, because the feedline acts like a capacitor and can store quite some energy.
If it is then connected to the trx, the hv energy discharges into the trx.

A bleed off hv resistor to ground will keep the antenna and feedline discharged. It also lowers noise from static in the rx.

But this will not do much in case of nearby lightening strikes.

Normal lightening protectors don't help against static build up.

Chris

[coppercone2]

can you just put a bleed resistor with a choke on it? All but the highest frequencies should be fine. And the high frequency one have radoms so they should not get charged up. Piece of ESD mat tied/ziptied to antenna between the dipole? Maybe you can cast some kind of barely conductive plastic shorting jumpers.

What i don't get is if there is a 50 ohm resistor to ground at the input, how is charge building up in the first place? Should it not be bled all the time? I guess the problem is capacitive coupling. Surely this is not a problem for DC coupled systems..? The attenuator should do it.

If you have teflon insulation water proof cable that is AC coupled then I can see this being a problem. I guess people are often protected by old waterlogged cable etc. That's probobly why we don't hear about this problem very often.

[A.Z.]

when it comes to static (and lightning) protection, the best approach imHo is a "layered" one, that is, don't rely on a single device, but use multiple ones, not only because each device has its strong and weak points, but also since such approach will reduce the probability of damaging the stuff connected to the antenna; air-gap (spark) dischargers, gas tubes, antiparallel diodes, HV latch relays all have a place in such an approach

[floobydust]

The (snow on antenna) arcing occurring in Mr. Carlson's video with that 1937 FADA Model 360 tube radio, was happening after the 0.002uF antenna input capacitor, at the node B with the input transformer winding 36Ω DC path, to the chassis. So to be clear- it's AC coupled as far as the antenna is concerned, no dissipative resistors.
It seems to be a dipole antenna, coax with shield to one (not connected) element and other element center conductor to the radio.
But any other arc to the antenna elements would generate the fast pulse, a capacitive discharge possible from one element to the other that the radio antenna that was connected to.
So arcs can happen from other antenna hardware/elements I think, and there's still no coverage if using resistors or DC path.

[cdev]

How weird, I actually use a DC block now on my receivers input, unun


Thanks for telling me this, I am going to haveto add an RF choke there (por very large resistor) to allow the DC to be bled off..

I wonder if we'll see anything like that this winter. I would like to measure it - but without destroying my DVM!

The (snow on antenna) arcing occurring in Mr. Carlson's video with that 1937 FADA Model 360 tube radio, was happening after the 0.002uF antenna input capacitor, at the node B with the input transformer winding 36Ω DC path, to the chassis. So to be clear- it's AC coupled as far as the antenna is concerned, no dissipative resistors.
It seems to be a dipole antenna, coax with shield to one (not connected) element and other element center conductor to the radio.
But any other arc to the antenna elements would generate the fast pulse, a capacitive discharge possible from one element to the other that the radio antenna that was connected to.
So arcs can happen from other antenna hardware/elements I think, and there's still no coverage if using resistors or DC path.

  I wonder at what current that setup was capable of. In the video it made some noise, which takes some energy.

[David Hess]

A DC choke anywhere across the feedline can work to short out static charge assuming that it can handle the frequency range.  A moderate value of resistance works without resonance effects over a wider frequency range.  In either case the inductive or resistive element must sustain the voltage during transmit.

If the bands in use are harmonically related, then a shorted quarter-wave stub can be used to short out DC while allowing RF to pass.

How weird, I actually use a DC block now on my receivers input

The problem with just a DC block is that it will charge up until its breakdown voltage is reached, and then breakdown applying a high voltage discharge to whatever is behind it.  By itself this can make things worse.