Static discharge coupler

Status
Not open for further replies.

JMM-BDA

Member
Joined
Aug 7, 2008
Messages
40
Location
Bermuda
Firstly, I already have a HyperLink Lightning Surge Arrestor, followed by an ICE 304N Impulse Suppressor at the antenna end of my feed to handle any lightning hits, both of which will be grounded in the next couple of days.

My question here pertains to STATIC discharge at the other end of the feed, where it enters the house.

I've read some good posts on here, as well as links to articles, whereby it's described how to ground the actual feed cable (LMR400 in my case), by stripping away a part of the outer insulation to reveal the shield, and then to wrap a device around the shield & clamp tight, which in turn goes to ground.

I could be mistaken, but I seem to recall an inline coupler being available, which itself can be grounded. Using that item, I disconnect my N connector that feeds into the house from my antenna, insert this coupler at the end of the antenna feed, and then the other end of the coupler feeds into the house. I then connect a ground cable to the special attachment on the side of the coupler. So, it's basically an N-male to N-female coupler, but with an attachment on the side to which a grounding wire can be connected.

Am I imagining things, or does such a coupler indeed exist? If so, any leads as to which online supplier(s) I can get them from? I just assumed that such an item would be better than actually cutting open (albeit it only a small portion of) expensive LMR cabling.

Thanks in advance.
 

kb2vxa

Completely Banned for the Greater Good
Banned
Joined
Mar 22, 2005
Messages
6,131
Location
Point Pleasant Beach, N.J.
If you have discharge protection at the antenna and I don't see where it's needed on a VHF/UHF antenna and the mast is well grounded you don't need it anywhere else. Static buildup on small elements is minimal unless you have to contend with wind blown dust in a desert environment like the Army found out the hard way in Desert Storm. Now if you have a lot of wire in the air like an HF dipole or long wire it can become charged by an approaching thunderstorm. In that case a gas discharge arrestor is a good way to go.

DO NOT strip the coax jacket and allow moisture and contaminants to enter! If you really want to ground the shield properly install a Cushcraft Blitz Bug lightning arrestor and ground it. All exposed connections should be securely double wrapped with vinyl electrical tape, moisture is thine enemy. Another caveat, never crimp or crush the cable and allow the recommended minimum or larger bending radius to prevent conductor migration. This and other data is supplied by the coax manufacturer and is available on line.
 

JMM-BDA

Member
Joined
Aug 7, 2008
Messages
40
Location
Bermuda
That's the problem with a lot of the ads you see these days. For example, some of the companies selling lightning arrestors state that their products, well, protect you against lightning. Other companies tell you the same thing, but also tell you that those same items also discharge static. I assume that all of those items protect against static as well. So for novices such as myself, it would be nice if they're more descriptive.

The ground on the arrestor I have is on the outside (the shield side), so I assume that's where the static would be, as opposed to the inner core of the cable.

As for the potential for static here .... the humidity is way too high for normal static, but we do get high winds from time to time ... in the range of 150+ mph (i.e. yearly hurricanes).

Thanks for your warning about never cutting open the jackets of coax. I've seen quite a few online vendors selling kits which tell you to do just that. Much appreciated.
 

fineshot1

Member
Joined
Sep 17, 2004
Messages
2,499
Location
NJ USA (Republic of NJ)
Thanks for your warning about never cutting open the jackets of coax. I've seen quite a few online vendors selling kits which tell you to do just that. Much appreciated.
That would be for hardline(not LMR400) and said kits do contain methods of re-sealing up the outer jacket for hardline once the hardline sheild is properly grounded at the entrance point main ground bar.
 

kb2vxa

Completely Banned for the Greater Good
Banned
Joined
Mar 22, 2005
Messages
6,131
Location
Point Pleasant Beach, N.J.
"The ground on the arrestor I have is on the outside (the shield side), so I assume that's where the static would be, as opposed to the inner core of the cable."

Actually the arrestor provides a discharge path from the inner to outer conductor which being grounded safely bleeds charges above a given potential to earth. The Blitz Bug is an arc gap while a gas discharge arrestor contains what amounts to a neon tube that conducts at a much lower voltage. The "arc plug" part of it is replaceable as it will only withstand so many hits and a big one will destroy it.

Like I said you really don't need these things for small VHF and UHF antennas, grounding the support structure is quite sufficient. If this is impractical then grounding the outer conductor of the coax where it enters the structure is imperative and in compliance with the NEC, that's where the Blitz Bug comes in handy. It has a ground lug for attaching the earthing wire which is a whole lot easier for the novice than bonding it to a double SO-239 as I have done a few times.

As a footnote, professional installations on towers have not only the tower grounded but the coax shields bonded to the tower at it's base making for one continuous conductor, thus eliminating any difference in potential between the transmission line and tower. Alternately they may pass through a grounded bulkhead where they enter the equipment shack which is bonded to the tower base. Still I saw a TV weatherman holding a microphone jump and shout when lightning hit the broadcast tower. (;->)

Oh Fineshot, not all hard line has a vinyl jacket, sometimes it looks from the outside to be plain old copper water pipe. I remember the day I helped the CE of a local radio station repair holes in the transmission line after hearing gunshots and the transmitter kicked off and wouldn't reset. Tubing cutter, blowtorch and solder in hand replacing the damaged sections was more like a plumbing job than anything else. Calming the GM screaming over the phone was another matter entirely, a matter of diplomacy.
 
Last edited:
Joined
Nov 5, 2006
Messages
635
Location
Phoenix Arizona
NOTHING will protect your radio from a direct lightning hit when it goes down the center conductor, as logic would suggest. Static buildup aside, there is another issue here, and that is lightning induced surges. Basically, enough electricity is present due to a NEARBY lightning strike that it goes down the line and fries the front end or worse. The "lightning protector" protects somewhat against NEARBY strikes, but of course does nothing to help with a direct strike. The term is a bit of a misnomer I suppose.

Those who have a lightning protector and a lot of nearby lightning will notice the gas tube blackening over time and they will need to replace it when as it gets darker. Eventually it will just short the center conductor to ground.
 
Last edited:
Status
Not open for further replies.
Top