Lightning protection... A little help here???

Robert HT220 · Post by **Robert HT220** » Tue Oct 28, 2003 5:58 pm

I know this topic has been covered before, but here we go anyway. I have a question concerning lightning protection. I have a VHF base antenna set up, about 15ft in the air, running about 25-30ft. of RG58 coax to a PL259 which is hooked up to my VHF Mostar. Right now I have no lightning protection whatsoever. What do you guys reccomend doing here? I think there is some in-line thing that hooks up to the back of the radio, and has a terminal on the side that is supposed to run to a ground wire????? I can't spend much on this as I don't have much to spend.

The system works great, I just don't have a base power supply. I had to test it with a car battery.LOL

Sure don't want a car battery in my room.

Anyway, someone have any suggestions?

Thanks

Robert

nmfire10 · Post by **nmfire10** » Tue Oct 28, 2003 6:08 pm

What is the antenna attached to?

fire-medic8104 · Post by **fire-medic8104** » Tue Oct 28, 2003 7:10 pm

The thing you are referring to Robert is commonly referred to as a polyphaser. The tab off the side is to use a nut and bolt and either secure to a ground plate or a ring terminal and a ground wire.

jim · Post by **jim** » Tue Oct 28, 2003 7:30 pm

Don't forget- ground antenna, coax, Polyphaser, radio, power supply all to ONE common point as per National Electrical Code's minimum requirements. Motorla and other companies have great info available on grounding.

Good reading:

http://www.polyphaser.com/ppc_pen_home.asp

jbxx · Post by **jbxx** » Tue Oct 28, 2003 8:12 pm

I use an argon arc device called a transi-tap.
Never had one hit yet, so I can't really speak
to the effectiveness.
J.B. AD6WX

RKG · Post by **RKG** » Tue Oct 28, 2003 8:42 pm

There are two separate grounding actions for an external antenna. The device you refer to, a Polyphaser, is used for shunting high voltage that might come over the center conductor of coaxial cable. However, in a near strike, you are more likely to have high voltage coming down the outer connector, and for that you use a so-called "grounding kit," which connects to the outer conductor and goes directly to a grounding rod at the base of the tower or structure. There should be at least 2 grounding kits on each feedline: one at the first bend aloft and one at the last bend where the feedline enters the building. (It is at the bends that any lightning-induced current is likely to jump off the conductor.)

Note that these devices are effective, if at all, only for induced currents resulting from near strikes. If your antenna take a direct hit, there is nothing that is going to do any good.

Motorola has a published standard for grounding (I forget the number, but it is in the public domain and freely available); this is considered an industry standard for grounding external antenna systems.

Added: Motorola Specification R-56.

Jim202 · Post by **Jim202** » Tue Oct 28, 2003 8:51 pm

Some people think that lightning protection brushes on witch craft. Others say it is an exact science. Some will say you can't protect your equipment from a direct strike and others say you can.

I for one, after working in the radio field for over 35 years, probably plant my feet someplace between these positions. I have seen towers take a strike and all the radio equipment at the tower stayed up and on the air.

It's kind of strange being near a tower in the rain and actually see a bolt hit the tower. The tower steel will steam for a few minutes in the rain after the strike, untill it cools enough.

How does one survive shuch a strike? By taking great care in the installation of the grounding SYSTEM. You notice I used the term SYSTEM. No one thing by itself will do the job. It takes a good low resistance ground on the tower, antenna, coax cable, radio equipment, electrical power and telephone lines.

You install a good power line surge protector, a telephone line surge protection, ground kits on the coax cable and coax surge protectors near your equipment.

Part of the most important issue is to keep everything at the same potential during the strike. If eveything is at the same potential, then there is no current flow. It's when different parts of a radio system have different potentials between them that damage occurs.

Cellular sites take strikes all the time and come away still operating. They do spend a good deal of money on the grounding system. They put in a ground ring around the tower, another ring around the equipment shelter or platform and tie the two rings together in at least 2 places. The electrical meter ( neutral ) ground is also tied to this same ring ground. The telephone company also ties their cable protection to the same common ground.

The towers will have a ground tied to each leg. On a good installation the ground wires will be exothermically welded to a tab on the tower legs. On the poorer installations, you will see some form of a mechanical clamp connecting to the tower legs. A guyed tower will have a couple of ground rods grounding the guy wires at each anchor points.

This may not be the answer you were looking for, but it will give you some thoughts on just what you may want to look at on your antenna system. Just how far you go will depend on just how secure you want your radio to be. It may also depend on how good you insurance is.

Jim

nmfire10 · Post by **nmfire10** » Tue Oct 28, 2003 8:52 pm

RKG wrote:If your antenna take a direct hit, there is nothing that is going to do any good.

A CO2 or Halon extinguisher might be of assistance??

RKG · Post by **RKG** » Wed Oct 29, 2003 6:52 am

More likely a vacuum cleaner.

Robert HT220 · Post by **Robert HT220** » Fri Nov 07, 2003 3:29 pm

Thanks for the info. I really don't use it a lot, I use my MT1000 almost every day. The Mostar will probably get de-commisioned and put in my pickup and I'll just use the antenna for a scanner antenna.

Robert

k4wtf · Post by **k4wtf** » Fri Nov 07, 2003 3:42 pm

nmfire10 wrote:
RKG wrote:If your antenna take a direct hit, there is nothing that is going to do any good.
A CO2 or Halon extinguisher might be of assistance??

Halon == illegal and outmoded. You want CO2 or FM200 now.

--
John

nmfire10 · Post by **nmfire10** » Fri Nov 07, 2003 5:20 pm

k4wtf wrote:
nmfire10 wrote:
RKG wrote:If your antenna take a direct hit, there is nothing that is going to do any good.
A CO2 or Halon extinguisher might be of assistance??
Halon == illegal and outmoded. You want CO2 or FM200 now.

--
John

It's still around, lots of it. While I don't have any, I see Halon extinguishers around all time. In fact, all of our computer centers (big ass ones at that) have halon systems in them.

KG4WMS · Post by **KG4WMS** » Fri Nov 07, 2003 6:48 pm

The production of Halon ceased on January 1, 1994 under the Clean Air Act, it is still legal to purchase and use recycled Halon and Halon fire extinguishers.

nmfire10 wrote:
k4wtf wrote:
nmfire10 wrote: A CO2 or Halon extinguisher might be of assistance??
Halon == illegal and outmoded. You want CO2 or FM200 now.

--
John
It's still around, lots of it. While I don't have any, I see Halon extinguishers around all time. In fact, all of our computer centers (big ass ones at that) have halon systems in them.

Cowthief · Post by **Cowthief** » Sat Nov 08, 2003 7:56 pm

Hello.

The other thing you may want to remember is the Height Above Average Terrain.
If you have an antenna that is 15 feet in the air, and all the overhead power lines are 25 feet in the air, the chances of a hit are very slim.
One of the reasons cell sites survive is that the antennas are usually several feet from the top, where the actual strike occurs.
Just like the lightning rods that were common on farmhouses, you can divert a strike, keeping your radios, or farmhouse, from going up in smoke.

OX · Post by OX » Sun Nov 09, 2003 5:37 am

nmfire10 wrote:
k4wtf wrote:
nmfire10 wrote: A CO2 or Halon extinguisher might be of assistance??
Halon == illegal and outmoded. You want CO2 or FM200 now.

--
John
It's still around, lots of it. While I don't have any, I see Halon extinguishers around all time. In fact, all of our computer centers (big ass ones at that) have halon systems in them.

If Halon was installed before the laws changed, it becomes a grandfathered system. Modify it at all and you have to replace it though.

FMROB · Post by **FMROB** » Sun Nov 09, 2003 11:44 am

Bubba is right,,,,,Most states have adopted the int'l Fire Code which expressly states that once the system is altered or If the system can no longer be serviced it has to be replaced with a UL300 system. A word to the wise, almost all of the companys that produced a halon extinguishing system almost immediately ceased production, replacement parts, and service training ultimately making the system unservicable, thus the code would make it be replaced. As with all fixed pipe fire suppression system they must be maintained every 6 months by a qualified service techinican,,,My guess NMFire your system will be next for the "non-compliance" tag and a visit by the local fire marshal.

P.S. I wouldn't suggst being in the room at the same time of the discharhe of a halon system, the gas depletes the O2 within the almost airtight room. And yes, it also does something to the ozone...

Just a heads up..Rob

nmfire10 · Post by **nmfire10** » Sun Nov 09, 2003 12:10 pm

Well, I don't believe it is for the room itself. I it is for under the floor. The floor is a raised deck kinda thing and all the wires are under it. It activates when the smoke and fire sensors under the floor detect the wires burning.

Believe me, everything is extremely up to code in this place as far as alarms go.

Lightning protection... A little help here???

Lightning protection... A little help here???

HAAT.