Grounding Radios

[wuzafuzz]

CUL's and other radio heads:  The most recent issue of The Sentinel described an incident in which a cadet was zapped (not injured) while working in a comm trailer, and blamed a lack of proper grounding.

Given that our SAREX's and events are usually in borrowed buildings, I'm not about to pound an 8 foot grounding rod into the ground (or a parking lot.)  I'm curious what others typically do to ground radios and antennas in a temporary install.

[Airrace]

If you can place something into the ground purchase the following items from your local hardware store:

10 feet piece of 3/4 " copper plumbing pipe
Electrical pipe ground connector
#10 electrical wire (length depends on how far your trench is from the radio)

Attach the electrical connector and wire to the 3/4 " copper pipe.
Dig a trench at least six inches deep and place the copper pipe in the ground and cover over with dirt. Make sure to frimly place all the dirt back over the 3/4" copper pipe. You will also need to wet and tamp the ground over the copper pipe.

Then hook up the wire to your radio.

[Airrace]

You can also place rock salt over the pipe prior to placing the dirt on top. This will help!

[Airrace]

I have a three foot ground rod that I attach to my power source (generator). You don't need to drive a ten foot rod into the ground.

[wuzafuzz]

Thanks for the info Airrace. 

What if you can't find a place to drive a ground rod?  I'm thinking of scenarios where I'm setup in an FBO surrounding by asphalt and concrete, or in a trailer in a parking lot.

[Thom]

Thanks for the info Airrace. 

What if you can't find a place to drive a ground rod?  I'm thinking of scenarios where I'm setup in an FBO surrounding by asphalt and concrete, or in a trailer in a parking lot.

You know, someone here might know a good answer, but I know where I'd start asking, and it isn't CAPTalk...

http://www.usraces.org/

http://www.ares.org/

http://www.arrl.org/

Surely the guys at those places have experience with running radios in 'inhospitable' environments.  Probably much more so than CAP, though I bet we are right behind them and ahead of a lot of other organizations/agencies.

Thom Hamilton

[Al Sayre]

Clamp to a Pad Eye on the ramp.  They are usually connected to a huge mesh of steel screen embedde in the concrete...

[Airrace]

If you have a metal building nearby that also can used as a good ground. Just place a clamp to the metal building.

[RADIOMAN015]

The best grounding in the world isn't going to stop the radio or the operator from getting fried if there's a near miss or direct hit by lightening.  This might add a false sense of security    Perhaps when there's thunder it's time to disconnect the antenna from the equipment and turn off the radio!

When we are using the radios & have cadets & seniors out in the field durint squadron ES training night on our reserve base, I make sure if there's even a slight chance of bad weather that our simulated mission base (squadron radio base station) call base weather for an initial report & depending upon that report (probability of lightening) will get 1/2 hour updates.  Good practice for the comm team.

RM   

[Major Lord]

To say that the Cadet was shocked due a a ground problem does not really address the root problem. Does this mean that the cadet was shocked because a piece of equipment that he touched was hot in relation to ground, due to an internal power supply problem ( or design problem) or because he touched a wire that was hot while at the same time being in contact electrically with ground? If the Com Trailer was set up properly with a shore-power plug, then there should not be a "ground" problem. Not all conditions causing electrical shocks are due to ground problems, and of the few that are, copper ground spikes are not likely to be the cure. If you need to physically mount radios and antennae in a temporary install, You should be able to grab a perfectly good AC ground from the AC plug, or if not available ( Its hard to believe that there are some places in the US old enough to have AC outlets without ground tabs!) grab a ground from a cold water pipe or water spigot.

An RF ground is a different animal entirely. HF antennas may require an enhanced ground, usually at the antenna site, especially for vertical antennae not having sufficient radials. Keep your cotton picken hands of RF radiators! These can shock and burn you , and unlike Gamma radiation, you won't develop superpowers as a result of exposure.

I can just imagine my local FBO as I whip out the old sledge hammer and start driving spikes into the tarmac......

Major Lord

[wuzafuzz]

Thanks for all the ideas!  Contacting ARES/RACES types is a good idea since they do this stuff all the time.  I'm under no illusions grounding a mast and coax will prevent all damage from a direct lightning hit, but do want to try to be safer and comply with regs.  Unfortunately the regs don't seem to anticipate setting up a comm shack in anything other than a permanent installation.

Mobile radios are so much easier...

[Airrace]

The only way to prevent damage from lighting is to install a surge arrestor. I recomend them on any tower due to a lighting strike. You can purchase them at any wholesale electrical supply dealer.

[RiverAux]

For those who didn't go read the Sentinel referred to in the original post (SHAME ON YOU!):

At a wing encampment this year, lightning struck a communications
antenna mounted on a trailer parked adjacent to the building being
used as the encampment headquarters. The strike damaged several
pieces of equipment. A cadet was using a laptop at the encampment
headquarters and experienced an electrical shock. Luckily the cadet
suffered no lasting side effects, complications or restrictions to duty.
The investigation revealed neither the antenna nor the trailer was
grounded. According to CAPR 100-1, Communications, paragraph 7-1b,
Equipment Grounding: "All communications equipment not in motion
will be adequately grounded at all times." Paragraph 7-1e states,
"Lightning arrestors or grounding switches should be installed on all
antennas."

[desertengineer1]

I share the same basic concern as Major.  Instructing someone to pick the nearest metal pipe can be more dangerous than having no ground at all - for reasons that are more complicated than I have time to explain here.

The key word is SINGLE POINT GROUND when dealing with power.

ANY grounding of electrical equipment should be done with guidance by properly trained and qualified individuals.

Grounding is NOT a catch-all solution to electrocution hazards, and in most cases of injury, a ground would have not prevented the incident.

Most electrocution cases result from multiple failures of improperly installed or modified equipment (Hot/Neutral wires swapped or open cabinets), or by use of equipment not designed for electrical safety or not compliant with UL/NEC/NFPT. 

I am not happy to see this Safety entry.  It could propigate a false assumption that (1) Grounding of equipment is all that is required, and (2) propigate misinformation that can be more unsafe as no ground at all.

Earth ground, if not tied to a single point ground, can be very dangerous to personnel and equipment if a lightning strike or major power event occurs.  Resistance of earthen ground is high between two points.

I think I'll be sending an email up the chain on this one.

To say that the Cadet was shocked due a a ground problem does not really address the root problem. Does this mean that the cadet was shocked because a piece of equipment that he touched was hot in relation to ground, due to an internal power supply problem ( or design problem) or because he touched a wire that was hot while at the same time being in contact electrically with ground? If the Com Trailer was set up properly with a shore-power plug, then there should not be a "ground" problem. Not all conditions causing electrical shocks are due to ground problems, and of the few that are, copper ground spikes are not likely to be the cure. If you need to physically mount radios and antennae in a temporary install, You should be able to grab a perfectly good AC ground from the AC plug, or if not available ( Its hard to believe that there are some places in the US old enough to have AC outlets without ground tabs!) grab a ground from a cold water pipe or water spigot.

An RF ground is a different animal entirely. HF antennas may require an enhanced ground, usually at the antenna site, especially for vertical antennae not having sufficient radials. Keep your cotton picken hands of RF radiators! These can shock and burn you , and unlike Gamma radiation, you won't develop superpowers as a result of exposure.

I can just imagine my local FBO as I whip out the old sledge hammer and start driving spikes into the tarmac......

Major Lord

[desertengineer1]

The only way to prevent damage from lighting is to install a surge arrestor. I recomend them on any tower due to a lighting strike. You can purchase them at any wholesale electrical supply dealer.

NEGATIVE.  The only way to prevent damage is to not have electrical equipment at all.

The most efficient, risk reduced, methods are to follow NEC and NFTP procedures and codes when equipment is installed.  Again, lots of details here I can't go into fully.

This includes, but is not limited to:

1.  Single point ground to get as close to equal potential as possible.  Refer to NEC or NFTP.

2.  Grounding of antenna and transmission line at points specified in code.  This varies depending on structure and EES characteristics.  Again, ask someone who is trained and qualified.

3.  Yes, use of a surge arrestor is one link - but remember those ONLY protect from transient events that are nearby.  THEY DO NOT protect the system from a direct strike.  See #2 above.

4.  FOLLOWING ALL PROCEDURES FOR LIGHTINING HAZARDS.  This should be addressed in your communications or safety plan (Hopefully both and they are the same).

[desertengineer1]

We do the following when lightening is estimated within 10 miles or thunderstorms are immenant:

1.  Disconnection of all coaxial cable from radio equipment not installed in a mobile configuration.

2.  If installed in a communication trailer or temporarily running into a window, cable is removed and laid near the antenna.  This reduces the potential of a strike path entering into the structure.  If a direct strike occurs (especially in the case of a tactical antenna in a tree or temporary pole), the energy is most likely to stay in the antenna structure/line area.  This will melt the cable, but less likely to take the equipment or personnel with it, or set fire to the building.

3.  Personnel are removed from the radio equipment area and sheltered accordingly, if able.

You don't want to be anywhere near radio systems if theya re connected to tall metal objects.  Best to go inside the FBO or hangar and drink coffee until the storm is over.

[Al Sayre]

Most hangars are tall metal objects, so stay away from the walls and supports if you use one for shelter...

[desertengineer1]

OOKKK.

1.  Grounding of the trailer with a copperweld rod may have had little effect on the hazard.  Note my use of the word MAY.  If the ground rod and item connected to the rod is not tied to the single point ground of the 120 VAC system per NEC, the hazard is increased.  You now have a big resistor between the rod and the single ground point.  A direct or nearby strike can result in thousands of volts of potential between the ground rod and the electrical ground or neutral line.  Again, consult someone qualified and trained!!!

2.  Direct strike of an antenna has a HIGH probability of damaging equipment regardless ground or surge arrestor installation.  In the case of #1 above, a floating ground rod can actually increase the chance of damage, and injury to other personnel elsewhere.

3.  "Adequitely Grounded" should be clarified.  What defined adequite?  I would give a resounding NO to using the nearest water pipe!  Now you have possibly the same situation I described in #1.  If the building plumbing entry point is not tied to the equal potential ground point, you could have immense potential between the plumbing and any nearby electrical equipment.

TO ME, "adequitely grounded" means connection from ground lugs on the equipment to the single ground point of the structure or trailer.  In the case of a comm trailer, there should be a location marked as such.  The ground rod and all equipment goes there.

Second - why were personnel in the trailer using electrical equipment tied to AC power to begin with?  This should be a lesson to everyone.  Stay away from AC fed equipment, wired phones, and plumbing during a storm!!

For those who didn't go read the Sentinel referred to in the original post (SHAME ON YOU!):

At a wing encampment this year, lightning struck a communications
antenna mounted on a trailer parked adjacent to the building being
used as the encampment headquarters. The strike damaged several
pieces of equipment. A cadet was using a laptop at the encampment
headquarters and experienced an electrical shock. Luckily the cadet
suffered no lasting side effects, complications or restrictions to duty.
The investigation revealed neither the antenna nor the trailer was
grounded. According to CAPR 100-1, Communications, paragraph 7-1b,
Equipment Grounding: "All communications equipment not in motion
will be adequately grounded at all times." Paragraph 7-1e states,
"Lightning arrestors or grounding switches should be installed on all
antennas."

[desertengineer1]

Hey Mike - I vote this thread be moved over to Safety.

[desertengineer1]

Negative.

Connect the ground to the single point ground lug of the comm trailer.

Connect radios to the single point ground lug.  Recommend daisy chain them (all on one single line) using #6 stranded, non-insulated, or green color if insulated.

If you can place something into the ground purchase the following items from your local hardware store:

10 feet piece of 3/4 " copper plumbing pipe
Electrical pipe ground connector
#10 electrical wire (length depends on how far your trench is from the radio)

Attach the electrical connector and wire to the 3/4 " copper pipe.
Dig a trench at least six inches deep and place the copper pipe in the ground and cover over with dirt. Make sure to frimly place all the dirt back over the 3/4" copper pipe. You will also need to wet and tamp the ground over the copper pipe.

Then hook up the wire to your radio.