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Author Topic: System grounding when running off battery power  (Read 650 times)

WW9DLM

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System grounding when running off battery power
« on: September 26, 2021, 06:02:00 AM »

Hi there,
Looking for advice for grounding systems during field day or emergency comm's when operating off of batter power (or gen power).

Here is what I am thinking, so please chime in with advice.
On the folding table, I would have an 18 inch piece of copper pipe with 3 bolts and wingnuts to attach all equipment grounds to it. Then run a #12 wire (15 feet) from the copper pipe to a 4 foot ground rod, 3 foot of it in the ground. The ground rod would also have a bolt with wing nut for the wire connection.

Also, I will be using 20 foot of fiberglass poles to elevate a Diamond X50 antenna, (or similar) for communications. Do I need to ground any part of that antenna to the same ground rod (say using #12 wire)?

I plan on using a VHF radio, HF radio & a tuner on the table. I do not expect to be out in bad weather.

Any suggestions would be greatly appreciated.
Thanks in advance.
73's,
Dale
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K0UA

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Re: System grounding when running off battery power
« Reply #1 on: September 26, 2021, 07:41:28 AM »

May I ask what you intend to accomplish with the grounding setup? In other words, why are you doing this?
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73  James K0UA

KD6VXI

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Re: System grounding when running off battery power
« Reply #2 on: September 26, 2021, 09:44:06 AM »

The whole ground rod is useless.  You would be fine bonding everything to the pipe on the table.

But the rod is pretty much useless.  You don't need ground for your antenna or radio equipment to work.

You'd be better off investing the money in a pair of feedline chokes.  One at the output of your swr meter or tuner and the other at the feed point of the antenna.

--Shane
KD6VXI
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WW5F

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Re: System grounding when running off battery power
« Reply #3 on: September 27, 2021, 03:57:13 AM »

Battery:  (12V?) You're probably good to go without an "earth reference" for a temporary setup.  Worst case is you might get burned by RF if you touch something with the right random configuration.

Generator:  (120/240V?) I would advise having an "earth reference."  Worst case is you might get killed touching the right/wrong thing at the wrong time.

The subject of grounding is always a subject of debate.  This is just my advise.  You can take it or leave it.

Grounding reasons:

1.  Personal Safety
2.  Lightening protection
3.  Reference
4.  Electrostatic Discharge
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W9IQ

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Re: System grounding when running off battery power
« Reply #4 on: September 27, 2021, 05:02:20 AM »

Dale,

When doing em-com work, in my experience, you rarely get to choose the weather conditions!

In general though, Shane is right that a couple of good common mode chokes could help a great deal in keeping RF from getting to the radio and keeping local RFI out of your receiver.

Antennas can develop large static charges from wind and from seemingly distant thunderstorms. So you should consider some type of static discharge capability at a minimum. You may not always have the chance to deploy a proper grounding system but often several long wires along the ground along with a proper lightning arrestor can do in a pinch.

With that being said, most of us operate mobile or portable without any type of proper earth ground system. It generally is not required for the antenna so judicious operating conditions keep us out of trouble and our radios working.

- Glenn W9IQ
« Last Edit: September 27, 2021, 05:05:01 AM by W9IQ »
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- Glenn W9IQ

God runs electromagnetics on Monday, Wednesday and Friday by the wave theory and the devil runs it on Tuesday, Thursday and Saturday by the Quantum theory.

WW9DLM

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Re: System grounding when running off battery power
« Reply #5 on: September 27, 2021, 10:29:43 AM »

Hi Guys,
Thank you everyone for your advice.
I already purchased a choke from Chameleon to go with the EMCOMM II antenna.

So for the VHF/UHF side, I'm not sure what choke to purchase? Can someone point me in the right direction? I will be using RG-8x coax for the dual band radio/antenna.

I will probably use a coax grounding system (from DX) to ground the coax from the antenna. And a copper pipe nearby to ground all the gear together. I understand when using a generator that an earth ground would be very helpful.
Thanks everyone,
Dale



 

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KD0REQ

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Re: System grounding when running off battery power
« Reply #7 on: September 27, 2021, 02:51:40 PM »

for static dissipation, a quick-and-dirty is solder a 2-watt resistor into a PL-259, use a T to connect that and the antenna to the rig. I've got a 47K in mine, won't burn up from the RF it siphons. won't do squat for any other form of knob-bite but I used to get stung a lot in my Novice days from wind in the wires.
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W9IQ

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Re: System grounding when running off battery power
« Reply #8 on: September 27, 2021, 03:06:18 PM »

A high impedance shunt element such as a resistor will have no useful effect on an ungrounded system. A low Q inductor may be a better choice.

- Glenn W9IQ
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- Glenn W9IQ

God runs electromagnetics on Monday, Wednesday and Friday by the wave theory and the devil runs it on Tuesday, Thursday and Saturday by the Quantum theory.

WB6BYU

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Re: System grounding when running off battery power
« Reply #9 on: September 28, 2021, 06:12:48 PM »

The only time I've bothered with grounding when operating
portable, it was to stick a BBQ skewer in the ground to drain
the static charges off the antenna.  (The capacitors were arcing
over every few seconds without it.)  But that was a pretty
highly charged time:  other than something like a kit supported
wire, it is rare to have that much static buildup (at least not
without wanting to take shelter from potential lightning).

(I've mostly operated from areas where lightning is rare, and
would avoid operating if it there was a potential storm.  But
lightning protection for a portable station is a much bigger
project.)

If you have problems with the rig being hot with RF, then you
need to fix your antenna.  Adding a quarter wave radial to the
tuner case, or using an effective balun, often will fix the problem,
although a choke alone isn't always adequate to suppress the
common mode current if it doesn't have an alternative path.

For a VHF antenna on a mast there is no need for station grounding,
unless you are tempting lightning, then you shouldn't be
there anyway.


Unless you can clearly articulate the reason why you are
adding grounding, there may not be any benefit to it.

AA4HA

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Re: System grounding when running off battery power
« Reply #10 on: October 01, 2021, 09:06:09 PM »

I was knocked on my arse when doing a radio field test for a SCADA system in an electric utility right of way. The overhead lines were 500KV, the antenna was 20' up in the air and attached to a fiberglass rod. It was a 900 MHz 10 dBi Yagi antenna with a piece of LMR-240 running down to a point where I could attach a test radio.

Two guys raised the mast like you would for raising a flag over Iwo Jima and were standing there holding it steady (and to rotate the yagi) and I grabbed the end of the coax to plug it in. It was like being zapped by a stun-gun and it put me on my backside. That was just the stray EMF almost 100 feet below those overhead lines.

Yes, even for a dinky little antenna I will ground it with something

Tisha Hayes
Senior Engineer
AA4HA
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Ms. Tisha Hayes, AA4HA
Lookout Mountain, Alabama

WW9DLM

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Re: System grounding when running off battery power
« Reply #11 on: October 07, 2021, 07:02:40 PM »

Hi there,
Thanks again to everyone for responding. My intention for grounding the antenna/mast was for static build up in the antenna. Also to keep all grounds on all the equipment connected together. I did end up using a copper pipe about 2 foot into the ground, and a ground wire to the base of the mast where I had a coax connection junction. This would take any static build up to the ground and not into the radio. My intent was not for lighting protection.
Thanks,
Dale
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KB8VUL

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Re: System grounding when running off battery power
« Reply #12 on: November 07, 2021, 09:29:09 PM »

You ground any station the same way. 
Single point of ground that EVERYTHING gets bonded to.
While the standard is keeping all grounds as short as possible, this is not feasible for field operations.

First go find a ground bar.
Cut random lengths of number 12 wire crimp lugs to it for both a radio connection and connection to the ground bar.
Get a concrete hammer drill and a ground rod driver for the same. 
Get a length of number 6 or larger wire to run from the rod to the bar. 

When you get to the site, put the bar in the middle,,, driver the rod with the hammer drill and connect the wire to it. 
Ground all radios and antenna masts to the bar. 

When you are done, you can either pull the ground rod with a hi-lift type jack and a chain or disconnect the wire and drive the ground rod below grade and leave it there.

Where the power is sourced from doesn't matter when you are talking about grounding.  The grounding isn't there to protect you from the power source.  It's there to protect you from  isolation failures in equipment, static buildup and other situations that the chassis of a radio or other equipment can become energized and flow that voltage potential to ground with a lower resistance than through your body.

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US7IGN

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Re: System grounding when running off battery power
« Reply #13 on: November 08, 2021, 12:07:11 AM »

I don't know much about this, but just in case, I always stick a metal pin into the ground, to which I connect the body of the radio station. It's quick and easy.
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