Minimal Grounding at Events
I was at our Skywarn Recognition Day this year, setup at the local NWS office of course, just as I am every year. We had our antennas all setup, equipment all setup, then at some point later in the evening someone pointed to a box of wire and said "we forgot to ground the equipment!" and about half the people began frantically trying to wire up their rigs.
Now, here is what the "grounding" consists of:
- 4 foot ground rod driven about 2 1/2 feet into the ground
- About 12 feet 3/8" braid (maybe less, like 1/4") running from the rod to a bus bar (like those used in breaker boxes)
- 4 2-3 foot pieces of solid 12awg wire connected to the bus bar, each with a spade connector.
Someone asked me if I wanted to ground my rig. I looked at the mess of wire and just said "no thanks". There wasn't even enough to ground every piece of equipment. I mentioned it probably wouldn't do any good. Only 2 people grounded their equipment.
Later the next day, as we started tearing down, someone pulled the ground from one of the rigs when someone was still listening and he says "whoa, my noise just went away!"
So anyway, from everything I've read, it seemed this "grounding" was pretty much pointless and maybe even likely to do more harm than good. Does that sound right? Am I missing something that what they had a valid reason to ground that way?
I know this could turn into a jab fest, but I'm seriously asking. Maybe someone can give me a quick explanation as to why it wouldn't work that I could easily pass along to the group.
Just a side note, it was about a 50/50 split between who agreed they needed grounded and who didn't, so half of us were right
Thanks and 73,
If it was balanced antennas they were using then the ground would have been superfluous.
The only useful thing that comes from pounding a rod 2½ feet into the ground is exercise. As Paul G4LNA said, a balanced antenna makes anything else unnecessary. If there's any issue with the rig's chassis being hot with RF, a ¼ wavelength wire tied to the chassis takes care of it.
Great, thanks for the replies! We were using pretty much all dipoles and 1 loop. Note that there was no grounding in place for any of the coax, tuners, switches, power supplies, just the rigs themselves.
I figured it really only contributed to exercise Thanks for the assurance that I'm not crazy!
The criteria is not just a "ground" but a low impedance RF ground. Big difference and, no, 2 ft of rod in the ground does not constitute a low impedance RF ground.
The only time an RF ground is needed is when it is the "other half" of an unbalanced antenna system. What is an "unbalanced antenna system" ? ? A good example would be an end fed quarter wave vertical. In a situation like that, a two foot rod pounded into the ground would NOT do a bit of good. That antenna would require a good field of 14 wavelength radials, extending out from the feedpoint in all directions, in order to really have a good RF ground. Many hams try to get away with less, and sometimes think they have a good setup, but that is only because they have not compared what they are using to a REAL good antenna system. Again, as Paul G4LNA said, a balanced antenna makes anything else unnecessary.
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Its about as barmy as the prats over here who install new bathroom suites. The law states that the sinks must be earthed, grounded for US listeners, so what do they do when the house has plastic plumbing ? Ha ha ha, they put earth straps on the plastic pipes.
When I told the sales person (sic) that its impossible to make an earth on a plastic pipe he looked at me as if I was out of my mind and said that building regulations have to be obeyed because there are heavy fines if they don't comply, Ha ha ha.
And.... they employ people to visit and inspect the work to see that the earthing straps have been attached to the plumbing. They're all mad !!
Remember, however, there are actually THREE "ground" systems involved in an Amateur Radio installation!
1. The "RF" ground. As stated, with a balanced antenna system, it may not be necessary... With many vertical or random length wire antennas, it's ABSOLUTELY necessary for proper or effective operation.
2. The "Safety" ground. If equipment is operated on battery power, it's not a significant consideration; if operating from mains (i.e., commercial power) it IS an important and necessary requirement.
3. The "lightning" ground. THAT may be the MOST important; if you have a significant antenna erected, even if for a temporary (Skywarn event being ironic) period, lightning protection can be VERY necessary; direct hits are not the only hazard; even nearby strikes can cause significant damage to radio equipment.
The ground you described only served to provide a return path to ground for noise that didn't have a path before, creating a 'ground loop' that increased the noise level. It was a crummy return path for noise, too.
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