Tuesday, March 13, 2018

The subject of grounding

In the past weeks I had some questions about interference on VDSL2 modems and another question  if grounding would be necessary. So I was searching in my blog archive as I have been studying the subject several times. And even after studying, I could do some things wrong. So this is a small list from my previous articles about grounding and/or a shack earth point.

https://pe4bas.blogspot.nl/2013/08/shack-rf-ground.html
https://pe4bas.blogspot.nl/2013/09/the-rf-surpression-ground-system-myth.html
https://pe4bas.blogspot.nl/2014/11/shack-rf-combined-earth.html
https://pe4bas.blogspot.nl/2013/11/making-second-floor-shack-ground.html

And this is what happens with static electricity build up when a thunderstorm is nearby. The reason why I have a ground at my antenna entrance.

https://pe4bas.blogspot.nl/2016/07/shocking.html

Not that I always have a clue what I am talking about, but at least I try....
Best written articles about grounding can be found at

http://www.w8ji.com/ground_systems.htm

And even I made a fault to include a knife switch in my installation which was completely unnecessary.

So what I've learned:

- A ground in your shack which is bonded to a earth electrode is for safety. It is not a RF ground.
- Use a entrance panel for your coax and other cables that is grounded well outside the house.
- If possible ground your antenna supporting mast as well
- Prevent earthloops, they are a source of much RF problems.

A good tool for measuring is a simple multimeter. If you seem to have problems anywere try to find that second or even third uneccessary ground connection and remove it. Remember that the shield of your coax is ground as well. So a extra wire for example from your radio to the entrance panel is only giving you a groundloop and so, this is not necessary at all. For grounds sake, less is better in grounds case!

Think about this: Most of the mains grounds are bonded to the case of a appliance. In our case as radioamateurs we always have a power supply which is bonded through the ground via the mains connector cable. Most computers have this ground as well on the same mains net. A extra ground wire from the computer to your ground is not necessary (ground loop again). However, if you do digital modes you have your soundcard connected to your radio, is the ground from your connectors grounded to the mains ground in the computer? You could have a problem (ground loop). In my case the ground of my mains connecting cable is also bonded to my negative pole on the 13,8V output in my Astron RS-50A power supply, I've had a lot of groundloop problems before I discovered this. That's why measuring with a simple multimeter is important! 


Ground paths in my shack...green strokes are grounded.
Above the main net supplies, 12VDC supplies, coax and ground paths in my shack. My power supply has no galavanic connection to the main electricity net. The computer does however. Nothing is connected to main net safety earth. Everything is connected to the shacks own earth electrode which is bonded to my entrance panel. There is no separate earth wire connection to the entrance panel, I trust the coax shield is my earth connection. However, if a thunderstorm is nearby I disconnect the coax from the entrance panel leaving my equipment un-earthed. But that's no problem as I always switch my mains net off in the shack (have 2 master switches for both wall outlets) in that case. The central earth point is there but is only connected to a counterpoise which is existing of strokes alu foil tape below the floor. The radio is earthed through the coax connected to the Palstar tuner.

I don't say the above writing is the truth and nothing else. It is like other posts for archive purposes as well. I might think completely different in a couple of years...at least I've the feeling I'm safe this way.

2 comments:

  1. The RSGB's RadCom magazine got themselves into a total mess when they tried to cover station grounding last year. Their author didn't take into account that, in many places, the incoming mains electricity supply ground function is provided not by a separate earth wire, but along the neutral wire (a 'protective multiple earth' system). In some cases, like a storm, the neutral can break, and so therefore can your earth protection. If you have an RF earth point installed for a radio or something, then you are legally required to connect it to the mains earth point (running to neutral in this case), where it comes into the house and the cable must be a minimum 10mm2. If you don't you could find that your RF earth becomes the only grounding point for a number of properties in your immediate area, which could reach fire-generating current levels!

    The RSGB completely failed to include this, and I was one of several who complained about the danger of writing such an article. They printed that there was an error (but not highlighting what it was) inviting qualified people to write a correction, but I have not seen such a correction being printed.

    The RF earth in my shack is properly installed for an earth/neutral break condition, and all equipment is bonded to the same copper pipe in the ground point to provide a common zero reference.

    ReplyDelete
    Replies
    1. As far as I know protective multiple earth is not allowed in the Netherlands. My "RF" earth point is not connected to the mains earth point. All equipment in my shack is earthed on a separate earth in my case, as you can see in the diagram. However, I disconnect ground when I remove the coax from the entrance panel. But since I switch off all electricity to the shack when a thunderstorm arrives it is not dangerous. At least, that is my view on it. Still grounding is a difficult subject even for professionals. 73, Bas

      Delete

Thanks for your comment. Bedankt voor je reactie. 73, Bas