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Author Topic: RF Ground; the old chestnut...  (Read 1791 times)
EI4HQ
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Posts: 50


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« on: August 08, 2010, 02:33:58 AM »

Hi All,

Quick question. I'm in the situation of many many others in having my shack on an upper story. Now I've NEVER had any RFI issues. I have a 'serious' amount of copper in use inside and outside the shack and I'm using balanced antennas with common mode currents dealt with as far as practicality allows. However when all is said and done my 'RF ground' (sic) has to travel a distance of 4.14m from shack to ground rods. It's a 9" wide copper strip. Regardless, it's clearly going to show a high RF impedence at higher HF frequencies...

My question is driven more by curiousity than necessity (I stress again I don't have any apparent problems); my ground is:
  • x1.6 quarter waves on 10 metres
  • x1.4 quarter waves on 12 metres
  • x1.2 quarter waves on 15 metres
  • as near as dammit a quarter wave on 17 metres (clearly pretty uselss there)

On 10, 12 and 15 metres, is there any effective RF grounding taking place, or is an RF ground basically useless on all higher frequencies once the ground length exceeds a quarter wavelength?

Thanks in advance.

BR
Cormac, EI4HQ
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AA4PB
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Posts: 12770




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« Reply #1 on: August 08, 2010, 06:39:10 AM »

If you are using balanced antennas and have taken care of any common mode current issues on the feed line why would you need an RF ground at all? RF grounds are required when there is common mode current that needs to be shunted to ground.

Now, a lightning protection ground is a different issue. That should occur outside the house before the feed lines enter. It should be as close to ground level as practical.
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K3AN
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Posts: 787




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« Reply #2 on: August 15, 2010, 08:37:20 PM »

I concur 100% with AA4PB. When I became active again in the early 1980's I put in an "RF ground" for the station even though I was using a balanced antenna. The more I thought about it the more it didn't make sense. I've had eight QTHs since then (yes, we moved a lot!) and none of them had an RF ground for the equipment. A ground system for my inverted L? Absolutely, at the base of the L. But no ground for the equipment in the shack.
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