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Author Topic: Alternative to a Ground Rod  (Read 2608 times)
NS8Q
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Posts: 135




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« on: July 04, 2012, 01:16:53 PM »

Is there a simple alternative to provide some sort of ground in the shack?  I was reading about using a piece of wire connected to the tuner that is less than 1/4 wavelength of the highest band, which is my case is 10m.  Do you think that will eliminate the RF getting back into the shack, especially in the USB cables connecting the computer to the rig and Signalink USB sound card interface?

73
Chris NS8Q
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G0GQK
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Posts: 634




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« Reply #1 on: July 04, 2012, 01:37:09 PM »

A ground rod will not prevent RF affecting equipment in your shack, You need to buy ferrite clamps and ferrite rings to attach to the various cables which are connecting your computer and tranceiver. I have never used a ground rod and the recommendation to use one is a fallacy which has been within the ham fraternity for years !

Mel G0GQK
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NS8Q
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Posts: 135




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« Reply #2 on: July 04, 2012, 01:43:33 PM »

Great idea...I forgot about those.  I had a satellite radio receiver that had some ferrite beads on the cable.  I'll give them a try.  Thanks.
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NS8Q
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Posts: 135




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« Reply #3 on: July 04, 2012, 01:46:00 PM »

Are you thinking of something like this....

http://www.radioshack.com/product/index.jsp?productId=2103222


or...

http://www.radioworks.com/crfi.html
« Last Edit: July 04, 2012, 01:48:14 PM by NS8Q » Logged
WB6BYU
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Posts: 13335




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« Reply #4 on: July 04, 2012, 06:15:28 PM »

The best way to eliminate the RF is to locate the source:  it could be due to common mode
currents flowing on the outside of the coax (in which case ferrite chokes on the coax, or
proper decoupling at the antenna, will help), or the radiated RF from the antenna is simply
too strong and the USB wires are acting like antennas and picking it up.

Are you using an OCFD perchance?
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NS8Q
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Posts: 135




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« Reply #5 on: July 05, 2012, 06:59:12 AM »

Yes I am.  It's about 35 feet up running parallel to the house.  I am using a line-isolator at the feed point of the antenna per the recommendation of the manufacturer.

I've never had trouble with RF in the shack computer, just with the computer downstairs and the Stereo.  I installed a low-pass filter and it took care of the problem.  It's interesting because the shack is upstairs, closer to the antenna.
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G8JNJ
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Posts: 493


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« Reply #6 on: July 05, 2012, 12:08:19 PM »

Hi Chris,

These notes may be of help.

http://webzoom.freewebs.com/g8jnj/EMC%20and%20Amateur%20radio.pdf

Regards,

Martin - G8JNJ

www,g8jnj.webs.com
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K0ZN
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Posts: 1553




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« Reply #7 on: July 05, 2012, 10:09:18 PM »


 OCF's are notorious for RF in the shack issues.  You see lots of comments/complaints on here if you go back.

 Agree with BOTH previous ideas.  (1.) add some ferrites.  (2.) take additional actions to get the RF off the OUTSIDE of the shield.

 No matter what kind of balun, etc. you put at the antenna, the antenna IS unbalanced with respect to the coax shield. Period.

 Another possible solution can be (viewed as coming down from the antenna) to run the coax through a 3 to 5 ft. piece of
 conduit or copper pipe which has low impedance/short wire/strap going to real earth ground, then a choke coil of coax (8 or 10 turns, 8 to 10 in. in dia.)
right after the "feed through capacitor" made from the tubing. The idea here is to capacitively drain the RF from the OUTside of the shield to ground.
There is also some small amount of lightning protection afforded by that set up.

73,  K0ZN
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