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RF Suppressor Ground System

Apr 16th, 16:51

KK6CXF

Joined: Mar 13th 2013, 10:36
Total Topics: 0
Total Posts: 0
I too have a 2nd floor "shack" grounding issue, with a length-to-ground rod distance of about 17-18- feet. I have heard about a system published in 2003, that addresses electrical & RF grounding by using RG-8 coax with a capacitor at one or both ends of the coax. The length of the coax between the ground rod and ground bus at the equipment is then, not an issue. Does any of this make any sense. I know at least one retailer who sells capacitors for this "system" and have also had another ham retailer recommend it.

Tom KK6CXF
Apr 17th, 13:21

W1VT

Joined: Apr 4th 1998, 00:00
Total Topics: 0
Total Posts: 0

The best way to handle the second floor shack grounding issues is to run coax from the antenna to single point ground that is line of sight and bonded to the electrical service entrance, and then bring up the coax to the 2nd floor station. Some antennas, such as verticals and long wires, may require a good radial system for decoupling, as ground rods are typically inadequate. A balanced antenna, like a center fed dipole, will often work with just ground rods. A half wave dipole is likely to be the easiest antenna to get working well from a 2nd floor station.

A program like EZNEC can be used to model this type of ground. The outside shield of RG-213 coax can be modeled as a 0.4" solid copper conductor. You can then connect a transmission line of the appropriate velocity factor (0.66 for solid polyethylene up to 0.84 to foam) to model the center conductor and inside of the shield. While you can't "prove" anything, you may learn enough to satisfy your curiosity, or justify spending the time and effort to make a few measurements with real hardware.

Zack Lau W1VT
ARRL Senior Lab Engineer

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