Aluminum for grounding and bonding instead of copper?

Discussion in 'General Technical Questions and Answers' started by N0RDE, Jun 27, 2021.

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  1. N0RDE

    N0RDE Ham Member QRZ Page

    Wow, thanks for the responses! Copper is expensive and gets out of sight when you look at stuff much larger than you need. Turns out 6 ga is more than adequate. Pain in the wallet but not quite as bad... The goal is to provide protection to my shack and HF antenna. The antenna is a 73 feet long Chameleon installed in backyard as an inverted L (35 feet vert 38 feet horiz). At the base there will be a ground rod and lightning arrestor. The common ground is a Ufer about 80 feet away with at least on 90 deg turn.

    Questions:
    1-How many ground rods are needed?

    2-Would running the bonding wire in small PVC pipe close to or attached to foundation be acceptable? We are in CO near Denver and any trenches would have to be about 3 feet deep due to freezing.

    73 de N0RDE Jon
     
  2. KC3TEC

    KC3TEC Ham Member QRZ Page

    if you do an earth resistance test you would wet down the soil and put the probes 35 (2 probes) feet apart and one to a ground rod for a total of 3 points
    it requires the use of an earth resistance meter
    an earth resistance meter is like a megger on steroids and will pump a lot of voltage into the ground between the probes, (1000volts and sometimes larger ones produce 10 kilovolt or more)
    then display the resistance,
    you want to try for 25 ohms,
    but realistically that may be quite difficult. ( ground conductivity depends highly on its moisture content and the percentage of mineral salts in the soil, iron rich soil has a much lower resistance than many clays and sandy soils.
    generally 2 ground rods are required but you may need more pounded in.

    earth resistance test are usually done for engineering purposes by power companies (lineman) and specialty electricians, its not usually done by most contractors.
     
    Last edited: Jun 28, 2021
  3. N0TZU

    N0TZU Platinum Subscriber Platinum Subscriber QRZ Page

    If you haven’t already, read the “sticky” thread in the Antennas forum that lists many resources on grounding, number one being the highly recommended ARRL grounding and bonding book.

    I don’t know anything about Chameleon antennas, but if it’s a traditional inverted L it needs a counterpoise - in this case since it’s ground mounted, some radials in the ground which are part of the antenna. Those radials don’t need a ground rod to function at RF and by their nature provide a decent path to ground for lightning to help dissipate it. Since there doesn’t need to be a rod at the antenna then you don’t need to bond anything back to the house ground system - other than the coax at the house end obviously.

    Also, because of the distance involved, it doesn’t make a lot of sense to me to try to keep the antenna counterpoise at the same potential as the house ground during a nearby lightning event because the inductance in the ground bonding wire would prevent it anyway, even with rods along the way. Nobody can touch the antenna 80 feet away at the same time they touch something grounded at the house, or put one foot near the house ground and one near the antenna.

    But be aware Code requires that if a rod is used at the antenna that it be bonded back to the house ground.
     
    Last edited: Jun 29, 2021
  4. N0RDE

    N0RDE Ham Member QRZ Page

    N0TZU and everyone who has responded,

    Thank you! My copy of Bonding and Grounding has disappeared. Bet I find it within a day of buying a 2nd copy...

    73 de N0RDE Jon
     

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