Examples of Work on Electronics
Amateur Radio Station -- K1TMA
In the last month’s issue I discussed the purpose
of a grounding system and its effec- tiveness in relation to an antenna
system. Ground is the other half of an antenna. Near the end
of my article I brought up the subject of the relationship between the
various grounding systems: Bus Bar Ground, Bulkhead Ground,
System Ground, Tower Foundation Ground, Guy Wire Ground, Electrical
Ground, Plumbing Ground and the Commonality Ground to connect each
ground to each other.
Bus Bar Ground -
In the Bus Bar Ground, which is behind of all the radio equipment on the radio desk, the obvious purpose is to provide an immediate ground for all of the equipment.
Each rig, whether a digital transceiver, communication receiver, heavy power supply, etc., has a “grounding lug” in the rear. Place a 1/2 inch to 1 inch wide copper braid from the “grounding lug” in back of the rig to the Bus Bar. It should not be more than 12-14 inches long.
To ensure good conductivity between each “grounding
lug”, on the Bus Bar and the copper braid, use a small amount of “conductive
grease” on both the “grounding lug” and around the hole, to accommodate
the outside diameter of the “grounding lug” on the braid
In the middle of the Bus Bar there should be a hole in the metal to accommodate another “grounding lug.” Attach the appropriate size high-voltage copper solderless lug to a 4, 6 or 8-gauge multi-strain copper wire (no smaller than 8 gauge) and then attach the solderless lug and wire (the “system ground wire”) to the Bus Bar. Use conductive grease for the same reason as before. Make the physical connections tight for the same reason. Now the “system ground wire” is ready to go outside to connect with the “system ground” immediately outside of the house and as close as possible to the radio shack. Remember, the “system ground wire” is the heavy gauge wire between the Bus Bar and the System Ground, usually not more than a few feet in length and rarely longer than 10 feet. If it should be too long and begins to resonate with the operating frequency of your radio station, it will act as an “isolation transformer”, through an over-powering increase in impedance, and effectively remove your RF ground from your radio station. Then your station will have no RF path to ground to complete the RF circuit. RF energy will come back to your equipment (searching for a path to ground). It is easy to tell when it happens. Everything is “hot” to the touch. All metal components will have a tinkling sensation to the touch and some of the meters will jump as you touch and remove your finger. When ground works effectively there will be no such sensation; the metal chassis and box will not radiate RF energy and instead serve as an effective electrostatic shield from interference, from other RF sources, and effectively prevent RF components inside of the chassis and box from interfering with components and systems outside of the chassis and box.
The Bulkhead Ground -
This grounding system is uniquely different than all of the other grounds. Though it still provides a path to ground, its real ultimate purpose is to provide a commonality of a path to ground for all or most of the accessory equipment, such as surge protectors, RF lightning arrestors, power distribution panel and fuses, low pass filter, band pass filter, AC lightning arrestors and telephone line surge protector and lightning arrestor for your computer in the Shack.