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TA-FL Comms Telecon 202201-21 (draft) NVIS Comms HF 40m & SARNET Practice Thursday, January 21, 2022 5:30 PM EST Agenda • 40 meter+ communications net testing across Florida • Assess band conditions • Pick clear frequencies • Log sheet – evidence collection • Discussion Topics • SHTF protocol for amateur radio comms • Grounding for transient protection • Wrap Up • New topics • Suggestions FL State Licensees (2022-01-06) 40 meter bidirectional coverage established to date: - Pinellas County (St. Petersburg area) - Clay County (Jacksonville area) - Leon County (Tallahassee area) Compare to TA-FL regions coverage SHTF COMMS Plan • Drafting version for our use • Ref. AmRRON/Radiofreeq plan published in 2013 • https://radiofreeq.files.wordpress.co m/2013/11/shtf_frequency_list_2013 e_print.png • Will include various radio bands/modes/resources Grounding and Bonding Intro • Purpose: expose the amateur radio team to grounding best practices for protection of equipment from various types of surges • Discussion will be a shallow drive • Strategy: Grow your knowledge of protection methods over time, and implement enhanced protection methods as your assets grow Grounding Antenna Connections for Transient Suppression Comments • Electrical Bonding is the practice of connecting metallic objects that may be exposed to electrical faults or induced voltages to the grounding conductor. • Grounding is the attachment of bonded systems to the earth. • Bonding is crucial to maintaining low impedance path to ground Example: Vendor - Georgia Copper •Flexible Copper Grounding Straps •https://gacopper.com/022-strap.html •See links on website for excellent references • Surface preparation • Anti-oxidant • Brazing vs mechanical clamping • Objective: direct lightning energy to earth ground • Lightning surge protection uses different methodology than standard 60 Hz safety hazard protection • Model lightning as 100 kHz high voltage pulses • Wire, braid straps, solid straps are available for different purposes. Solid bonding straps perform better for lightning protection because of low impedance, skin effect, etc. • 1.5” copper strap is about $2/foot (100’ roll) • 3” copper strap is about $3.75/foot (100’ roll) • • • • 8’ ground rod every 16’ Cleaner and antioxidant applied to mating surfaces Stainless steel HW Buried strap Grounding Antenna Connections for Transient Suppression Grounding Antenna Connections for Transient Suppression • The next 4 slides are grounding guidance based on an ARRL referenced article from engineer CHARLES T RAUCH, JR (W8JI) • No interpretive liberties taken on the slides • http://w8ji.com/house_ground_layouts.htm • Use slides for future reference when pursuing your ultimate protection solution Grounding Antenna Connections for Transient Suppression 1 Poor but Commonly Used • The most severe and frequent damage is normally not caused by a voltage difference between each conductor in a multiple wire cable, but from those conductor groups or bundles to other conductor groups or bundles. Nearly all severe lightning damage is caused by lightning currents flowing through the house wiring as common mode current. • This first example has severe ground loops. It is a danger for many reasons. It does not protect for power line neutral faults, equipment failures, or lightning. • With a system like this, we should plan on damage when lighting strikes anywhere near electrical power lines or antennas. Drawing on Left • This system is the most common type of wiring used by Hams and CB'ers. It has a tower ground rod or rods, an equipment ground rod or water pipe connection, and an entrance panel ground at the electric meter. It does not comply with national electrical and fire codes, because it is independent entrance grounds. • The dashed line from the electrical service entrance panel to the radio room represents the power line leads in the house. • The heavier solid line represents all control and feed line cables from the antennas. • This is a very poor setup. Lightning protection, regardless of quality entrance protection devices that might be installed, will be almost nonexistent. Common mode lightning currents, the worse kind, will simply loop through equipment to the powerline. This is true if lightning strikes on or near power, CATV, or Telco lines, or if lightning strikes on or near your antenna system. Grounding Antenna Connections for Transient Suppression 2 Better but Not Perfect • This system adds a wide, heavy connection (shown as a thick black line outside house) between the entrance grounds. This connection could go under the house. My bonding connection, for example, goes directly under my house in the crawl space. I use 3-4 inch wide copper flashing with no splices or bends under the house. My bonding connection is kept away from other metallic objects like plumbing, ductwork, and wiring, even though it routes right under the house. • This bonding connection significantly reduces chances of damage from power line neutral faults and lightning strikes on the power lines or your antennas. This system meets national fire protection suggestions. (Although it is much better than the common isolated ground installations, lightning protection can still be improved.) • The nearer the radio room entrance panel and ground is to the electrical service entrance ground, and the lower bonding conductor resistance and impedance is compared to the impedance and distance of mains wiring to the radio in the house, the better this system will work! (Remember lightning has considerable higher frequency energy, treat it like RF.) • The dashed line from the entrance panel to the desk again represents all of the power and telephone lines. • The lighter solid line represents feed line and control lines. It goes through a grounded entrance panel. • The heaviest line is the bonding conductor. • Any desk ground wire should route parallel and near the operating desk to feed line and control wire bundle entrance panel to the feed line entrance panel. Do NOT run the desk ground directly to the station ground rod. • Remember while this is much better and meets codes, it is still not the best configuration. A portion of common mode lightning currents will still flow through equipment to the mains ground unless the radio equipment is unplugged or disconnected from all cables and grounds going to the entrance panel, or both. Grounding Antenna Connections for Transient Suppression 3 Better For Gear but Bonding Missing • This is another system that significantly improves protection of the equipment at the operating desk. Unfortunately it omits the critical ground bonding necessary for full house protection. It does NOT meet national code requirements. The mains ground is not bonded to the station entrance ground. • EVERYTHING on the desk or connected to the operating desk in the radio room has to routed from the room common point entrance to the desk. No exceptions! • The three lines from the panel to the desk are all of the power lines, a line representing all of the control lines and antenna cables, and the ground wire. • These lines can and should be bundled or closely spaced if possible. • The problem? While it forms a protection zone in the radio room, the path for common mode lightning currents between the antennas and the power lines is through house wiring! This can cause a large voltage difference between electrical wires and other metallic conductors throughout the house. Grounding Antenna Connections for Transient Suppression 4 Best by Far • This system meets all codes. This system is nearly as good as bringing all antenna system cables and wiring in at the house utility entrance (which would be perfect). • EVERYTHING on the desk or connected to the operating desk in the radio room has to run from the room common point entrance. No exceptions! • The closer the radio room cable entrance is to the power mains entrance, the more effective this system is. • The two lines from the radio room entrance ground panel to the desk include all power lines, with the medium size solid line representing a bundle of all control wires, all antenna cables and any desk grounding wire. These lines should be bundled or closely spaced. • Everything entering the desk area, including Telco and power connections, must be routed from the radio room entrance panel common point. • The value of the optional tower-to-station bonding conductor connection (longer dashed line) depends on distances. If the tower or antenna is near the house, it is better to bond it in. If the tower if more than 50 feet away, it might as well be isolated on its own ground because the impedance will likely be too high to be an effective bond. Types of Surge Arrestors/Transient Suppressors • Gas Discharge Tube • High voltage causes gas to ionize, conducting the current to ground • Energy discharge - highest • Response time - slow to trigger • Clamping voltage - 600V threshold for RF transorb (typ.) Types of Surge Arrestors/Transient Suppressors • Metal Oxide Varistor (MOV) • Resistance is lower at high voltages, causing current to discharge through device to ground • Most common • Many sizes, based on energy absorption capacity • Moderate energy discharge • Moderate trigger speed • Variable turn-on thresholds • Found in residential whole house protectors • Optionally mount in a service panel • Power strips, electronics products Types of Surge Arrestors/Transient Suppressors • Zener Diodes • Threshold voltage causes avalanche of current to discharge to ground • Lowest energy discharge • Fastest trigger speed • Variable turn-on thresholds • Electronics products Protection of AC line power at receptacle • Hybrid protectors have >1 type of device, including inductor and capacitor based filters • Multi-stage – see schematic • Example: Tripp Lite Isobar Outlet Surge Protector ($70) • MOVs, toroidal balanced chokes, ferrite rod-core inductors, VHF capacitors, thermal fuse • https://www.tripplite.com/iso bar-8-outlet-surge-protector12-ft-cord-3840joules~ISOBAR8ULTRA New Discussion Topics • Any member is welcome to brief a topic of interest • Examples • • • • • • • • • • • • • • • HF dipoles in trees, masts, field locations QRP and field operations Working with property restrictions (HOA) Grounding and bonding Beacons Digital modes NVIS review EMP and Faraday cages Portable generators Cool tools Repeaters and use cases (e.g., SARNET, local club repeaters, using GPS/databases) Programming Retevis RT devices Handheld Transceivers and VHF/UHF use cases CW (Morse Code) Others?