Using HF for EmComm: The Co Co County Experience
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Why HF for EmComm?
More than “When All Else Fails”: Historical Perspective
When the Grid, Cell Networks, and Internet are Down
Propagation Considerations: NVIS in Hilly Terrain
Solar Storms
Operational Usage: Antennas, Software, Hardware
Advantages of Diverse Modalities and Mostly Secure
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Propagation Considerations
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HF Antennas
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Ale antenna
ALE (Automatic Link Establishment) requires specific antennas to function effectively. Broadband Terminated Dipole (BBTD) antennas are ideal for ALE as they provide good SWR (Standing Wave Ratio) across a wide range of frequencies, from 160-10M.23 The Chameleon CHA TD is an example of a BBTD antenna that is suitable for ALE.2 Additionally, Barker & Williamson offers broadband HF folded dipole base station antennas that are useful for ALE, conventional, and NVIS (Near Vertical Incidence Skywave) applications.
For those looking for a single-band solution without a tuner, the EFHW-8010 is an End-Fed Half-Wave (EFHW) antenna that covers 80/40/30/20/17/15/12 and 10m bands, resonant on 80m (3.5MHz) and its harmonics, without the need for an antenna tuner.
Several resources provide information on ALE antennas, including HFLINK, which is an international resource for ALE and HF communications.23 For more detailed information and homebrew designs, you can refer to Bonnie KQ6XA's contributions on the HFLink.com website.
(contd)
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ALE Antenna (pg 2)
Several resources provide information on ALE antennas, including HFLINK, which is an international resource for ALE and HF communications.23 For more detailed information and homebrew designs, you can refer to Bonnie KQ6XA's contributions on the HFLink.com website
The main problem with ALEs is that it is a sponge for ambient noise which may increase your noise floor considerably.
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The geomagnetic field.
The orientation of Earth’s magnetic field is composed of two variables:
1. Earth's axis is tilted 23.5° to the ecliptic plane🗗
2. Earth's magnetic field is tilted 11° relative to the Earth's axis.
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The Interplanetary Magnetic Field (IMF) extends the Sun's magnetic field into space, carried by the solar wind. It interacts with Earth's magnetosphere, affecting geomagnetic storms and auroras
EARTH
Jupiter
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A TWO WAY STREET: Solar Phenomena as Friend or Foe
Solar phenomena can cause harm to GPS, Satellites, the Power Grid, EMPs, Gamma Rays, etc.
Essential Space Weather for Emergency Managers Final PDF: https://drive.google.com/file/d/1CLnLQm44_rXlu2M1sAHR9TRoSQ-PGz2d/view
Space Weather and Propagation Seminar and related files by NWS, NASA, and NOAA given on April 24, 2025 This is a subdirectory folder.
IS-66: Preparing the Nation for Space Weather Events
https://training.fema.gov/is/courseoverview.aspx?code=IS-66&lang=en
WISE USE:
Understanding Space Weather on the other hand facilitates EmComm
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The Extreme Ultra-Violet (EUV) wavelength generates the ionosphere
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HF modes provide increased privacy/security compared to FM voice
Morse Code (CW) best use of bandwidth (use 50 to 100 Hz filters. Can stagger stations less than 2 kHz apart. Best low signal punch (throughput).
SSB Requires at least 3 kHz spacing (good punch through)
VARA HF Fast, 3 kHz bandwidth – works well with Winlink
VARAC https://www.varac-hamradio.com/
Winlink Platform Very versatile platform https://winlink.org/
FLDIGi/FLMSG: Supports various digital modes https://www.w1hkj.org/
CW National Traffic System (NTS) – IATN (Intra-Area Traffic Net
Digital Traffic Net (DTN) https://radiorelay.org/wiki/digital-traffic-network/
JS8call http://js8call.com/
Packet (AX.25) and NETROM: A proven technology for over 40 years
PACTOR, AMTOR, ALE, SHARES https://www.cisa.gov/resources-tools/programs/shared-resources-shares-high-frequency-hf-radio-program
Useful HF Modes
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The Co Co County Story
Co Co County is divided into 4 regions (East, West. Central, and South). It borders Alameda County at Kensington, El Cerrito, San Ramon, and Lamorinda adjacent to Oakland, Berkeley, Albany, Dublin, and Sunol
Similar Terrain Design Considerations: Hilly, with valleys, trees, and ridges
A weekly VHF All County EmComm Net via the WA6HAM linked Repeater System
3 HF EmComm Nets Every Thursday 940m, 60m, and 80m)
15 local VHF/UHF weekly EmComm nets
HF liaisons connect local vhf/uhf and digital simplex nets in case internet, cell, an/or repeaters are down.
All these nets report to the County Wide VHF Net on Thursday night. The Net reports are issued on the Co Co County EmComm Groups.io forum.
Active local OAs run frequent SETs that coordinates Operation Areas (OAs) integrating VHF/UHF LANs, jurisdictions, and neighborhood GMRS nets with HF liaison stations.
County wide and Region Wide SETs have been curtailed by the lack of active County OES participation.
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Operational Usage: Management & Coordination
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Tactical: Location deployments to facilitate situational awareness, damage reports, evacuation notices, mutual aid, resource requests, and miscellaneous tactical traffic.
Where: Alameda County, Nearby Counties, Region II, State OES, Red Cross, Department of Health, etc.
Logistics: Evac centers, shelters mass care and reunification, animal relocation, NWS/Skywarn NTS/DTN health and welfare
Hardware: Antennas, Masts, power (battery backup & methods of recharging batteries), transmission lines, coax adaptors and connectors.
Jump Bags/Go Kits
Identifying Contacts, OAs Stakeholders, and Hardware
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Stakeholders/Clients in Contra Costa County
Walnut Creek, San Ramon, Lamorinda, and Martinez have established written or Verbal contracts (MOUs) with their jurisdictions; also, SATERN (Walnut Creek). The Richmond Comm Center Amateur Radio Team is sponsored by County OES as a CommU team. El Cerrito and Kensington have an informal relationship. The rest of county OAs need to renew or expand relationships with government jurisdictions.
An effort is being made to connect with local service groups, faith based groups, hospitals, and especially to/from citizens groups such as Firesafe, CERT, NERT, CORE, etc. A tiered system of GMRS LANs > GMRS/Ham ComHubs/ to local HamNet > to HF Net Liaison network is tested in SETs.
Co Co ARES is focusing on CERT/GMRS LANs via Comm Hub Centers with dual located ham/gmrs net operators facilitating tiered inter LAN EmComm and long distance EmComm
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NET TOPOGRAPHY: Liaison Interoperability
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Winlink HF, VARA C, VARA HF, are Arguably the most Robust Amateur Radio Digital Messaging Modes
For example, a severe solar storm that impacts upon a specific region of California and takes down the grid and satellite comms. Cell phones and internet are also down.
No problem, Amateur Radio battery powered HF stations equipped with Winlink or VARAC can connect to distant station outside of the blackout area and send messages. Any impacted OA can then also connect with any of these linked Winlink stations via HF on any HF frequency and receive the message.
Similar situations caused by earthquakes, extreme weather, storms, etc., are not limited to local power, cell phone, or internet connectivity using “WHEN ALL ELSE FAILS” technology.
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Designed Around Terrain Considerations and Interoperability
Three HF Nets every Thursday (40, 60, & 80 meters) and 15 local VHF/UHF nets weekly (except for the Digital Net which meets every other week).
CCC has 4 regions within CC County defined by geological location (East, West. Central, and South) It covers adjacent cities to Oakland, Berkeley, Albany, Dublin, Sunol, etc.)
HF liaisons/relay stations are assigned to local vhf/uhf and digital nets in case internet, cell, and repeaters are down.
All these nets report to a central County Wide Net on Thursday night. The Net reports are issued on the Co Co County EmComm Groups.io forum.
Active OA LANs run their own SETs that coordinates Operation Areas (OAs) integrating VHF/UHF LAN/WAN jurisdictions, and neighborhood GMRS nets with a HF liaison.
County and Region Wide SETs have been curtailed by the lack of County OES participation.
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Outreach and Training Activities
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LINKS
April 2025 Space Weather Presentation by NOAA, NWS, and NASA (subdirectory)
VARA HF and VARA https://rosmodem.wordpress.com/
VARAC https://www.varac-hamradio.com/
WINLINK https://winlink.org/
Underground Geoelectric Field Effects caused by CMEs
https://www.swpc.noaa.gov/products/geoelectric-field-models-1-minute#tabs-3
KAROECHO Website https://www.karoecho.net/
Presentation originally given to Oakland Radio Communication Association
May 3, 2025, by ni6a rev.2