OCHEART Simplex Coverage 202003282220

OCHEART Simplex Exercises


In April 2020, several members of OCHEART planned a field exercise to test simplex communications between hospitals and simplex relay sites throughout the county.

In the weeks prior to the exercise, OCHEART members Mark Warrick (KM6ZPO) and Julie Warrick (KN6AOC) visited 14 potential simplex sites.  Afterward, Mark mapped out the simplex locations and hospitals, including photographs and RF maps for each simplex site.  Based on the RF predictions he found using the website https://heywhatsthat.com/, Mark then generated RF maps and spreadsheets of likely reachable points between hospitals and simplex sites.  Mark wrote the exercise plan for the two days of drills, recruited, and mobilized the team.

Belmont Park View


As stated in the lesson plan, the purpose of the exercises was:

  1. To test communications between simplex sites and hospitals.
  2. To test communications between simplex sites.
  3. To practice relaying traffic.

For the exercises, the team deployed to five hospitals and seven simplex sites over two days, including a rainy day that added a degree of practical complications (i.e. some didn’t have equipment to shield themselves and their equipment from the rain), to conduct communications drills over simplex frequencies.

Each of the drills simulated real-life practice of a catastrophic event encompassing a total breakdown of repeaters, phone systems and even the power grid itself.  All participants were using battery-powered systems with some having only 5-watt handheld transceivers.

After the tests, the participants submitted logs of what they experienced in the field.   The results were pretty much as predicted.  The tests confirmed the viability of the simplex sites tested and revealed that handheld transceivers using only a whip antenna were not effective for simplex sites.  Furthermore, it was determined that even a 5-watt radio could be effective if paired up with a good antenna.  Location, terrain, and elevation were obvious big factors for clear simplex transmissions.   The predicted success chart of simplex to simplex sites and simplex to hospitals sites was accurate.

For future consideration and exercises, Mark Warrick wrote an article about types of antennas that could be used in the field which you can peruse on his website: http://km6zpo.com/antennas-for-emergency-communications/


In the coming months, OCHEART plans to do more planning and exercises including:

  • Surveying each hospital site to determine readiness of existing equipment and staff.
  • Additional exercises to test all the other simplex sites and hospitals not tested.
  • Digital transmission exercises (WinLink and NBEMS).


To support future endeavors, the OCHEART leadership team has decided to create a special team of operators dubbed the “HILLTOPPERS”.  This to-be-formed team of operators will be the first responders in the field, setting up the communications infrastructure at simplex sites when an activation occurs for the purpose of enabling the critical communications infrastructure needed between all the hospitals.  More information will be announced on that soon.


The OCHEART leadership team thanks all the members who participated in the drill, including:

  • Art Remnet (KM6RSY)
  • Bob McCord (K6IWA)
  • Dale Tyler (W6EDT)
  • Dave Southworth (KS6RFI)
  • David Black (WB6VEM)
  • David Gorin (KB6BXD)
  • Jeffrey Rosenthal (W6BIK)
  • Julie Warrick (KN6AOC)
  • Mark Warrick (KM6ZPO)
  • Roger Hamilton (KK6LZB)
  • Ronald Mosher (K0PGE)
  • Scott Holcomb (K6WHC)

Watch the members-only Volunteer Signups section of the OCHEART website if you wish to participate in any of the future plans.

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