GREEN VALLEY AMATEUR RADIO CLUB
  • Home
    • Repeater Info
    • OUR Web SDR
  • Projects
    • 13.8 Volt Load
    • Antenna Ideas
    • Antenna Construction Ideas
    • Dummy Load
    • Past Projects >
      • Organization
      • RFI Mitigation >
        • Direction Finders
      • 2 Meter Gallery
      • Vertical Flagpole
      • Magnetic Loop
      • Wire Antennas
      • SDR Dongles
      • On the Ground Loop Antenna
  • Activities
    • Calendar
    • NETS >
      • Sunday - Two Meter Net
      • Tuesday - Oatmeal Net
      • Thursday- N7GV Simplex Net
      • Wednesday - Snow Bird Net
      • Inactive Nets >
        • Monday - DMR Net
    • Contests >
      • Winter Field Day
      • 7qp
      • Field Day
      • Arizona QSO Party
    • Social Time Out >
      • Wednesday - Breakfast
      • Thursday Evening Dinner
    • Picnics
    • Special Events
    • Titan Missile Museum
    • Driveouts
    • Road Cleanup
    • Parks on the Air
    • HamFest 2025
  • About
    • 2025 Board Members
    • 2025 Committees
    • Meeting Minutes
    • For New Members
    • Get Help
    • Ham Radio Sites
    • Classes & VE Testing
    • CW Interest
    • Ready, Set, Go Info >
      • Ready, Set, Go
      • Your Go Kit
      • My Alerts
    • Donations of Radio Equipment
    • History
    • Gallery
    • GVARC Certificates
    • EchoLink
    • BaoFeng HTs
    • Contact Us
    • We belong to ARCA
    • Miscellaneous >
      • Emergency Plan
      • Links
      • Technical Blog
  • Members
    • Ham Gear for GVARC Members
    • Current Roster
    • GVARC Logo Items
    • Inventory
    • Members We Honor
    • Name Badge Request
    • DMR Info
    • Win System
    • Member Profiles

Dummy Loads

Almost all radio transmitter tuning and testing requires a test termination usually at 50 ohms. You will find that sometimes a very accurate load is required with many available “dummy loads” failing the test at high frequencies or various power levels. And some of them are more expensive than one would expect. I came across an answer when I heard about thick film resistors. In this project I use two Ohmite 100 watt 100 ohm resistors in parallel providing a very accurate 50 ohm load at outputs over 100 watt, perhaps up to 200 watts for short time periods.

There’s nothing very pretty about this unit. It is constructed of scrap aluminum plate donated by a local Club member, a chunk of aluminum angle, some stainless steel hardware and a UHF connector. (Thanks to all of you who offered material) A 50 ohm BNC or N connector should be used for accurate results above 2 meters. In this case several small pieces were laminated together to create sufficient mass to dissipate heat using SS bolts, tapping the receiving plate so no nuts were used, the heads are countersunk and heat sink compound used after cleaning the adjoining pieces.

The pictures show the simple construction front and back.  A housing could be placed over the resistors for protection, but is not really necessary.  I apologize for the fuzzy picture of the VNA scan.  However, you can plainly see the blue trace SWR is 1 to 1 from 1.5 mHz to 900 mHz and the yellow trace impedance is flat 50 ohms. 

This is a very useful tool for any shack that is easy to build at a low cost. The resistors are roughly $10 each, the rest is scrap box material.

N9MW 3-16-23

Picture
Picture
Picture
  • Home
    • Repeater Info
    • OUR Web SDR
  • Projects
    • 13.8 Volt Load
    • Antenna Ideas
    • Antenna Construction Ideas
    • Dummy Load
    • Past Projects >
      • Organization
      • RFI Mitigation >
        • Direction Finders
      • 2 Meter Gallery
      • Vertical Flagpole
      • Magnetic Loop
      • Wire Antennas
      • SDR Dongles
      • On the Ground Loop Antenna
  • Activities
    • Calendar
    • NETS >
      • Sunday - Two Meter Net
      • Tuesday - Oatmeal Net
      • Thursday- N7GV Simplex Net
      • Wednesday - Snow Bird Net
      • Inactive Nets >
        • Monday - DMR Net
    • Contests >
      • Winter Field Day
      • 7qp
      • Field Day
      • Arizona QSO Party
    • Social Time Out >
      • Wednesday - Breakfast
      • Thursday Evening Dinner
    • Picnics
    • Special Events
    • Titan Missile Museum
    • Driveouts
    • Road Cleanup
    • Parks on the Air
    • HamFest 2025
  • About
    • 2025 Board Members
    • 2025 Committees
    • Meeting Minutes
    • For New Members
    • Get Help
    • Ham Radio Sites
    • Classes & VE Testing
    • CW Interest
    • Ready, Set, Go Info >
      • Ready, Set, Go
      • Your Go Kit
      • My Alerts
    • Donations of Radio Equipment
    • History
    • Gallery
    • GVARC Certificates
    • EchoLink
    • BaoFeng HTs
    • Contact Us
    • We belong to ARCA
    • Miscellaneous >
      • Emergency Plan
      • Links
      • Technical Blog
  • Members
    • Ham Gear for GVARC Members
    • Current Roster
    • GVARC Logo Items
    • Inventory
    • Members We Honor
    • Name Badge Request
    • DMR Info
    • Win System
    • Member Profiles