Pulled out my dummy load tonight

Press image for a better view of the dummy load

Testing a transmitter means the use of a dummy load. Trying to be considerate, I don’t want to cause unnecessary interference with my signals. So when I want to test my Ultimate 3 QRSS/WSPR kit I also pull out one of my dummy loads.

It measures just 9-10 mm across and is the size of a BNC connector. It is simply one of the many Ethernet terminations that I have lying around. Its built-in 50 ohm resistor is rated at something like 0.25 W. Considering that the kit outputs something like 200 mW that should mean that there is enough margin and no forced air cooling or liquid cooling is required.

These terminators were used with 10BASE2 or 10BASE5 ethernet. They are not so common anymore so the terminators are not that easy to find any longer. But they are still very handy for testing QRPP transmitters.

The size of these dummy loads should point out in a very vivid way how tiny the power levels of these transmitters are. Despite that, when running with the effective WSPR code, they can still be decoded on the other side of the globe.

Showing just the back of a piece of equipment is contrary to my bragging instincts, so for completeness, the front of the Ultimate 3 QRSS/WSPR kit is also shown. It is housed in the minimalistic, but beatifully crafted acrylic enclosure from M0ION.

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Sverre Holm, LA3ZA, is a regular contributor to AmateurRadio.com and writes from Norway. Contact him at [email protected].

4 Responses to “Pulled out my dummy load tonight”

  • w3fis, Paul:

    I have been able to get those 50 ohm terminations at Radio Shack, as well as a local computer store. They also make nice “dust caps” for things like my FT-817ND when in the field, to prevent damage to the BNC fitting.

    73 /paul W3FIS

  • W8MRL:

    Do you get spotted often using qrss? Where should I monitor and what software do I need?

    Thank you,

  • LA3ZA, Sverre:

    Actually, I have never tried anything but WSPR and that’s why I bought it in the first place. There is a yahoo groups, QRPLABS, for this kit where your question may be answered.

  • BX2ABT:

    Ah, 10base2….my first encounter with computer networking. I spent way too much time setting up my first network using 10base2 because of this sh1tty OS called Win98. It was the reason I switched to Linux and I never looked back.

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