Thursday, January 21, 2021

Heathkit HM-2103 RF Wattmeter / Dummy Load - Part 2 - We're Finished!

 Got my "High Power RF Signal Generator" set up today, and attached it to the Heathkit RF Load.

The little Elecraft K2/100 I have is a pretty stable source for this use. The power control works smoothly to adjust the power from a Watt or two, all the way up to 100 Watts, and is stable. I made up a table of voltage vs power for the range I'd be using, and set things up in CW mode with my foot pedal plugged into the K2. The K2 has a built-in RF Power meter, but I've never properly calibrated it, so I used it to get close to the power level I wanted, and then read the actual RF Voltage it was generating, and then adjust the output power on the K2 to give me the RF Voltage I wanted.

The power formula is P = E^2 / R

If you rearrange things, you get E = sqrtPR

One of these days I'll learn the keystrokes for scientific/mathmatic symbols! easy one to remember is 50 Volts across the load equals 50 Watts of power applied. I made a table with some easy-to-hit numbers, and went from there.

Couldn't take pix of me doing it as that would have required four arms, but it calibrated "As Expected", and it's most likely calibrated better now than it ever was.

All back together and ready to be placed in service!

And I checked the Yaesu YP-150Z Dummy Load / Wattmeter, and it was so close I'll give it a pass. The specs for it are +/- 10%, and with my High Tech Calibration System, it read about half that, or 5%. Since it's "Better Than Advertised", I don't have the heart to break the seals on all three calibration controls inside in some half-a$$ endeavor to "Make It Better".

So tomorrow I'll drag the SB-401 Transmitter downstairs and uncase it for my forensic analysis. Since I'm pretty sure the same guy built both of these radios, I'm bracing myself for more coax replacement, more switch cleaning, more poor soldering and workmanship, and who knows what else. keeps me out of the bars at night!


  1. As long as your 'bill' for fixes doesn't exceed your bar bill, it's all good. :-)

    1. HAH! I hadn't thought about that, but you're right!

  2. Doesn't the wife unit wonder about the radio porn?

    1. Here on the blog, or down in the basement?

  3. OK, the radio tech's beyond me but... when they shut down the awesome internet of things to protect our hallowed democracy from domestic extremism, who's ahead of the game?

    1. I think you're alluding to alternative forms of communication?

      You can pretty much "talk" to the entire CONUS 24 hours a day, depending on how much you invest in your station, and if you want to use voice, or CW (Morse Code).

      The FCC just issued a notice stating that it's illegal to use Amateur Radio in the commission of a crime (it ALWAYS has been), and if you were tagged as a "Domestic Terrorist", they could pull your license, or refuse to issue you one.

      Make of that what you will.....


Keep it civil, please....