Measuring HamShield Power Output

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Measuring HamShield Power Output

Update: we now sell our Wideband Power Meter here!

We have been asked a few times for information on measuring HamShield's power output in a cost effective way. While there are a variety of instruments available, most are well out of the budget range of a hobbyist. Sure, a simple analog power meter is cost effective, but a lot of them are not optimized for displaying power output under 1 watt (+30 dBm).

This can make it a bit challenging for validating the power output out of any QRP radio, not just HamShield.

So, naturally, we built our own!

Using the board is quite simple: You just plug an RF source into the SMA connector and read the power output on your computer. The power levels are sent over USB serial to a terminal program, such as CoolTerm. A program running on the Atmel Mega32U4 runs a simple program to collect data from Analog Devices' HMC713 power detector to make it all work. 

While it supports a maximum of 20 dBm (about 100mW), you can add an attenuator (say 10dB) and increase the maximum power you can detect. It would be pretty easy to calculate, since you just add 10 to the resulting dB value.

You could probably measure crystal oscillators, exciter circuits, output from a DDS IC, various radio modules, etc.

Is this something you could use too? Let us know in the comments. It might just be a new product someday!


  • Casey Halverson

    @Rich Right now, its software written in AVR Studio, but it could easily become Arduino compatible with a little work.

  • Rich Paleski

    With a decent directional coupler this could be used at any power level. With outputs from a forward and reflected coupler, reflection coefficient can be measured instaniously. What software exists for this product?

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