Friday, 22 August 2014

20dB or 40dB RF Attenuator

I have found that I need an RF Attenuator for my bench. My bench tools are primarily suited to QRP work and so whenever I have to mess with a 35W FM rig I find that my meters and sensors are inadequate. I've killed quite a few bits of test equipment by stuffing 50W of RF into a 5W power meter.

As part of a larger project to create a 0-500MHZ power meter I started with the attenuator. There's nothing special about this one other than perhaps the compact design. It can be either a 20dB or a 40dB device dictated by the resistors you populate it with. Indeed, if you buy the boards from oshpark.com you can make both variations for less than $5.
See how simple it is?

The attenuator will present a 50Ω load to the connected radio and with its 1/4W resistors should be good for small bursts of around 50W of RF. Adding 1/2W resistors should increase the power capability to 100W and allow for longer key-up times at lower powers.

The files are listed below in both Eagle and PDF formats.

20-40dB_RF_Attenuator.pdf
20-40dB_RF_Attenuator.brd
20-40dB_RF_Attenuator.sch

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