One thing to be wary of with these inexpensive step attenuators is they may not provide a 50 ohm input impedance. I bought a similar one (different brand) on eBay and it worked fine, except that the input impedance changed a LOT with the attenuation amount. I finally decided that was too dangerous for use with any rig and bought a really nice Bird 100W 30dB attenuator (only $60 on eBay) instead, which has a perfect 50 ohm impedance and a perfect 30 dB attenuation. That brings even a 100W (50 dBm) signal down to 0.1 W (20 dBm), at which point you can use inexpensive fixed attenuators. You can buy 10, 20, and 30 dB fixed attenuators that handle < 2W for only a few bucks on Amazon. They have true 50 ohm input impedance and seem to be calibrated pretty well. So combine a big fixed 30 dBm attenuator with a small 30 dBm attenuator and a 100W signal is down 60 dB to -10 dBm (0.01W), which is safe for the TinySA.
Rob
