I really do not want to blow up my new toy


I have just obtained a shiny new DSA815-TG (the new one with the 10Hz RBW) and mostly due to the price am very keen not to blow it up. Here are my thoughts so I would appreciate any suggestions if I have anything wrong.

I intend to put the output of a small handheld Yaesu transmitter (1 or 3 watts) through a 20DB attenuator, then a mini-circuits ZFDC-20-5 directional coupler into a 50ohm dummy load. The SA will take a feed from this. So, I will have 40dB attenuation up front.

I was originally intending to use the exciter at 1W but must plan for a 3W cock-up. The directional coupler has a mid-range limit of 2W so 20dB before it would drop the 3W to 30mW or 15dBm. The SA quotes a maximum input of 20dBm (with the internal attenuator set to 30dB). So, I think this means the mixer can handle -10dBm max.

My thinking is the directional coupler has an attenuation of 20dB which takes the worst-case signal down to -4dBm. Not low enough. Adding another 6dB attenuator would guarantee that running the exciter at high power and if I forget to check the internal attenuator is set above 0dBm I will still be safe.

Is this being over cautious? If I use 3watt and attenuate, then I cannot accidently triple the power. I have lusted after having a spectrum analyser for decades and making the magic smoke is something I really want to avoid.