Yes this has been addressed before. But it is worth going through an example of where the number might come from. Note that I do not work for Ettus. I have Ettus radios on my bench here. (And like them a whole lot.) I am not advocating for a different limit in the datasheet. However, I encourage my fellow Ettus users to look at the schematics. There's a lot to be learned from them.
The B2xx has a lineup between the antenna input and the first really sensitive part that looks like this: ANT ---> Switch ---> Switch --> Balun --> expensive A/D with integrated preamp According to their datasheets, the two switches are practially bullet-proof. The absolute maximum rated input power is about a watt for both of them. The Balun is similarly robust, with an absolute maximum rating of about 2 watts. But the AD9361 has lots of magic smoke inside that is just waiting to be liberated. That chip as an absolute max rating of just 2.5 dBm. The Ettus knowledge base webpage at https://kb.ettus.com/B200/B210/B200mini/B205mini#Input_Power_Levels indicates that the max input power is 0dBm. Why wouldn't they say 2.5dBm? I can only surmise, but I've been an engineer for a long time and I'd never tell a customer to push it to the limit. The risk is that the customer will wreck something that I'll have to replace or repair, or risk disappointing a customer. The prudent and responsible thing to do is to allow a little margin between the system absolute maximum rating and the component absolute maximum rating. (And yes, I know I ignored the losses through the switches... but that only gives a little more margin. A good thing.) ----------------------- Additionally, be careful about path loss assumptions for antennas that are close to each other. Proximity may mean that the two antennas are in each other's near fields. Strange things happen in that region. Wave fronts aren't planar. Sources are distributed. Apertures are not what you think they are. ---------------------------- I hope this is helpful. 73, matt
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