When I run this program on my mac, it always recommends channel 52 for my 5ghz. That channel is not available on my RT3100 Asus router. Would it be advised to go to 149, or 48? I am not sure why it recommends 52, I think that is only a european channel.
Utilities like inssider are not the end all and be all of selecting a proper channel. I stopped using them for over a year now after I spent way too much time gathering the useless* info they provided.
Useless, because more often than not, the recommended channel was not the one to provide the best overall throughput, stability and consistency along with lowest latency for the network as a whole.
Instead of wasting your time (and do note that (possibly) testing with the utility running is giving a false reading for your networks speeds), test each channel one by one, reboot of all related networked equipment in between tests, and choose the one that gives the overall best performance.
As you have seen, inssider is a 'dumb' utility that takes nothing of the rest of your network into consideration. All it can do is give you the responses it has been programmed with.