HI,
I have an SR505n with an older firmware built in 2013. That fw enabled transmission in both 2.4Ghz and 5Ghz bands, although it was not configurable.
However, I updated to fw version 2.6.x.x and the router no longer transmits in 5Ghz - it appears that it has been disabled.
If there are solutions or workarounds to this, I would like to know.
Thanks