MacPorts believes something in the dependency chain of gqrx requires gnuradio to be installed universal. It's not installed universal on your system, so MacPorts is trying to rebuild it universal. To do that, it has to first rebuild gnuradio's dependencies universal. One of gnuradio's dependencies is py27-scipy, and it does not have a universal variant (#19397), so it cannot be built universal, so the operation fails.
I don't yet know why MacPorts believes the universal variant is required here. Typically that happens on 64-bit systems when one of the ports declares that it requires a 32-bit build using the line supported_archs i386 ppc but I don't see that line in gqrx or any of the ports it depends on.
