S21 VNA Connector & Cable Loss?
If I run an S21, will the results be across a frequency span like an S11?


Yes, for most devices the insertion loss (\$S_{21}\$) varies with frequency, so you should measure it across the whole frequency band where you would be using the device.

You'd usually use the same menus on your VNA to set the frequency range and number of steps for an \$S_{21}\$ measurement as for an \$S_{11}\$ measurement. In fact, for the best accuracy, the VNA will probably measure all 4 S-parameters at each frequency, because the \$S_{11}\$, \$S_{22}\$, and \$S_{12}\$ measurements will contribute to correcting the \$S_{21}\$ measurement for test set and cabling effects.

In comments you said,


  I'm just wondering if the S21 is swept across the frequency bands so I"ll get a table of correction factors or if you can just generalize the number.


For best accuracy, you would want a table of correction factors.