I have replaced bad samplers in the past (on HP8753ES instruments).? And yes, when you replace a sampler or a port coupler you do have to run through a calibration proceedure to get everything just right.? The calibration proceedure isn't very intense and can be run in about 30 minutes, but it does require a few insturments (power meters, special cables, etc) to do it.? The power meter requirements vary depending on whether you have a 0-3 GHz or the 6 GHz option, but that might be only on "D" and up that you have to worry about this.
But if you fail to do the calibration then all that really happens is that your baseline response prior to doing a cal is a bit off.? Once you run through a normal 50 ohm cal (which of course you would do prior to any measurement), you are going to get pretty decent results.? So, long story short if you can do the recalibration, great - that's recommended.? If you can't, not ideal, but as long as you do a proper cal prior to making measurements you should be fine.
Depending on where you are at,? one of us might be able to loan you the equiptment needed to do a cal.? It's really not that extensive.
