The 438A does not provide a way to store a cal factor and corresponding frequency for recall at a later time - This also means that it won't do the cal factor estimation for frequencies between cal factor points.
That was one of the reasons that I kept my 437 until I was able to move to an E4418B - I keep a 438A around for those times when I need a dual channel and just live with the need to enter the factors when measuring.
TonyG
