I have got a working 8596E with options 012 (DECT source) and 105 and 112.
There appears to be no information about the specifications of option 012. However according to this article http://literature.cdn.keysight.com/litweb/pdf/5091-7761E.pdf
it is basically the tracking generator (option 010) which can be pulse modulated to generate DECT signals in 1.88-1.90GHz band. But it should also work as a regular TG (meaning 9KHz-2.9GHz). I can confirm what is inside the unit is indeed the regular TG and TG control board and LODA..., the whole TG kit. But in the software the amplitude is limited to maximum of -17.25dB which is OK for me.
Here is the problem: there is a hole in TG amplitude below 15-20MHz down to 9KHz. Basically its amplitude is flat and ok from 2.9GHz down to about 50-60MHz and it starts to decrease slowly and then it sharply drops at about 15MHz and goes 30-35dB lower than the set value down to 9KHz. It seems that there is a high pass filter in the signal path.
My question: is this the normal behavior of option 012 or there is something wrong and needs troubleshooting? If this is the normal behavior, can I modify it to become a regular TG 9khz-2.9GHz?