I am working on a deal to upgrade my 8753C with 84074A 6 GHz test set to an 8753E. I need to decide whether to keep the existing test set and get an option 011 analyzer, or get a unit with the integrated test set.
From looking at a comparison table I found, it appears that the integrated test set offers 10 dB greater dynamic range below 3 GHz (110 vs 100) but 10 dB worse above 3 GHz (100 vs 110). I'm curious why that would be and whether it's a real difference difference vs. conservative specs.
Another factor is that the E goes down to 30 kHz, which would sometimes be useful for me. The 84074A test set is only rated to 300 kHz, but I don't know if that's because at the time it was made the analyzer didn't go lower. Would the test set work down to 30 kHz with the E analyzer?
The deal I'm working on makes it cheaper for me to get the option 011 unit and keep my test set, but I want to know if I'm really giving up anything by doing so.
Thanks!
John
It's been a while (I designed in the 85047A in 1986), but I think the difference is the external test set uses a bridge/coupler for the reference channel tap, where the integrated uses a 2 resistor splitter, so it has a bit lower source power and a bit lower dynamic range. The low end performance should be similar but I think the DC blocking capacitor might be a bit larger in the integrated version so the low-end rolloff starts a little lower. The integrated version actually works to 10 kHz but is spec'd to 30 kHz. The 85047A was designed before the 8753D added the low-band path, and so was never specified/tested below 300 kHz but should operate fine to 30 kHz (with a corner freq of about 120 kHz), with 18 dB of additional degradation in dynamic range.
The worse dynamic range in the high band path (3-6 GHz) is because the test set has an internal doubler to get the signal up to 3 GHz. In the internal test set, instead the YIG oscillator is routed (through a set of filters and amplifiers) to the output directly, and so you get much more output power at 6 GHz then in the test-set version. I believe if you get a 6 GHZ version of the 8753E then the doubler is bypassed and you still get good power, but the 3 GHz requires the doubler to get up to 6.