I own a FPC-1500 and the lack of log-frequency scale is seriously frustrating for characterizing filters or using it as a VNA. I'm hoping I can write a script to pull the raw data and do my own plot on a log scale next time I have to. While we're ragging on this instrument,
1. I had to send mine back three times because it would whine about an IF stage overload in VNA mode, when everything was in its default settings and nothing was attached to the ports. On the third time, I guess they finally said eff it and sent me back a completely new unit.
2. 1 Hz RBW is horribly bugged - as in signals can vanish from the screen going from 3 Hz to 1 Hz. The solution from R&S was to downgrade the firmware, and a year after this was documented they have not posted an update.
3. The vertical scale adjustment is annoyingly limited. If I have an example -20 dB filter, I can't look at the narrow range of -20 dB to -30 dB using the full screen, unless I dial in 20 dB offset (which makes it appear like it is 0 dB filter, quite confusing for documenting work for later review).
4. Narrowing the frequency range blows away any S11 calibration or S21 normalization without warning. At least it could attempt to interpolate instead of making me disconnect all cables, bring out the O/S/L standards, and reconnect everything.
It's truly frustrating because this instrument is quite expensive in its class (just under $10k fully loaded sticker price - I got mine under a promo, but still a lot of cash) and is capable of excellent raw RF performance, but is hobbled by crappy firmware that as @PartialDischarge noted, they would be blasted for if this came a Chinese vendor.