For instance you can use a generator with an impedance of 75 ohm to drive a 50 ohm line, allowing for the additional 1.94dB drop (a 60% drop versus the matched case of a 50% drop).
If you're using non standard load, you can easily recalculate amplitude when you know 50 Ohm load based amplitude. With HiZ you will stuck, because there is no actual HiZ in reality. There is always some impedance on the output connector. Even if you BNC is open it still have some impedance, which depends on the frequency. HiZ doesn't exists in reality, so this "HiZ" amplitude is not "HiZ", it is acutally amplitude for some high random impedance. And this is why these "HiZ" volts are random.
The fancy and more expensive signal generators may well offer such a feature. Considering your question, they probably do and possibly by monitoring the current versus voltage output to calculate the actual impedance it is connected to so as to leave the operator a hand free to scratch their balls.
All that is required is an additional input from a current sensor to be able to calculate the load impedance and the resulting voltage.
There is no need to "monitor the current versus voltage output". No need for sensors. If signal generator has 50 Ohm output impedance, it will automatically keep "current versus voltage". The same as simple resistor doesn't need any kind of sensors and "monitor the current versus voltage" in order to keep it's resistance properly. This is simple Ohms law!
I = U/R
There is no need to monitor for current and voltage, the current will be automatically adjusted to the voltage, according to the Ohm's law. And you can simply add your load impedance and get current correction. Since almost all RF equipment has 50 Ohm connectors, you're don't needs to think about it, just use standard 50-ohm impedance voltage.
You can easy calculate dBm power value from 50 Ohm voltage. For HiZ it even doesn't have sense, just because you cannot measure power on random HiZ impedance.
This will turns into problem if you're using so called "HiZ amplitude". In such case it will turns into:
I = U / [random high impedance]
If you will try to convert it to dBm power, it leads to:
P = U^2 / [random high impedance] = [random power value dBm]
This is why HiZ amplitude in context of signal generator for MHz frequencies
is complete bullshit.
Personally speaking, I'm rather glad that the Chinese designers of cheap affordable T&M kit have avoided this insult to the intelligence of their hobbyist target market demographic by not adding such unnecessary "Bells and Whistles"
Actually these Chinese guys added "Bells and Whistles", such as useless "HiZ amplitude". It makes hard to use this signal generator, because you're always needs to recalculate real amplitude to these random volts and it needs to re-check real amplitude with measurement equipment in order to avoid confuse.
But you didn't answer on my question - is it possible to recalibrate FY6600 in such way? To show standard 50 Ohm amplitude. It will make life more easy. I hear that there is possible amplitude calibration. So, may be it can be done with proper amplitude calibration for standard 50 Ohm load?
Just think about some special multimeter which show non standard voltage for "spherical horse in the vacuum" model. And you're needs to multiply it's result by sqrt(35) in order to get standard voltage. It's just awful. The same thing with this "HiZ amplitude". This is how this "feature" looks like from the user's point of view.
I remember that some people mention that there is some attenuator in the FY6600 frontend, which unfortunately didn't properly matched to 50 Ohm due to poor design, so it may leads to issues with 50 Ohm voltage calibration. Is this true?
Why developers of FY6600 are trying to make life difficult by inventing this random "HiZ amplitude" instead of using standard 50 Ohm voltage which is used everywhere? Is this just attempt to hide some critical fail in hardware design?
I just don't understand - why?