My questions are as follows:
1. Is the internal inductor VCO really the better phase noise in the 440 to 458 MHz range? If so, why?
2. Why doesn't the wideband closed loop synthesizer suppress this behavior at 10 kHz offset? With a 100 kHz typical bandwidth, noise should be suppressed down to the level of the divider and multiplied crystal noise at 10 kHz, for either VCO form.
3. Is the input protection on the VCOin pin relative to 2.3V or to the chip supply? If it can be raised above 2.3V externally, it would eliminate the significant design weakness of limiting frequency range by such a limited steering voltage.
4. In a related note most pertinent to the "V", might a future version allow a larger charge pump voltage that is more typically needed by VCO modules, and also the option of programming the charge pump polarity? When raising the steering voltage with an active loop filter, an inverting active loop filter is lower noise than non-inverting. But, it requires inverting the charge pump polarity, which is a feature found on almost every synthesizer.