After reading the white paper about designing radios using this chip, I AM REALLY NOT IMPRESSED AT ALL! Half of the paper was devoted to describing the alleged faults of "analog" radios, while the descriptions of how these ICs worked were sort of nebulous. It would appear that the target audience for the white paper is MBA types, similar to the pointy-haired boss seen in Dilbert strips.
In traditional radio solutions, the intermediate-frequency (IF) counter IC needs to interpret the local oscillator pulses as tuned frequency and translate these pulses to a display driver, which then displays the calculated tuned frequency. The Si484x directly provides its tuned frequency to the display driver via the I2C interface, thus avoiding any issues with the tuning disc misalignment, or counter errors etc…. leaving no room for error. The user hears precisely the station shown on the LCD/LED display.
This does seem like an interesting product, even more-so if the receiver tuning is continuous and not channelized. Channelizing immediately limits the applications to listening to standard broadcast transmissions, only a small part of the potential uses. While the method of non-channelized tuning is not clearly explained, it is certainly a valuable contribution.
Why in the world should there be any thought of putting a transmitter in a receive package? Who would be listening on broadcast frequencies that would be interested in doing anything? Besides all that, all that is needed to add a transmitting option is a connection to the local oscillator signal. Mix that signal with a modulated signal at the IF, and there is your transmit signal, ready to amplify.
I'm not getting why the displayed frequency would be that much different from the tuned frequency with a synthesizer or why the user would get frustrated. Here in the States, FM stations are on a 200 kHz = 0.2 MHz grid; I understand it may be a 100 kHz grid elsewhere. You tune to 107.9 MHz, for example, and you get KWVE; tune 1 click lower, and you get something else at 107.7 MHz. In both cases you see 107.9 or 107.7 on the display. Yes, the synthesizer may actually be tuned some Hz away from the displayed frequency to match the frequency of the transmitter, but the user doesn't see that, and he/she hears the desired station; what's the problem?
I like having this range of radio reception, but I would like to see an emergency radio transmitter included with the part. All you need is a low power FM or SW component to send out an SOS and your coordinates. It would not take much and it could easily save lives.