I've been a ham and shortwave radio listener since childhood, and recently picked up a Tecsun PL390 pocket radio, based on the Si4734 digitally-tuned counterpart to this chip. Its performance is impressive, especially for the price.
In both the Si474x and Si484x devices tuning is kHz-stepped, not continuous or fine-stepped. At first I was disappointed, familiar as I am with classic continuous analog tuning in shortwave radios. Their Si57x oscillator has very fine tuning.
But the PL390 has an Easy Tuning Method (ETM) which scans the entire HF spectrum, memorizing the frequencies with any signal at all. Then the tuning dial selects these frequencies only. I like it now that I'm used to it. The Si4734 is sensitive enough that ETM gets the weakest stations. It's an interesting alternative way to listen to a radio, certainly easier for the average person.
If you're at all interested in these chips, you should try a Tecsun PL390.
Good concept with the exception that AM band despite additional filtering, it is still susceptible to weather (for reach), and natural noise (lighting and other RF sources (engine sparks, electric motors, etc ).
So that leaves FM as a cleaner option, if the stability can be adjusted and corrected with weather (environment temp), it is a nice low-cost solution, and beats the monthly-fee base satelite radio.
The IC can tune to MW/SW/FM bands with 2 to 3 volts their respective tuning coils connected.It needs a crystal and 2 capaciors connected externally. The stereo audio out put to be amplified for connecting the loud speakers. The IF selectivity shown is good. I just recall my first crystal radio receiver using one Ge OA79 diode antenna coil and variable capacitor and a wire antenna in the year 1968.
Interesting article. The questions I had, while reading it, are (1) how are FM radios built into cell phones different from this (aside from the display, which I consider to be a tangential device), and more importantly, (2) why haven't all radio chips these days incorporated digital IBOC/HD Radio/Ibiquity, call it what you will? Or perhaps even the Euro DAB system?
I have a wonderful Sangean HD Radio AM/FM band tuner connected to my stereo. One of the very few such stereo tuners available. Why should HD Radio be such a rarity? It's great, it supports a lot of extra programming, there's no silly monthly fee involved, it could make the AM band useful again, as opposed to hopeless, and the chips are very cheap now. Every radio should incorporate one.
Si484x has the flexibility to adjust the stereo/mono blend criteria--the criteria can be set to mono in weak signal areas. I also understand other Silabs products like Si47xx also have this flexibility for memory push buttons application.
My first radio cost £6 10s 6d, probably $150 in today's money. It had six transistors: RF oscillator/superhet mixer, two IF amplifiers, a diode detector followed by a phase splitter and push-pull amplifier driving the LS transformer.
The one thing wrong was that it had wheel tuning so you couldn't flip between stations.
My faithful Sony ICF-M750L 'wireless' has memory pushbuttons which work just fine, but it has a vicious synthesized 9Khz filter/tuner that prevents you detuning it a lttle to boost the audio HF; oh, and on FM you can't kill the stereo in weak signals areas, it just keeps on trying, with unlistenable results. Win some, lose some, eh?
(No, we can't get DAB reliably here).
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