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Phones should have FM radio again
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this post was submitted on 02 Oct 2023
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You have an excellent point, and historically, yes, you did need something plugged into a headphone jack to facilitate the rx of the transmission, however, this isn't strictly required. Broadcast FM is in the 2-3m range, meaning a full-wavelength antenna would be aproximately 3m in length, we don't even see this on vehicles; most are limited to less than 1m. Even with aerial whip antennas for home-based hifi/stereo systems, often the antenna is not any longer than 1m/3ft, which is about 1/3rd as long as it should be for optimal signal.
The issue here isn't one of having the space for the antenna, since smaller antennas are used in all sorts of applications, such as with FM and vehicles/stereos etc. The issue is having enough antenna to produce a signal strong enough to differentiate from background noise. The signal to noise ratio is key here. Historically, the only good way to get more signal is to use a better tuned, larger antenna, or an array of the same, this isn't so much the case anymore. There's plenty of antenna designs that are still fairly omnidirectional, that can enhance signals. Combine that with more advanced filtering and pre-amplification, a large antenna is not generally a requirement anymore; even the 1m/3ft whips used on cars are often overkill for what we can do with signal processing and modern design. Look at any modern vehicle, and with few exceptions, there's no longer a visible antenna. That's not because there isn't an antenna for FM, it's because the technology has progressed enough to be able to use much smaller antennas to accomplish the same task. The antennas are still there, they're just so small and well placed that you don't need a flagpole on your hood or trunk lid to have it work as-well-as any other FMrx antenna.
Given that the proposal requires a minor redesign of the cellphones to incorporate the broadcast receiving radio, adding a small antenna, or simply using the chassis of the phone as an antenna, would not only be possible but it should be fairly trivial to accommodate for. by no means am I saying it would be the worlds greatest FM antenna system, most certainly it would not be, but it should be sufficient to differentiate the signal from the noise; with relatively trivial signal processing, it should be more than adequate for the purpose.
The technology surrounding FM broadcast radio didn't just cease and we get what we get; vehicles, among other specific technologies still utilize FM radios and development has continued on them even though very few people have been watching. The technology is far improved from what you can build with a battery, coil of wire, a speaker, and a handful of resistors/capacitors/etc. and similarly it's far improved from what vehicles had even 15 years ago. Add that to the fact that radio technology is all pretty much the same across the board (from what we use for broadcast FM, to WiFi, 4G/5G/LTE cellular, and GPS included), and a lot of the developments made in any area of radio can be almost directly translated to another radio on a different band, and there's a lot of technology that, unsurprisingly, will blow most of what most of us have in our houses on our hi-fi stereos, out of the water.
The wonderful thing is that a lot of it is tied to miniaturization and modernization of the technology, meaning a lot of this is tied into integrated circuits that are being mass produced already. IC designs that can be embedded into other ICs to decrease the overall number of chips in a device, fairly easily.
The point I'm dancing around is software-defined radios. SDR is becoming a huge player in all aspects of radio technology, and can replace far more advanced/complex systems with something less complex than a raspberry pi, and often less costly. The big cost of SDRs is mainly regarding transmission, since they don't put out a very strong signal, and need some significant and high-quality amplification to be useful; but we've seen SDR chipsets starting to dominate the lower-cost market within the HAM/Amateur radio space. Extremely capable, very small and power efficient radios, for significantly less cost than more traditional methods of doing the same. The issue is that first word: Software. With great software comes great responsibility.... or something. Fact is there's a lot of SDR radios out there with garbage software interfaces.... at least there are right now. Things are improving all the time. The wonderful thing about SDR, is that they're generally compatible with whatever you want to use them for... meaning AM/FM, or even something more elaborate like OFDM, or other modulation techniques. This means these radios can essentially be re-programmed on the fly to adapt to a new standard with little more than a software update.
I apologize for the long discussion on this, but the technology is so interesting to me the more you look at it. Yes, antennas are important, but not nearly as important as they were even 10-15 years ago.
Wavelength varies from 2.7 to 3.4 metres. Just because that is the size of the wave doesn't meant that a good antenna has to be that size. A very good basic antenna is a 1/4 wave vertical, and we see them pretty often as telescopic antennas on radios and cars. A 1/4 wave FM broadcast antenna will perform excellently, and will be 68cm to 85cm in length. More modern cars have antennas printed into a window similar to a demister strip. They are actually NOT smaller, some can be quite larve, but also very stealth. But the point remains is that they are NOT small as you suggest. Much shorter antennas exist, but there is a gain penalty, and that penalty gets more extreme the smaller the antenna gets. I have such a small antenna on my car and it IS an issue. In physics nothing is free, yes, you can make an antenna small and still have it be resonant, but you'll pay a price on effective gain.
This is a problem that technology has not solved. Sure, clever designs have helped a little, but there is always a price to pay if you try to cheat the physics.
A compromised antenna can work in a very very stong signal area, but it will easily be the difference between a clear solid recieve and no recieve at all in a fringe area.
AM Broadcast is an example of this, with antennas sometimes 2 inches / 50mm long or even less and hidden inside the radio. Buy as a ham myself with a HF setup, even my HF setup, which is a poor compromise on MF broadcast gets me stations from all over Australia. That isn't going to happen with a regular AM receiver.
Ultimately, sure you can have a mobile with no external antenna receive FM broadcast... but only in a VERY VERY strong signal area, within a few miles of the transmitter, while a propper antenna will work at 10x the distance.
This would work at very short distance only, it really would be that limited. Would it be useful for the people in those short distances? Maybe. Buy while a regular ordinary transistor radio with a telescopic antenna would work 10-30x further away, comparing those 2 really shows how much of a compromise is going on.
SDR's are not magic. In fact they actually have some drawbacks compared to conventional designs with regards dynamic rage, over loading etc.. Pulling the 'SDR' card and not knowing this i think shows your lack of understanding of the topic (not trying to diss, just an observation). SDR's are a great tool, i have 4 of them in front of me as i type this, so I'm no stranger. Icom IC-705, Icom IC-7300, HackRF and an RTL-SDR. You could also maybe count the University of Twente webSDR i have open in another tab, and an MMDVM at a stretch to make it 6. http://websdr.ewi.utwente.nl:8901/
This is all exciting stuff... but none of it has revolutionised RF physics for human portable commodity radios, nor even come close to an adjacent technology that could be adopted / adapted.
My ~ AUD$1900 IC-705 can go from picking up stations all over the state of Victoria, Australia with it's non optimal antenna tuned for 146MHz, to picking up literally nothing if i hook up a few hundred mm of wire to it's antenna socket on the bench here. And I can engage pass band filtering, up to 2 pre-amp stages, and a variety of Digital Signal Processing features and sill get... nothing.
I appreciate your passiona nd interest, but.... physics.
We can look at other technologies that are great... WiFi.. it's great, but the transmitter location is in your home and still struggles to cover some larger homes... from inside your home itself. Cellular.. again, great, but again, as the name implies it;s made up of 'cells', physics is a massive issue with cellular, each individual cell tower consists of tens or sometimes hundreds of transceivers, each connected to phased arrays of hundreds to thousands of antenna elements... and that's just a single site, many towns will need multiple of these for coverage. Cell is not immune to the limitations of physics, and it has to brute force the situation from the tower end so as we can have small devices in out pockets... and even with all that i get no coverage int he middle of my local supermarket. Do an image search for 'cell panel antenna inside' and see if you can find a picture fo the actual antenna elements, my results mostly got the rear so you might have to scroll a bit.
A lot of the modernisation you refer to is just that given the value we place on connectivity while remaining portable the effort has shifted to needing to bring the signals closer to the user. Looking at that broadly, while some gains have been made what's really happened is that the signal has been bought closer to you, making you think magic has happened.