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Comment by gffrd | Hacker News Reader

The other day, I was taking a call on my iPhone, over the earpiece, in my office suite's lobby.

The connection was rock solid, and then out of nowhere the audio just disappeared, without warning … but the call didn't drop. A few seconds later it returned. The person on the other end said they heard what sounded like a child for a second. I was perplexed.

Fast forward a week, and this happens again. I look at the call screen, and notice that the audio is being routed to Bluetooth? Opening it, it says I'm connected to my car. Not possible: I'm here, in my office, took a bus in.

I look up, baffled, and happen to see my wife drive by, 40 feet away, through a concrete wall and some glass.

Damn you, auto-connect. DAMN YOU.

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I really want an option like this

   Enable

   [ X ] Audio

   [   ] Phone Calls

   < Pair >    < Cancel >

Because I never, not one single time, wanted a phone call to blast over my car audio. Not once.

I can't be the only one that has wanted the car to be a speakerphone exactly 0 times.

Heck maybe someone is the opposite. They love terrestrial radio or their CD collection and also the speakerphone feature. Give people options.

Is this not a thing? My phone has the option to disable phone calls but leave audio enabled. Also my car now asks before transferring a call in progress from the phone to the car instead of doing it automatically when it's in range.

Oh it is! It might be new. It's yet another reminder to constantly recheck things and not assume things don't change

I wonder if it works. Thanks. I'll try it!

So now I remember.

The car refuses to connect unless I give it phone permissions.

You can do this on android for quite a while on a per decive level. Not sure if that's what you use

I don't think my iPhone has this, but my 2018 Škoda has this. There are exactly these two checkboxes, they say something like "phone" and "audio" and they do exactly that. And this isn't even when pairing, you can bring up the menu anytime and just enable or disable each functionality. I usually drive, so we connect my girlfriend's phone to "audio" so she can be the DJ while I leave my phone connected to "phone" so I can take calls.

(My car as a speakerphone works beautifully. It's not even about the speakerphone, more about the good microphone, the ability to call someone, adjust the volume and then hang up without having to take your hands off the wheel.)

Also the case on my 2014 Citroën.

And in my 2020 BMW - assuming I don't use CarPlay.

Same in my 9 year old BMW, I can connect audio, phone, or both.

I drove a rental BMW a few weeks ago, and I think it had exactly this setting. Don't know if it does what you mention here.

This is an option in Android.

Settings > Connected devices

Tap on the device, that brings up a list of switches for features the device is allowed to use.

I assume iOS probably has something similar.

You are unfortunately assuming incorrectly.

Bluetooth on iOS is a mess. If you are paired but not connected to a device, all you can do is forget it.

If you are paired and connected, you can:

* Change the name of the device as it appears on your phone

* If it's an audio device change its function (for example "car stereo", so iPhone will not automatically decrease volume if you put the volume to max which it will do for "headphones", as you probably control volume from the car stereo itself)

* Disconnect

* Forget

That's it.

The audio preference to be bluetooth audio only can be configured in the cars bluetooth connection settings, usually.

All Android phones have exactly that selection when connecting to a BT speaker. It explicitly says if you're connected for audio and/or speech and you can set your preferences.

Why wouldn't you want that? Do you not take calls in your car?

I consider calls private and it makes me uncomfortable

And it's funny how quite a few times people don't realise how their conversation is perfectly audible (and even quite intelligible) outside of the vehicle due to some combination of either bad soundproofing/speaker placement and/or excessive interior volume levels.

My phone connection is screwed up in my 2012 Honda Civic so all the caller hears is a high pitched screeching sound. I have not found a way to turn off calls on the Honda system or on my iPhone and it's so frustrating! Especially when calling out because you can't switch to using the phone's speakers/mic until the call has been answered. This means there is always a 10-20 second bit of time where I have to shout my apologies until I can get it changed. Or I have to turn bluetooth off entirely and it takes a minute to get it connected again after my phone call.

Every Toyota I’ve driven has this option. I agree, it’s quite nice.

Toyotas used to have that option.

I actually take calls over car audio frequently. But only when I am inside the car, obviously. When car's Bluetooth tries to take over from the garage while I'm inside the house, that's hugely annoying.

This is why I hate that modern flagship phones usually don't have a headphone jack.

Once you pair devices, it defaults to this connection.

My SO often borrows my noise-canceling headphones and as it stands they're firmly paired with her iPad and will not let go without elaborate ceremony.

I had a similar problem borrowing my wife's NC headphones. Months later I discovered Sennheiser BTD 600 which is basically an audio-only BT dongle (so it shows up as a USB headset). Now whoever wants to use the headphones just plugs in the dongle (it has both USB-A and USB-C). Works without a fuss.

You are using them wrong. The intended solution is to buy another set of headphones.

> and happen to see my wife drive by, 40 feet away, through a concrete wall and some glass.

Is she okay?

Ironically, perhaps, the car everyone must be complaining about in this thread introduced call transfer controls that avoids just this. Through an OTA update.

Yes, it's Tesla.

If you're already on a call when the car connects to the phone, you must press an on screen button to transfer the call to the car audio.

(Bloody brilliant, if you ask me; and also something that couldn't be introduced to existing cars post release that were buttons only. I was quite anti-screen before I got mine, but now that I've gotten firmly used to it - and seeing enhancements every few months, I'm quite happy. I would like more generic mappable buttons on the steering wheel, but it's not a deal breaker).

I was sort of in the anti-touchscreen camp too, but the early 2020 Tesla has just the right controls on the wheel and stocks that I don’t mind the screen. And, also, the big screen for maps and backup cameras is really nice.

Well the anti touch screen camp is more accurately a "don't take my dials and buttons" camp

This is really it for me. I don't mind having a touch screen; I just want to never have to use it while I'm driving.

I'd call it more don't make what was one press of a button into five taps on a touch screen.

Plus gloves in winter regions we wear gloves 6 months of the year.

The automatic (#1) steering wheel heater would help you with that, it's the one feature I didn't know how much I needed. And that's just from Melbourne, Aus, where it gets down to about -1c to 2-3c (30-37f) at the most. :-)

I don't find myself needing to dig into any menus whilst driving. I use voice control to change music etc, and I tend to enter my nav at the beginning of my trips. You can still control volume and pause with steering wheel buttons. I'd like call answering and hang-up buttons as well for the steering wheel.

As a Fanatec Podium owner/sim-racer I'm used to having more physical buttons and there's definitely room for more underneath + on the back. I would like some for immediately folding mirrors and a few other functions.

#1) Automation of steering wheel warmer was a recent OTA; previously it was manual.

The problem though is that it's a Tesla. An OTA update won't fix that.

Is there some improved BT technology out there? I’ve seldom seen it go more than 20 ft or through a substantial wall.

Wikipedia says this about Bluetooth:

> In the most widely used mode, transmission power is limited to 2.5 milliwatts, giving it a very short range of up to 10 metres (33 ft).

But that's not really how radiation works. You can transmit more by using more power, sure. The louder you shout, the easier it is for people to hear you.

You can also receive more by having a bigger antenna. The harder you listen, the more you can hear, regardless of limits on source volume.

So the easiest way to explain this would be to guess that the cars are using bigger Bluetooth antennae than usual.

Antennas are not amplifiers. As long as the antenna is correctly tuned to the impedance of the transmitter output stage, it will radiate most of the power of the transmitter, but cannot exceed 100% (it is a passive element, and exceeding 100% would break the laws of conservation of energy). In this case the size of the antenna does not affect the total power emitted and there will be no range gains from using a bigger antenna.

What the antenna size/shape can affect is the directionality of the beam. By emitting the same power directionally, you can increase the range in some directions at the expense of reducing the range in all other directions. But the total power would be still the same.

Also the reception gain is actually the same thing as emission gain. You cannot make a passive antenna that has better reception without making it more directional, which means worse reception from some other directions. You cannot improve reception from all directions by making a bigger antenna.

Bigger antennas can positively pick up more signal. The Mars rovers do not have megawatt radio transmitters, instead we use enormous antennas on Earth.

We use antennas which are incredibly directional for Mars rovers. Compare a regular lightbulb vs a flashlight with a lens. Total light emitted might not be that different, but the intensity at the same distance (or how far the light reaches) is because the beam is focused. That works the same with receiving signal: a giant dish will focus the signal to a central point, and a Yagi-Uda antenna will use a similar phenomenom to focus the signal on a dipole.

Ofcourse car bluetooth presumably has an antenna that radiates roughly sphere-like, it wouldn’t make sense to pick up signals on the right of the car with a dish or something.

To that end, bigger antenna doesn’t do a whole lot to boost signal. There might be other factors at play increasing the reception though, such as signal polarity and whether the length of the antenna matches the frequency in a correct way (or is some multiplier of it). For Bluetooth that’d be roughly 13cm or 6.5 or so.

> a giant dish

So why don't we just use a small dish?

Because it wouldn't be as directional as a big dish. The relative size of the dish vs wavelength plays a factor here. If you make a dish thats the size of the wavelength it wouldn't even work as a dish, it would receive the signal from all angles. This is also why high gain antennas for higher frequencies can be much smaller than for e.g long waves.

It works two ways: one is that you can go lower in frequency (e.g. bigger wavelength) if your dish is bigger, the other is that you just capture more of the signal. If you take light as a metaphor, a bigger lens will just provide more 'signal' at the focal point.

Of course a bigger antenna can pick up more power. Just imagine placing two antennas instead of one. Each one receives a certain amount of power. Two will receive the sum of that power.

That doesn't work that way. If you sum the signals from two antennas, those signals would differ in phase depending on the direction of the incoming wave. For some directions they will add up, for others they will cancel out. That would change the directionality of such antenna system, which is exactly what I have written above - you gain somewhere, but lose elsewhere. Antenna gain is a function of only its directionality. A theoretical, ideally symmetric antenna has gain 0 dBi, regardless of its size.

If the antennas cancel, you change the polarity of one of the antennas and then they add up.

But then it is no longer a passive element. Sure, you can use N antennas connected to some electronics that adjust the phases dynamically so they always add up. This is what modern "beam-forming" wifi routers do these days to improve range.

Bluetooth from an regulations point of view has the same power limits as wifi (it's in the same 2.4 Ghz ISM band). In practice Bluetooth devices are small which limits both antenna size and desired power consumption so they tend to operate at a shorter range. If one end is a car, which has none of these limits, and the other end is a phone with a reasonably well designed antenna, you can get decent range.

I turn my bluetooth completely off for this reason. It's the only way I can figure to prevent this.

The only way to win is not to play.

I'm not sure if this is even possible on my car. Is there a hardware module I can remove?

I turn it off on my phone. Don't know if there's a setting in the car. I'm sure you can rip out some Bluetooth receiver in the car if you're really determined

And mine won't even hold a steady connection from a few feet away! Not without having to "turn it off - and turn it on again", at least once every few days.

Is this due to car or iPhone option?

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