You need a car kit plus an external antenna; the car kit to hold your cellphone, the antenna to establish and maintain a correct high-frequent connection to the base stations. A car is a Faraday cage, cellphones without connection to an external antenna and radiating wildly inside your car will only serve you if a base station is very near.
1 The problem with mobile (in-car) phoningIf you are not happy with the airlink quality of your cellphone while you drive, you've come to the right place. Just forget what they've told you so far, most of it will have been wrong anyway: Most don't know what they're talking about, but there also are others who just don't want you to understand the issue, therefore keep on trolling to confuse you. Just keep reading with an open mind.
First of all, I cannot promise you an immediate solution to the problem, because it is a bit complex, and some of its factors are hard to influence for users. But I can explain you in simple terms what is going on, and what you would need in order to obtain, plus maintain, decent operational conditions, and which of the factors you yourself can influence, and where you can (and should) demand changes. After having read the text on this site, you will be in a position to judge for yourself, so you will no longer be dependent on advice from cellphone chain stores - let alone network hotlines or similar 'experts'.
The first requirement for decent cell coverage is something your network operator will have to provide - a sufficient amount of base stations (this is the centre point of the radio cells). They can be miles apart (don't be fooled, this is a metric site...), depending on the terrain (which can also be artificial, like buildings): With flat terrain, fewer base stations are needed than in mountainous terrain (or some built-up areas), so the base station's signal can reach your phone (downlink), and - even more important - your phone's signal can reach the base station (uplink).
The important thing is that the signal footprints emitted by the base stations overlap at their edges with the neighbouring base station, because only that way can you expect a smooth handover from one cell to the next while you move. If there isn't any base station because the network operator didn't wish to set up one just for you (in some isolated area), then you're out of luck - keep going until the next one comes up. (In an emergency, you can go back where you had coverage, or you try and reach higher ground and/or possibly unobstructed visibility, in order to re-connect and call the emergency physician.)
And the footprint just mentioned is based on the downlink as measured near the ground with a correct antenna. If you want to take advantage of this same range while driving in your car, you will inevitably also need a correct antenna, which must be an external antenna, because your car is kind of a Faraday cage. Makes sense, doesn't it? Because otherwise, you just pollute your car with your phone's wild, unorganised radiation, of which just a fraction will reach the base station. Ever listened to someone driving and talking to you, while sounding wailing, distorted, synthetic, almost supernatural - or simply cut off? That's because he was too far away from the base station and didn't have an external antenna.
You don't believe me, huh? Well let's see what a well-known cellphone operator has to say about you and your cellphone in your car - or in his own words, how to 'get the best mobile signal in one's car' (= downlink; and I should add, most of all, out of it = uplink, because this is even more critical: The way the base station hears your phone is the way your correspondent will hear you). For full size, click here. NB: Please note my comments after his advice:
Did you see? He offers you 3 options. He more or less discards the red and yellow option, instead recommends the one marked in green colour: 'Being connected to an external antenna provides the best signal performance when using your mobile in a car. Using products like the Bury System 9 cradle will enable you to secure and charge your mobile as well as providing a connection to an external antenna': Right. A little more about it in a moment. NB: I'm NOT a Bury sales agent. There are also other makers.
Then he goes on to say - and this needs an explanation, because it can be missunderstood in several ways: 'It is important to note that external antennas are network specific and will not transfer across different mobile operator networks': Network-specific? Does he mean to say it may work fine on his own network but not on the one run by a competitor, or what? Whichever way, we simply can't let it stand that way.
What he probably was alluding to was the fact - if we limit ourselves here to the world-dominating GSM standard and its subsequent further developments - that there are a number of frequency bands in use. The most usual ones are 900 and 1800 MHz on the 4 non-american continents, plus 850 and 1900 MHz in most of the Americas (the countries that haven't followed the american frequency plan there, like fx Venezuela, use again 900 and 1800 MHz).
Now just as you can get quadband phones that cover 850, 900, 1800 and 1900 MHz, thus are real 'world phones', there are external antennas that cover these same bands. Just make sure you get one of them, and forget about this mystery remark about 'network-specific antennas'.
Antenna-wise, it gets a bit more complicated if you include 3G, which is important for faster data transmission, not to mention more recent developments like 4G etc, because they have been moved higher up in the frquency band - so normally above 2 GHz (which equals 2'000 MHz). If your antenna is specified to reach up until 2 GHz, then it will attenuate the frquencies above that limit - the further up they are, the more attenuation you will get. Just as the phone industry tried - so far successfully - to keep up with the extended frequency bands, so the antenna industry probably will, provided there are enough potential customers to justify their investment.
PS to american readers: Did you realise that there was no mentioning of a 'booster'?! Boosters are proverbial snake oil. All it takes is a technically correct external antenna, then the radio energy will be transmitted into/out of the car at an efficiency rate of near 100 % (galvanic coupling assumed). Ask any qualified, non-corrupted radio technician, although they may be hard to find these days. Without an antenna, you will most of the time pollute the interior of your car with the phone's electromagnetic waves (unless a base station happens to be in front of you), instead of getting your signal to the base station.
ACMA, the Australian Communications and Media Authority, says virtually the same as I do - only that they actually prohibit the use of boosters. The origial link has changed, therefore you'll find the text here: page 1 and 2. And of course, also they recommend the use of a car kit and an external antenna:
Also, leading german antenna maker Kathrein (pronounced CUT-rhine) says the same thing:
This is a screenshot of page 13 of their document Basic antenna principles for mobile communications, written by Peter Scholz, dipl-ing (comparable to MS) at Kathrein.
If you even at this stage have not managed to comprehend that an external antenna is not for geeks but for everyone using a mobile phone inside a car, you will probably not get there in the foreseeable future. To save you from wasting more of your precious time, let me offer you this emergency exit.
2 The car-kit solution presently availableYou will remember that the network operator recommended to get a car kit and an external antenna.
Generally speaking, unless you have above-average technical insight, I would recommend that you first try to get assistance through a qualified 2-way radio dealer (that's probably not a CB radio dealer, although you could try) who has a workshop. In Europe, this was easily possible, but since about 2003, everything has changed, and almost over night - it looks like a political decision posing as an economic decision: Earlier, we had 2-way radio workshops where we bought mobile phones, plus car kits and external antennas; they would also mount them. In conformity with the american 'model', we are having today phone chain stores manned by 'children' selling us 'smartphones' to be glued to the windshield; for problems, there are 'hotlines'. Is the american model better than the classical european formula that it deserved to replace it? There are few such dealers left only, and the real professionals seem to deal with the government only, or large businesses - see both 2-way radio antennas on the roof of this swiss fire brigade vehicle:
Surprisingly (?) enough, also american police seem to be utterly intererested in having correct 2-way communication antennas, as can be seen on this photo:
So the pattern seems to be: 'They' are allowed, and you are not supposed to have it. although it's NOT 'forbidden' - KEEP THIS IN MIND.
Would you get something professional like that?! You don't really get an explanation for the changed situation, you'll just get ushered out, more or less politely. Keep on trying there, your cellphone chain store is as useless as the network operator's hotline. What you want is *not illegal*. Why should he refuse to do business with you?
Regarding the antenna, I suggest you try to browse your local market to see what you can get. Like I said, it should at least cover 850 to 1900 MHz, and the further up beyond 2 GHz (= 2'000 MHz) it reaches, the better, with regard to 3G, 4G etc. Go for a roof antenna, or for an on-glass antenna (downside: a little loss there compared to a roof antenna, upside: no hole needed) which will be stuck near the roof's edge, for best performance.
Regarding the car kit, the network operator gave you the name of one of the major makers - Bury [pronounced BOO-ree]. What he did not tell you was, in theory at least, that the antenna can be coupled to the phone either through plug and socket (galvanic coupling), or through '2 antenna wire loops on top of each other' (one in the phone, the other in the cradle/phone holder - inductive coupling). The first version gives you a transmission efficiency of near 100 %, while the second somewhere near 70 %. Then you'll have the first, thank you - right? Wrong: They used to be available, until about 2003, in Europe and closer related countries like Australia or New Zealand - then they disappeared, over night. So as long as no phone makers are willing to equip at least their upmarket phones with all the contacts necessary to operate a professional car kit, so car-kit makers can adapt their products accordingly, you will have to go for second-best, thus inductive coupling - but this is still much, much better than no external antenna at all.
In #4 (below) you can see how I solved the antenna and car-kit problems, for the time being. I also replaced the toy-like smartphone (which is a euphemistic term to express that you get a computer and cellphone in one, like it or not) by a tool-like laptop-over-cellphone formula (so I kept computer and phone separate also on the road, just as you do at home), but if you're so in love with your smartphone, then you can certainly ignore that part of the reconstruction.
3 The car-kit solution we're waiting for to re-appearLike I said: We had it all before, until it mysteriously disappeared, and without asking our consent first. You don't believe me? Look here, and focus on the antenna contacts (inside the cradles, top left in the 1st photo, top right in the 2nd):
Why did this all disappear? Let it suffice to say that since that time, America and its smartphones (this includes asian makers, who traditionally follow the alleged 'requirements' of the american market), plus the ensuing never-ending, breathless 'new model' hype - which doesn't let you come to your senses, so that you just hustle along like a lemming - have dominated the global market. There is no space for national (european) 'special ways', no matter how technically perfect they are - quite on the contrary. Everything has to submit without contradiction to the debased american economical logic - which struck us about 1998 for the first time and in a negative sense, when they introduced their 'hotlines' in our countries. Yankee business - so to speak. Around the same time, bulk importation of incompatible mohammedans started as well as total surveillance, including intimidation attempts through helicopter fly-pasts...
Another conspicuous thing is that one doesn't receive a reaction at all when addressing this issue towards expert media like Popular Science (editor-in-chief Kevin Gray). If one publishes it in forums, one finds oneself immediately under attack by the White House's propaganda trolls. Yes: Not only does the Kremlin have a troll factory to influence public opinion. Anything else would have been surprising.
Still I would like to have a complete, true and official explanation of what went on behind closed doors, that we one morning woke up to the disappearance of car kits offering galvanic antenna coupling. How could it happen that companies like Ericsson or Nokia simply trashed their superior professional car kits? And it also is a striking fact that such car kits were never on sale in America - americans made a real hard transition from correctly mounted, non-retractable carphones (connected to an external antenna!) to wildly radiating handheld phones glued to the windshield. Why is no-one with a high-frequency education there protesting? Why is there not one journalist to investigate, then publish the whole story? I already wrote to many of these so-called 'investigative journalists', but their silence is deafening. See here.
The next thing then would logically enough be to organise a kind of user pressure group in order to make the industry re-introduce professional car kits - the ones with a plug/socket connection to the external antenna. This is nothing where politicians should put their noses into, this is just between us, the users, and the industry. We don't want to see a professional communication system like GSM artificially dumbed down to some kind of 'CB radio 2.0', by having small yet essential accessories stealth-removed from the market.
PS: I happened to see that chinese maker ZTE partially seems to offer this formula again, however only to customers of Telstra (Australia). So if your purchase data are outside Australia (or New Zealand, it appears), they won't deliver. This is bad, because GSM is a global system, and you don't meet the expectations of a global system with a parochial terminal policy. And even if you were in a position to buy one such appliance there, you could then probably assume that it is SIM-locked, according to american logic. And again, we are being cheated by America, because everybody is blindly following the inappropriate diktats from there, instead of being aware of the european GSM spirit and developping their own concepts, based on it, instead of on american logic which continues to disimprove good things until they are f*kced up. Write to ZTE and tell them what you want to have!