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I use 2G and 3G systems for my data logging projects. They are much cheaper. Eventually I am afraid I will need to use a full 4G LTE system (at least in the US).

You do not need to use a "full 4G LTE" system for data logging. Neither in the US, nor anywhere else. You WILL need to abandon 2G and 3G pretty much worldwide between 2020 and 2025, but do not need full 4G LTe for M2M communications (which includes data logging)

You can use LTE-M, a simpler variant of LTE, aproved in 2013 specificaly for M2M (like data logging) communications.

It goes easy on cost because of simpler modems and economies of scale because it is a pretty much single standard, and is very light on battery use (in line or even less than 2G, depending on Frequency Band, lower is better).

More info here:

https://www.radio-electronics....

But remember, we are now in 2018, there must be 5 years of advances in LTE-M2M communications, investigate further.

That's only one possible implementation, it doesn't have to be done that way but there is no money in it for the carriers if my phone can talk directly to your phone. http://www.radio-electronics.c... It can work without carriers, the carriers will want to control it by building authorization protocols into it so they can make money off of it.

LTE spectrum ranges from 850 mHz to 2500 mHz

No it doesn't. That would be MHz.

The frequencies you cite range from "roughly every 15 minutes" to "35 times a day".
The bitrates achievable at those frequencies are rather low...

In other words: YES, damned, case matters with SI prefixes.

I was just wondering this the other day...it seems to me that for a handset manufacturer it would make sense to put all of CDMA/TDMA/GSM/LTE/HSPA+ etc onto one chip, and define the frequencies and protocol by some BIOS settings. That way the same phone could be sold to every mobile carrier. I would think it should also be possible to include many antennae or fractal antennae.

Is this already going on? Or are handset manufacturers really putting different chips in the same handset destined for different carriers?

That's hard to do with the frequencies being significantly different. LTE spectrum ranges from 850 mHz to 2500 mHz - a wide spread to handle in a tiny radio. It's possible to do but then you have the annoying engineering tradeoffs of size, battery efficiency and cost.

I have heard stories of ham radio guys with cutting edge 1296 preamps and high gain mobile antennas blowing their preamps by driving down the street next to the airport full of hundred watt peak class 1090 MHz active transponders.

The 10 GHz LNA that I bought recently from DB6NT can't take more than 1 mW at its input. They specifically stress this point; a bad relay can blow the FET.

A common ham dish antenna for 10 GHz can have gain of about 30 dB. If two such dishes are pointed at each other and one transmits only 200 mW, the minimum safe distance between those dishes is:

FSPL (dB) = 20 log10 (d_in_km) + 20 log10 (f_in_MHz) + 32.44 -Gtx - Grx

Since we want to lose 23 dB (200 mW to 1 mW) the 'd' will be only 33.7 meters. Any closer and the amp burns up. This is actually well known in practice when hams show up with their microwave rigs and try them out in a parking lot. They are very careful to not point dishes to anything they don't want to cook :-) Many 10 GHz rigs run more than 200 mW; 3W is typical, but some do up to 10W (it just costs more.)

Radar operators also know to not point their radars at nearly objects. Some radars on civilian airplanes can't be ran on the ground - both due to radiation danger and due to the overload of the front end (burnination is optional but likely.)

Have a look at the info about LTE frequency assignments. OK, all you hams out there, how many MHz of the frequency band to carry a data rate of 21MHz at the various assigned frequencies? How much frequency spectrum is available? Divide X by Y and you get the number of simultaneous full-speed downloads.

Cell towers have phased antennas. This means there's a bunch of dipoles, usually in a circular arrangement. When a signal is received it can be angularly located by the relative phases of arrival at the dipoles. With a protocol incorporating chirping (a unit impulse convolved with a chirp system, then on receipt deconvolved to retrieve the pulse) the angle can be very precisely located. Once a transmitter is located the phased receiver can very accurately reject noise and other transmitters on the same frequency, based on their angle - in other words, if the phase(s) of the signal is wrong it's a reflection, echo, noise, artifact, or a different transmitter. This works so well that it can listen to a whole bunch of transmitters on the same frequency simultaneously by separation based on the transmission angle. The converse works as well; by aligning phases of the different antennas the transmission (virtual lobe) can be made highly directional (some will be out of phase to cancel, others in-phase for gain). In fact, the phase array can transmit to a whole bunch of receivers (stations) at the same time by simply adding up the signals for each antenna. So by using a bunch of phased antennas you create a large number of independent virtual narrow lobes of communication. As a mobile station moves around it's tracked and the lobe used to communicate with it changed as needed.

Finally, modern communications in the GHz band aren't based on FM modulated channels. They're time multiplexed. When a station transmits, it bursts for a few milliseconds. The rest of the time it's silent and other stations can use the frequency. In addition, there may be a channel arrangement, but in general collision domains can be self-managed by the stations while channel assignment requires centralized logic. But the biggest benefit is that the transmitter can output relatively high power (a few watts) during a brief period, vs relatively low power for longer periods. This improves range.

As a result of this, you can never get more bandwidth than that sustainable with a single virtual lobe. Your station will have a maximum power output (e.g. 3 mW/s, or in reality more like 3 W for 1ms); the better it can communicate with the tower the more packets it can send without exceeding its power limit. The same holds in the other direction, though it's limited by its single dipole receiver.

The real bottleneck that wireless carriers worry about is not their network. It's the capacity of a single cell tower to carry a finite number of simultaneous connections.

Have a look at the info about LTE frequency assignments. OK, all you hams out there, how many MHz of the frequency band to carry a data rate of 21MHz at the various assigned frequencies? How much frequency spectrum is available? Divide X by Y and you get the number of simultaneous full-speed downloads. Exceed that, and you have to start some sort of time-sharing scheme in which individual users grab a few milliseconds of exclusive ownership of each channel at a time. (Token Ring, anyone?)

Because of the way radio works, you can only get so much network bandwidth out of a particular frequency spectrum. You can do phasing tricks and subcarrier acrobatics to squeeze more out, but there will be a point at which you can't handle more devices per cell tower, no matter how much (wired/fiber) network there is behind it. And putting two cell phone towers right next to each other doesn't double the number of connections that can be handled; a phone connecting at 2410MHz to one cell phone tower will be putting out radio noise that a second tower right next to it will pick up. This is why AT&T is getting hammered in places like San Francisco and New York where there is a very high density of 3G users; they just can't add more cell towers. They're saturated; it's not because they're cheap bastards (they are), it's physics. That's how radio works.

Think of it this way: your FM radio has channels from 88.1MHz to 107.9MHz in 200KHz steps. Once all 101 channels are allocated, just "adding more towers" doesn't get you anything.

Smart phones differ from traditional cell phones in that they are "on the air" more than voice-only phones (insert teenage-girl joke here). A voice call might need 50kbit/sec for the duration of the call, and thus consume very little radio spectrum during that call (a handful of KHz). But a data session is a steady high-bitrate stream that can consume several MHz. Yes, interlacing occurs, but it really comes down to this: the limitation is how many MBits per second an allocated frequency spectrum can carry, divided by the number of simultaneous users of that frequency and their data demands. Once it's all in use, there ain't no more. Users get timesliced to slower and slower connections, until the granularity demanded by timeslicing and channel-juggling among X-thousand users of a single tower is so small that you can't even get a voice call through.

So yeah, I understand why wireless carriers would want to cap data usage. It sucks, but physics doesn't care how angry a consumer is, you can't sue to force 1000MHz of in-use spectrum to fit into 200MHz of allocated spectrum, and carriers can't throw money at physics until it goes away. Radio spectrum is a finite resource, data at a given rate requires a specific portion of that spectrum, and that's it. Something has to be capped. Data rate or data cap; something has to throttle usage, because there's not enough to go around for everyone to max it at once.

as I have seen you railing and railing on this over the whole thread, I decided to reply to this post. You obviously live in the same area I do, which is rather interesting, and you are posting on Slashdot, which means you are literate. I am a little baffled why you rail against this technology without even reading about it.

http://www.npr.org/templates/story/story.php?storyId=130052519

These "wifi routers" are working in the white space between channels that was freed up due to the digital conversion, due to the way the channels are allocated by the FCC, when the digital transition was accomplished, each channel needed less bandwidth. Think of it as channel 45.5, not as 45 and 46 are losing their license. When the channels were analog, there was a gap between the channels in order to prevent interference, with a digital broadcast, interference is less of an issue, and this area of "do not use" is now free, the best way to visualize this is to look at a chart of the wifi bands used in 2.4 Mhz:

http://www.radio-electronics.com/info/wireless/wi-fi/80211-channels-number-frequencies-bandwidth.php

if you look at the chart, and the source material for it a bit above, you will notice that for instance, between channels 1 and 6 there is a unused band of 14 khz, if you collected the bands between 1, 6 and 11, you now have 28 khz. When speaking of the TV channels, look how much possible bandwidth is available now that the gaps are no longer needed in the TV frequencies.

Hopefully this post allows you to understand what the FCC is doing, because everything I have seen you comment in this article appeared to be complaints due to lack of knowledge of the subject. Maybe someday we can meet up for beers.

Being self-taught, you've missed our entire discussion on math.

Nobody's talking about adding and subtracting numbers here.

Could your comment be more effete?

BTW, your arrogance is only exceeded by your ignorance.

Perhaps you'd like to tell him, or him that they would "miss" an "entire discussion on math", eh?

You're correct about it being a half-wavelength, but that has less to do with 'range' and more to do with matching the impedance of the antenna with that of the transmitter. An antenna that is a half wavelength and fed in the center is called a dipole, and typically presents an impedance of 50-80 ohms to the transmitter (with most of being purely resistive, one hopes). This arrangement would allow the station to omit a matching circuit, which would be enormous and costly for 2 MW of power.

> I think plugging a cartridge into a SNES is harder than installing a PCI card.

If this is not hyperbole you need to learn about ESD. This is probably what fried your all-in-one's motherboard after GS worked on it. When I work inside a server I'm always wearing a strap. When I work on a customer PC I make sure I'm grounded when before I touch components out of the static bag. When I work on my machines, well admittedly sometimes I roll the dice. YMMV.

One of the design objectives of LTE is reduced latency (compared with 3g) - as low as 10ms. See this page for comparisons with various 3g technologies: http://www.radio-electronics.com/info/cellulartelecomms/lte-long-term-evolution/3g-lte-basics.php In fact the 3G technologies have also been improving steadily.

The sun works on an 11 year cycle. There is also other smaller cycles that run in this. One is a 28 day cycle. These are very important to long range (and short range) communication. Ham(amateur) radio is very influenced(as well as commercial) by this. I am not going to try and explain the whole thing here but try this link for anone that would like to learn more about the sloar flux index, k index, a index etc.. http://www.radio-electronics.com/info/propagation/ionospheric/radio-propagation-prediction-solar-indices.php

As your parent says, the combination of two high frequencies only causes amplitude modulation. The beat frequency is observed by your brain. This still requires that both individual frequencies are observed by your ear, which would not work for the old guy. You need a nonlinear element to actually generate the difference frequency (e.g. a diode in an AM-radio receiver).

This is a huge step forward for computer assisted modulation techniques and wide band scanning. However, I should point out one very important limitation: Dynamic Range.

For those of you who are too lazy, read this.

Now let me point out that while the A/D converter is fast, it only has 12 bits. This will give you about 72 dB of dynamic range. Modern reciever design can yeild dynamic ranges of 100 dB or better (depending on how you measure it). Some day we'll get this performace from 16 bit A/D converters. When that happens, expect the designs of radio to change to software over hardware.

This is the trade off for building a reciever of this sort. There is no free lunch folks...

I've seen the same phenomemon with a Nextel phone. Entertainingly, the interference started before the phone rang.

Options include shielded cable for the speakers and/or ferrite beads to clip around the wiring to squash RF on the line.

The multiplexing scheme shouldn't make a big difference to the interference problem, certainly not compared to the modulation and the frequency. If you're interested in knowing whether GSM uses Time Division Multiple Access to keep users out of each other's way, check the GSM tutorial.