Which app do you use to scan/debug GSM/CDMA cellular tower signal strength?

Not exactly. The handset has to pass an SAR (specific absorption rate) test in order to convince the FCC that the handset is not going to fry the users brain with too much RF. To make that work, handset antennas are usually located on the side away from the users head, at the bottom of the phone, or backed by a metal shield. On simulations and in an RF anechoic chamber, the antenna pattern is somewhat directional favoring the directions away from the users head.

"Mobile Phone in Vicinity of Human Head - SAR calculation" See Fig 8:

As for the tower antenna patterns being direction, it's a matter of what you consider directional. In the typical 3 sided tower configuration, the sector antennas have a horizontal beamwidth of about 60 degrees. The tower can and does indicate which sector is being used, but that has a granularity of 120 degrees, which is hardly accurate enough to determine anyones position. On systems that use various forms of AGPS (augmented GPS) using TDOA (time difference of arrival), two different towers can obtain a location fix of a handset. That requires double the number of available receivers, two towers that can hear the handset, and the necessary technology. That's why I've only seen it on demonstration projects. It's also useless for locating the tower, which I believe was the topic of discussion prior to this topic drift.

The vertical beamwidth of sector antennas is very sharp. The vertical beamwidth and downtilt angle are the major contributors to what determines the coverage area of a cell site. Too narrow, and signal will go over the heads of users close to the tower. Too wide, and the tower will be talking to gophers and airplanes, not users on the ground. For example, a common Andrew HBXX-6517DS-VTM antenna:

has a horizontal beamwidth of 66 degrees, and a vertical beamwidth of

4.7 degrees. Draw a 5 degree angle on a piece of paper and you'll see the problem. It's bad enough that there are products to vertically align sector antennas to about +/-0.1 degrees. However, that's also useless for locating handsets, unless you want the altitude.

Dinner... gotta run.

--
Jeff Liebermann     jeffl@cruzio.com 
150 Felker St #D    http://www.LearnByDestroying.com 
Santa Cruz CA 95060 http://802.11junk.com 
Skype: JeffLiebermann     AE6KS    831-336-2558

I agree. My comment was only in relation to the locale that Savageduck reported, which was Lake Nac...Naci......eh ... Lake N-something.

Yup. I just ran an Opensignal report for Cupertino, California, and T-Mobile arguably is slightly better than AT&T & Verizon, but they're effectively the same.

AT&T

T-Mobile Verizon

All three maps show holes in the coverage, even in Cupertino, which is essentially near the heart of Silicon Valley.

I travel a decent amount around northern California, given I have grandkids in various schools and kids scattered about with family.

T-Mobile is fine.

Since none of us are gonna run our own tests with three phones in our hands for weeks on end, I would guess the coverage maps are what we'll have to use.

What's the best coverage map site that covers all three carriers? We can arbitrary pick where you live and where I live and see how the coverage goes.

Here is OpenSignal for, say, the middle of Cupertino, for example.

All I did was:

1. Go to
   formatting link
2. Pick the carrier
3. Type in "Cupertino, CA"

I left the zoom level and everything else exactly as it was found. AT&T

T-Mobile Verizon

Looking at those maps, they're about the same, although I could argue there are fewer holes in T-Mobile than in either AT&T or Verizon, but I'll just say they're about the same which is a tenable assertion.

The one that provides LTE coverage. As far as I know, they only have one of those.

In the basement (cellspot is in the garage) I have -78dB currently. If I go into the garage it's about -60dB-65dB, IIRC.

--
'Luck is my middle name,' said Rincewind, indistinctly. 'Mind you, my 
first name is Bad.' --Interesting Times

As a somewhat related aside, in one article I read about tower cell ids, the first number tells you which sector antenna you're using.

So, you can, with a bit of effort, narrow down the tower and the sector that you're connected to.

But it takes work.

Depends on the "major" urban area. For example, T-Mobile is absolutely unusable in Omaha, which is a pretty decent sized city (about a million for its CSA). I could sometimes get signal if I was outside and stood quite still.

OTOH, I looked at it as just one more shitty thing about Omaha.

Sure. At my Mom's house there was no signal at all for Sprint and only "standing in the backyard" signal with Verizon, while both AT&T and T-Mobile were fine.

However, I will say that up until a few years ago it sure seemed like Verizon had fewer than the others. Now I feel like T-Mobile has caught up.

That seems like the best plan.

--
'Is it heroic to die like this?' said Conina. 'I think it is,' he said, 
'and when it comes to dying, there's only one opinion that matters.'

I have two completely different types of CellSpot devices, both of which say LTE.

Here is a photo of one type in my house, called "CellSpot" and "LTE":

Here is a photo of another type alongside it, also called "CellSpot" and "LTE":

They are extremely different, even though the T-Mobile MARKETING calls both of them a "CellSpot" and "4G LTE".

Which type do you have? The whole reason for this thread was to distinguish between the two.

That's absolutely astoundingly high cellular signal strength (RSSI). All the articles put the range at -50 to -110 or -120dBm.

Are you getting that from your T-Mobile micro tower? How do you know? (Because that's the entire reason for this thread.)

Sure they can. The signal include Latitude and Longitude for the tower.

--
One by one the bulbs burned out, like long lives come to their expected 
ends.

Well, at least it's not just with Apple that you pull this sort of shit.

--
When men talk to their friends, they insult each other. They don't 
really mean it. 
When women talk to their friends, they compliment each other. They don't 
really mean it.

Here is the coverage map after typing a search for "Omaha, NE" and not changing anything else about the results, not even the zoom level.

AT&T:

T-Mobile: Verizon:

Overall, for the center of Omaha, Verizon looks better than AT&T which looks better than T-Mobile.

Those maps don't really show the coverage holes, nor are they up-to-date. I.e. Verizon just put in a tower right next to Cupertino City Hall (a fake tree) that has improved coverage.

But the issue is not in urban and suburban areas, it's outside of those areas. Vast areas of California with no T-Mobile coverage at all, and a lot of those places are places that we like to go.

vast areas of california have no att, sprint or verizon coverage.

no carrier covers *everywhere*.

if where *you* go lacks t-mobile, then get another carrier. for others, t-mobile works just fine, even in out of the way areas.

I've had all three, although not concurrently. I go camping a lot, and skiing, where I'm with a bunch of guys, all of whom are on the various carriers.

Over the years, it's been getting better and better on all the carriers, but sometimes Verizon is the lousy one, sometimes AT&T, and sometimes T-Mobile.

As nospam said, they're all about the same. And I've had Verizon, AT&T, and T-Mobile (in that order) in the same location.

However, the only true test would be to have all three similar phones in your hands at the same time for the tests, which nobody is gonna do.

So everyone is just guessing with bad data (sort of like how climate change debates go).

For once, nospam and I agree in principle and in practice.

I completly understand that the data I showed (which implied that the coverage was about the same) could be bad data.

But you have to realize I've heard a lot of bs on the net where people who have one brand think it's better than the other two brands (of anything), even though they, themselves, have never even tested brand B or C. (It just happened on the digital photo group, for example, where people said "preview" was better at X than Paint.NET and then we find out that all those people who said that had NEVER even used Paint.NET once in their entire lives).

My point is that anyone who claims that cellular data sucks for one carrier than the other generally has lousy data points since almost nobody (not even me) carries three similar phones with them everywhere they go.

So if the OpenSignal coverage maps suck, the question simply becomes where can we get good trustworthy coverage data for any particular USA area?

This may or may not be true. My experience is with Verizon, AT&T, and T-Mobile, but while I have had all three (and while I find them about the same in coverage where I live), I had them sequentially, so the only real comparison was the last day with the prior carrier and the first day with the next (which isn't all that scientific).

What we really need is a *reliable* trustworthy coverage map. Does that exist?

Where can we find it?

That's not the signal.

That's decoding the data on it, and reading it. Then finding via GPS the exact location of the terminal, then calculating the direction of the tower.

--
Cheers, 
       Carlos E.R.

you left out sprint.

some do.

mostly.

My GSM phones show a valid lat-long. My CDMA phones show no data. This is with multiple phones on AT&T (GSM), T-Mobile (GSM), Verizon (CDMA) and Sprint (CDMA) in the Monterey Bay area of California. Your experience may be different in other parts of the country or with other system operators.

Finding CDMA towers has been somewhat of a challenge. I tried to map local sites in the late 1990's and gave up in about 2003 (for medical reasons): Yeah, I know it's old, awful, ugly, incomplete, and inaccurate, but it was acceptable for something built 15 years ago using just a text editor.

--
Jeff Liebermann     jeffl@cruzio.com 
150 Felker St #D    http://www.LearnByDestroying.com 
Santa Cruz CA 95060 http://802.11junk.com 
Skype: JeffLiebermann     AE6KS    831-336-2558

sprint towers include lat/long everywhere i've tried. not all phones will show it, however.