4218 Views 10 Replies Latest reply: Aug 25, 2008 12:28 PM by NR2D
The Field Test Mode is part of all GSM or 3G phones, and is intended for use by the carrier and their field engineers in troubleshooting certain type of issues.
The information can be confusing without experience in cellular networking, and is there for the carrier and their field engineers.
Hope this helps,
The most useful part has been removed from the current implementation; it used to show all towers within range and their signal strength. The most useful information in the "new" field test is the number displayed in the upper left corner of the screen (where the bars normally are). This is the signal strength. It is a negative number, so the lower the number the better (i.e., -70 is better than -100). It is also logarithmic, so a small change in numbers represents a large change in signal strength.
The number is not subjective; it is an actual measurement of signal strength; the units are dB-microvolts per meter (dBµV/m). -100 is generally the lower limit of usability; anything above -90 should provide reliable communications but with the possibility of occasionally dropouts if you move around, and -80 dBµ or better should provide excellent service. The best I have ever seen is -60. On my AT&T 3G Aircard I get 400 kbps at -91 and 1.4 mbps above -80.
For a lot more information than you wanted to know see http://en.wikipedia.org/wiki/Signal_strength.
Using this free speed test app from the app store
Signal strength 57 on 3G --- gave me 544K down and 166 up.
Signal strength 57 on Edge - gave me 114K down and 43 up.
Signal strength 51 on Edge - gave me 146K down and 49 up.
Couldn't get a 51 on 3G. Leaning and sticking my arm out the 3rd floor window showed me a fleeting 53, but even going outside circling uphill above the roof and downhill below subbasement gave me no joy - even though good line of sight in any direction could be found.
But, as far as scaling, it looks like the line between 4 bars and 5 is 83 / 85.
4 bars = 85 and higher
5 bars = 83 and lower
Edit: forgot to mention, there are still huge problems with att on 3g. There is no reason whatsoever the app store is unable to load the top 25 apps on 3G when I give it 4-plus minutes, but manages to show that list in under 15 seconds when I turn off 3G.
What. The. H*. >:(
"so the lower the number the better (i.e., -70 is better than -100). It is also logarithmic, so a small change in numbers represents a large change in signal strength"
Also if you change the number by 3 (-70 to -67) you have theoretically doubled your power (ARH ARH More Power!!!) but this does not mean you have doubled your distance. Things like environmental conditions, rain, snow, trees, buildings and even sunspots (to a lesser extent) will affect your transmitted and received signal.