Results 1 to 6 of 6

Thread: LTE Antennas & Signal Strength Measurement: How does dBi translate into dBm?

  1. #1
    Join Date
    Sep 2004
    Location
    Greater D.C./Baltimore Metro Region, USA
    Posts
    1,926
    Device(s)
    BlackBerry Key 2, VZW AC791L Jetpack, MoFi 4500 SIM4 V. 2 LTE Gateway, Moto Z2 Force w/ Keyboard Mod
    Carrier(s)
    ▪T▪ ▪ ▪Mobile▪, Verizon Wireless
    Feedback Score
    0

    Question LTE Antennas & Signal Strength Measurement: How does dBi translate into dBm?

    Hi everyone, I have what some of you will no doubt consider a rookie question, but I'm having trouble understanding it from what I've read so far. And I know someone here will have the answer.

    I recently bought a MoFi 4500 SIM 4 Version 2 LTE Router. This is the All Carriers model that can be used on ANY carrier in North America, Europe, and possibly other parts of the world, as well. It looks like this:



    The 4 antennas there are all standard 5 dBi antennas about 6-7" long, 2 for the WiFi routing functions, and 2 for the LTE radios.

    Using only those included antennas, I know what kind of LTE signal strength I can get on both Verizon Wireless and T-Mobile. But I've just ordered 2 14" long, 9 dBi LTE antennas to boost the signal gain.

    I've done a quick Google search and read about both dBi and dBm. Unfortunately, I'm neither an engineer, nor a technician, and thus I haven't studied the high level mathematics involved in calculating all this stuff.

    All I want to know is this: If the 5 dBi antennas give me a signal strength of -89 dBm on T-Mobile's Band 4, what can I expect to boost the signal strength up to by using 9 dBi antennas? So far, I haven't found a simple, easy explanation of how to determine that.

    Thanks in advance for any additional info any of you can provide.
    Photobucket's policy changes SUCK!

    New signature coming soon-ish...

  2. #2
    Join Date
    Sep 2016
    Posts
    3
    Feedback Score
    0
    Hey Jack,

    Since I've been following a lot of topics you've been participating in, I thought I'd share this link with you; (I guess I can't post links. Yet. Sorry.)

    It's just a quickie 'practical' summation of what you can expect.

    I've got some experience in wireless of various flavors, having worked a WISP with my brother-in-law for a few years, but he's the one with the in-depth radio and wireless background. I may ask him to explain it in 'simple speak' for me, and relay that to you. Realistically though, I wouldn't expect a big gain in signal strength with just a stick antenna like that. Using directional antennas, like the Yagi, coupled to actual boosters, will give you much better performance. However, they can have a substantial cost associated with them.

    I've recently put up a Yagi on top of my home, on a 10-foot push-up mast, coupled to some Z-Boost equipment. This gave me a substantial increase in strength inside my home, as the booster re-broadcast locally. I basically went from no 'bars' on my main floor, to almost full signal. This comes with a $400 pricetag though.

  3. #3
    Join Date
    Sep 2013
    Posts
    234
    Feedback Score
    0
    Quote Originally Posted by uncooldude View Post
    Hey Jack,

    Since I've been following a lot of topics you've been participating in, I thought I'd share this link with you; (I guess I can't post links. Yet. Sorry.)

    It's just a quickie 'practical' summation of what you can expect.

    I've got some experience in wireless of various flavors, having worked a WISP with my brother-in-law for a few years, but he's the one with the in-depth radio and wireless background. I may ask him to explain it in 'simple speak' for me, and relay that to you. Realistically though, I wouldn't expect a big gain in signal strength with just a stick antenna like that. Using directional antennas, like the Yagi, coupled to actual boosters, will give you much better performance. However, they can have a substantial cost associated with them.

    I've recently put up a Yagi on top of my home, on a 10-foot push-up mast, coupled to some Z-Boost equipment. This gave me a substantial increase in strength inside my home, as the booster re-broadcast locally. I basically went from no 'bars' on my main floor, to almost full signal. This comes with a $400 pricetag though.
    Can u post pics of your setup?

  4. #4
    Join Date
    Jul 2007
    Location
    Southern California
    Posts
    1,608
    Device(s)
    Motorola G6
    Carrier(s)
    Page Pluss
    Feedback Score
    0
    >Question LTE Antennas & Signal Strength
    >Measurement: How does dBi translate into dBm?

    Okeh. Shorter e-mails are probably better.....

    >The 4 antennas there are all standard 5 dBi antennas ....

    >But I've just ordered 2 9 dBi LTE antennas ...

    dBi and dBm are two different things. dBi is an
    antenna number and dBm is a power level.

    Engineers and techs use dB for convenience ; it replaces
    some awkward numbers that are multiplied with convenient
    numbers that are added and subtracted.

    Truely, if the antennas do what they say, the 9dBi antennas
    should be 4 dB "better" than the 5 dBi antennas.

    >I haven't studied the high level mathematics involved ...
    IMHO, you must have studied logarithms in high school.

    >All I want to know is this:

    Ahh! We cut to the chase ...

    >If the 5 dBi antennas give me a signal strength of -89 dBm
    on T-Mobile's Band 4, what can I expect to boost the signal
    strength up to by using 9 dBi antennas?

    If everything works as promised, you should expect to see
    a 4dB improvement. Therefore, you should expect to
    see -85 dBm.

    Keep in mind, there are system considerations involved
    and the numbers you see without careful setup and sensitive
    laboratory equipment will be all over the place.

    If you want to do this face-to-face, your local ham radio
    club probably does a program on this subject about once a year.

    Regards, FJ

  5. #5
    Join Date
    May 2017
    Posts
    51
    Feedback Score
    0
    I am also interested in this as well. I have a mobley operating with a line of sight tower that is around 4000 feet from my house. With it against a window facing the tower I have a signal strength of -75db at around 15-25 Mbps download. I am wondering if it would be worth using a external directional antenna to improve the signal strength even more, and would that provide more bandwidth speed? Basically would the effort and expense yield a big enough benefit?

  6. #6
    Join Date
    May 2010
    Posts
    55
    Feedback Score
    0
    Below are two links that may answer your question or at least give you a start......

    http://s4gru.com/index.php?/blog/1/e...rength-primer/

    http://blog.industrialnetworking.com...gthsignal.html
    Last edited by Licklog; 05-19-2017 at 06:17 AM.

Similar Threads

  1. LTE vs HSPA signal strength
    By Positive Climb in forum TELUS/Koodo/Public Mobile
    Replies: 11
    Last Post: 06-06-2017, 05:24 PM
  2. Signal strength measurement on E815
    By jonathanedwards in forum Feature Phones
    Replies: 4
    Last Post: 06-28-2006, 03:33 PM
  3. phone antenna modding/signal strength
    By chemikaldreem in forum Motorola Modding
    Replies: 0
    Last Post: 02-10-2006, 09:20 PM
  4. Replies: 4
    Last Post: 06-26-2004, 08:45 PM
  5. Replies: 7
    Last Post: 11-20-2003, 06:42 AM

Tags for this Thread

Bookmarks