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res0kkw
EVDO User
Joined: 16 Apr 2008
Posts: 70
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 Posted: Sat May 10, 2008 11:36 am Post subject: Wouldnt waste your money on a amp. |
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A anetenna thats much cheaper helped alot more.
Antenna droped me from -115 dbm to -97 and doubled my speed from the 100s to 300 kb download 1 to no bars to a solid 2 bars.
Amp that cost me over 200+ more than the antenna
dropped me anther 3dbm and added a 3rd bar more often but it isnt solid but had no affect on speed wich what i was looking for.I allso thought it would atleast drop me 10 dbm not just 3.
For a few secs it did drop a hole 5 dbm but that quikly went back up.
Uhg 290 bucks down the toilet.Ill post again if it changes.Crosses fingers but not much hope |
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res0kkw
EVDO User
Joined: 16 Apr 2008
Posts: 70
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| Posted: Sat May 10, 2008 11:40 am Post subject: |
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It is staying at 3 bars alot more but i dont get why i can only get 3 or 400 kb download and only like 50 upload IF IM LUCKY
The dbm is jumpy stays mostly at 94 dbm but will jump down to 92 and back up to 96
It helps but not alot |
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dima
EVDO User
Joined: 20 Mar 2008
Posts: 98
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| Posted: Sat May 10, 2008 6:16 pm Post subject: |
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Actually those "drops" from -115 to -97 dBm and so forth, are BOOSTS in signal strength. You get a maximum strength of 0 (zero) right at the tower. These numbers are negative because of their logarythmic nature mathematically, and physically because they represent signal "attenuation" as they increase in the negative direction. Kinda like temperature scales, where -115 is "colder" than -97.
Positive numbers greater than zero would represent amplication instead of attenuation. |
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n6gn
EVDO Junkie
Joined: 22 Aug 2006
Posts: 571
Location: Northern California
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| Posted: Sat May 10, 2008 8:41 pm Post subject: |
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dima wrote:
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Positive numbers greater than zero would represent amplication instead of attenuation.
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While the sign does indicate a comparative difference, in the case of dBm (an absolute level comparing to 'm' ), the comparison is made against 0 dBm, 0 dB relative to 1 milliwatt, as opposed to dB (a comparison between two unspecified levels). It's pretty unlikely your handset will ever see a signal as large as 0 dBm, though not totally impossible if you climb up next to the segment antenna of a cell site.
Antenna gains work the same way, with both relative and absolute values described at different times. As an example, suppose you have two antennas, say antenna A is built in to a handset is as good as a dipole and the antenna B is external and has twice the gain of a dipole.
*relative* gain of A compared to B is 10*log(gainA/B) = 3 dB (A is better than B)
*relative* gain of B compared to A is 10*log(gainB/A) = -3 dB (B is worse than A)
A dipole has a power gain of about 1.5 compared to an antenna with no gain, an isotropic antenna. An isotropic antenna is "mythical", no one knows how to actually build one but it's an antenna with no *gain* or directivity, not an antenna that doesn't work at all! If you had one, it would not matter at all how you pointed it. so:
*absolute* gain of A is 10*log(1.5) = 2.1 dBi (A is 2.1 dB better than an [i]sotropic antenna)
*absolute* gain of B is 10*log(3) = 5.1 dBi (B is 5.1 dB better than an isotropic antenna and still 3 dB better than antenna A)
On the original subject, adding an amplifier to a good handset will not improve anything - if it would why didn't they put it into the handset to begin with? (good preamplifiers are actually extremely cheap these days and the carriers really do want your phone to work well) This is because although it has gain and the signal gets bigger in the handset receiver, the *noise* gets bigger by the same amount as well. What the handset needs(among other things) to extract good/fast data is adequate Signal/Noise ratio.
In this case the absolute signal strength, expressed in dBm, makes no difference. In your example, the signal power may get bigger (less negative dBm for reasonable situations) but the noise gets bigger right along with it (also less negative dBm values). What matters is the *relative* signal/noise ratio, expressed in dB. Except for situations where where there is something wrong with the handset or there is a lot of (cable) loss between the amplifier and the handset, adding an amplifier doesn't improve this ratio!
An improved antenna can increase *both* absolute power and relative Signal/Noise but unless the handset preamplifier isn't as good as an external amplifier, the amplifier will not improve the Signal/Noise ratio.
It sounds like you just found this out the hard way.
n6gn |
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res0kkw
EVDO User
Joined: 16 Apr 2008
Posts: 70
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| Posted: Sun May 11, 2008 5:07 am Post subject: |
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WOW that all just confused me.
So be4 i spend more money on a yagi antenna will that help or should i just stick with what i got? |
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Blazer
EVDO Newbie
Joined: 12 Mar 2008
Posts: 10
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| Posted: Sun May 11, 2008 7:18 am Post subject: |
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| at 92-94 dbm 8.6 miles from the tower, using 50ft of 9913 and 28ft pole with a wilson trucker antenna, from the dallas server i get 898 down 367 up with a 98ms ping, would like to improve also but didnt want to just through money at whatever, from reading the above it seems a good directional antenna would be the direction i may need to go to avoid adding more noise. |
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Alex
Site Admin
Joined: 19 Sep 2006
Posts: 3074
Location: Dallas, TX
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| Posted: Sun May 11, 2008 7:24 am Post subject: |
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res0kkw, did you ever this article and do your "homework"?
http://www.EVDOinfo.com/RSSI
if you post your answers to questions that are at end of article, we can provide recommendations based on experience.
if you aren't willing to drive towards best signal and identify how far you have to go to find it, then all you will be doing is trial and error that could lead to more money down the drain. |
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Alex
Site Admin
Joined: 19 Sep 2006
Posts: 3074
Location: Dallas, TX
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| Posted: Sun May 11, 2008 7:27 am Post subject: |
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Blazer, I would suggest that you also drive in direction of best signal and see how far you need to go to find -80 signal. and when you find it, do signal testing to see how much difference in speedtest there is.
you may find that even at -80 signal, your speeds don't change much... which will be a pretty good indication that you are already getting all that the tower can give, even at your present signal.
if there is a significant improvement in speeds at -80, knowing that distance to better signal, as well as what lies beneath you and that signal (like trees, elevation, etc) -- makes it easier to judge what gear is needed to get you the better signal, at your desired location. |
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res0kkw
EVDO User
Joined: 16 Apr 2008
Posts: 70
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| Posted: Sun May 11, 2008 7:44 am Post subject: |
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Well i would if i had a laptop.Ill be getting one but probly not for a few months.
Theres trees in the line of range in a distance.
Funny thing is when i talked to sprint guy when i was getting the wireless he was saying your in a great area to have good speeds.Whata jk |
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res0kkw
EVDO User
Joined: 16 Apr 2008
Posts: 70
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| Posted: Sun May 11, 2008 7:51 am Post subject: |
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| What i dont get my pings are allways great around low 100s but my speeds averages around 300 and upload now is usualy in the 30s. |
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Alex
Site Admin
Joined: 19 Sep 2006
Posts: 3074
Location: Dallas, TX
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| Posted: Sun May 11, 2008 7:51 am Post subject: |
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| res0kkw wrote: | | Well i would if i had a laptop.Ill be getting one but probly not for a few months. |
for as much money as you've been spending to try things,
you'd be far better off to go borrow a laptop and get it right. |
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res0kkw
EVDO User
Joined: 16 Apr 2008
Posts: 70
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| Posted: Sun May 11, 2008 8:16 am Post subject: |
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Yeah dont know anyone with one.
I should of spent the money i spent on all this stuff on a laptop instead.Guess ill pick a cheap one up next month. |
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n6gn
EVDO Junkie
Joined: 22 Aug 2006
Posts: 571
Location: Northern California
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| Posted: Sun May 11, 2008 10:19 am Post subject: |
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| res0kkw wrote: | WOW that all just confused me.
So be4 i spend more money on a yagi antenna will that help or should i just stick with what i got? |
Sorry. I guess the application is:
Use all the antenna you can, placed as well as you can.
If much distance to good antenna location, use good cable.
If really a lot of cable, ONLY then, use an amplifier.
n6gn |
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res0kkw
EVDO User
Joined: 16 Apr 2008
Posts: 70
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| Posted: Sun May 11, 2008 4:04 pm Post subject: |
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What i dont get rite now my connection is at 4 and 5 bars.
My dbm dropped to 86 for some reason and the speeds are no better. |
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n6gn
EVDO Junkie
Joined: 22 Aug 2006
Posts: 571
Location: Northern California
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| Posted: Sun May 11, 2008 6:38 pm Post subject: |
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| res0kkw wrote: | What i dont get rite now my connection is at 4 and 5 bars.
My dbm dropped to 86 for some reason and the speeds are no better. |
This relates to what I said about amplifiers in general. If you have a good handset or card, adding an amplifier AT the same location WON'T help - ever. You will get higher signal levels (more bars) but you won't get higher Signal/Noise ratio and you won't get higher download speeds.
Using a better antenna is good. Locating your antenna at a better location helps. Adding considerable cable to accomplish this can even be OK. If you add a lot of cable, then and only then, an antenna *at the antenna end* of the cable may help.
n6gn |
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