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Wouldnt waste your money on a amp.

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Alex
Site Admin


Joined: 19 Sep 2006
Posts: 1754
PostPosted: Sun May 11, 2008 6:48 pm    Post subject: Reply with quote
n6gn wrote:
...then and only then, an antenna *at the antenna end* of the cable may help.

i'm sure you meant, an amp at the antenna end... yes?
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n6gn
EVDO Junkie


Joined: 22 Aug 2006
Posts: 295
Location: Northern California
PostPosted: Sun May 11, 2008 7:29 pm    Post subject: Reply with quote
Alex wrote:
n6gn wrote:
...then and only then, an antenna *at the antenna end* of the cable may help.

i'm sure you meant, an amp at the antenna end... yes?

Very Happy Sure did!

(But an antenna at the antenna end is important too!)

n6gn
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EvdoNonLOSuser
EVDO Fledgling


Joined: 14 Mar 2008
Posts: 25
Location: PNW
PostPosted: Sun May 11, 2008 7:57 pm    Post subject: Reply with quote
I wish I had known to buy the antenna I currently have b4 I bought the other 4. Oh, well. It's all a part of learning. I am glad I never bought an amp though. But I did come close. LOL. Thanks for n6gn's input out here. It's been most helpful in my quest for Evdo.
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res0kkw
EVDO User


Joined: 16 Apr 2008
Posts: 62
PostPosted: Mon May 12, 2008 5:54 am    Post subject: Reply with quote
Yeah wish i wouldnt of made the mistake of the amp.


Now i have a 290 dollar paper wieght.

Im gonna get a laptop and see how good of a signal i will get going out side andd riving to the antenna.

Look at this CRAP

src="http://www.dslreports.com/im/50723364/4915.png"></a>

<a href="http://speedtest.dslreports.com"><img border=0 src="http://www.dslreports.com/im/50723625/4397.png"></a>
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Alex
Site Admin


Joined: 19 Sep 2006
Posts: 1754
PostPosted: Mon May 12, 2008 9:27 am    Post subject: Reply with quote
res0kkw wrote:
Yeah wish i wouldnt of made the mistake of the amp.
Now i have a 290 dollar paper wieght.

you bought it from 3gstore? on 05/08?
if so, it comes with a 14 day return policy.
its only a paperweight if you want it to be.
you could ask for an RMA, and return it?
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dhenninger
EVDO Newbie


Joined: 14 Jan 2008
Posts: 10
PostPosted: Mon May 12, 2008 10:20 am    Post subject: Reply with quote
n6gn wrote:
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


Don't forget that Signal to Noise ratio also matters at the Cell Tower. Using an amplifier will increase your S/N ratio at the cell tower, which can help. So, I wouldn't make the broad statement that an amplifier will not help at all.

I would agree that you should get the best antenna you can, but after that an amplifier can help in some cases. An amplifier will not ALWAYS help, but i find that it does help me when in some areas.

A amp is definitely recommended if you have long cable run. The amp should be as close to the antenna as possible.

Dave
(N3UXK)
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n6gn
EVDO Junkie


Joined: 22 Aug 2006
Posts: 295
Location: Northern California
PostPosted: Mon May 12, 2008 11:21 am    Post subject: Reply with quote
dhenninger wrote:


Don't forget that Signal to Noise ratio also matters at the Cell Tower. Using an amplifier will increase your S/N ratio at the cell tower, which can help. So, I wouldn't make the broad statement that an amplifier will not help at all.

Actually an external amplifier *doesn't* (shouldn't) increase the S/N at the cell site!

Though I was particularly focussed above on the effects of adding an amplifier on received (downlink) performance at the handset, the additional gain or power capability of an external amplifier generally doesn't help on transmit (uplink) either.
In the case of EVDO and 1xRTT, the cell site and the handset are engaged in very agressive power control. Several hundred times per second they negotiate proper forward and reverse powers.

What happens when one adds an external amplifier, even one capable of many watts output, is that the cell site and handset negotiate a minimum power that will work. The initial estimate of the handset power is done open loop by the handset, based on the received signal strength of the base, and then the two ends close the loop during a call or data connection and dynamically adjust powers to keep things going. A goal of the voice protocol in a 1xRTT base is to keep equal receive powers at the cell site from all the users in order to maximize capacity.

Because of the way the system is set up, the handset end (with or without amplification) should not ever require significantly more power than the handset alone can provide (often on the order of 100-400 milliwatts). This comes out of the fact that up/down links are generally fairly symmetrical.
Thus, the only thing that adding an external amplifier usually does on transmit is to move some of the DC power requirements for that modest output to from the handset battery to the external amplifier power supply.
If it does anything different from this, it makes the carriers pretty unhappy since it comprimises their system.

Of course the down side of adding either receive or transmit amplifiers is that additional distortion is always created and this helps nobody.

Adding antenna gain, OTOH, helps everyone since it works on both transmit and receive and reduces the amount of power required and thus the interference - possibly also increasing capacity or the ability to re-use spectrum.


n6gn
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