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jon8105
EVDO Heavy User
Joined: 05 Dec 2006
Posts: 147
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 Posted: Tue Jul 24, 2007 8:35 am Post subject: Will a single band antenna help? |
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I am getting a lot of noise (high Ec/Io) which is causing my signal to stay inconsistent, but I am not exactly sure what is causing it. I have an AC595 card, yagi antenna and an amp. I got a new card and I have bypassed the amp and I am still getting the same results, therefore, I think it is either the dual band yagi or the adapter cable.
Could it be that since this is a dual band yagi and it is pulling in both 800 MHz and 1900 MHz that I am getting noise? If so should I get a single band (1900MHz) antenna and see if that fixes the problem? I will also try a different adapter to see if that is part of the problem.
Anyone else have this problem or have any suggestions as to what could cause my singal-to-noise ratio to fluctuate and stay high?? |
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n6gn
EVDO Junkie
Joined: 22 Aug 2006
Posts: 347
Location: Northern California
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| Posted: Tue Jul 24, 2007 9:28 am Post subject: Re: Will a single band antenna help? |
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| jon8105 wrote: |
Anyone else have this problem or have any suggestions as to what could cause my singal-to-noise ratio to fluctuate and stay high?? |
I'm not sure of your metric but think Ec is usually energy-per-chip and having a high number there should be a good thing.
If you really are in a situation where you have a high total power (signal + noise) level but low signal power thus creating a low Signal/Noise ratio, it may be because you have a strong signal sharing the RF channel with the (weaker) signal you want.
Put another way, unusable (interfering) CDMA signal from a nearby tower, probably in a different direction, is larger than the one your system is trying to use. I'm not sure how that can happen since usually the spectrum (RF channel) all belongs to a single provider in a given area. If that's the case, one might expect the handset to simply use the stronger signal.
However, if it's the case that you do have a same-RF-channel interferer, a directional antenna might help a great deal. It not only allows you to increase the signal in the desired direction, but it does this by diminishing signal from undesired directions.
I find it very unlikely that a passive element like a cable or antenna, per se, would generate significant noise (beyond the thermal noise associated with the lossy (having attenuation) elements within it, which is small). If one is *very* close to multiple strong signals on different frequencies it is possible for non-linear elements in passive structures to generate on-channel noise but this is normally a special condition and would only show up in high-RF environments like hilltop sites and perhaps right at a cell site. Corroded joints on towers and such on hilltops occasionally do this. In spite of some 'common wisdom' to the contrary, the low-microwave spectrum really is pretty quiet and the about the only noise one sees is from intentional radiators (transmitters) operating on their intended channel.
Try a directional antenna and see what happens.
n6gn |
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jon8105
EVDO Heavy User
Joined: 05 Dec 2006
Posts: 147
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| Posted: Tue Jul 24, 2007 9:53 am Post subject: |
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The yagi antenna I have is a directional antenna. I apologize, I didn't mean high in a number sense. My signal Ec/Io is at around 10 with just my card connected, however, when I plug in my antenna/amp, or even just my antenna, it goes down to about -25 and fluctuates. A lot of the times it goes to -63, which is I think unreadable and then my connection dies. However, with the card it stays consistent at around 10!
| Quote: | Ec/Io
The ratio of signal energy measured within a single chip duration of the pilot signal against the power spectrum of interference and noise.
In other words your signal strength might look fine but the Ec/Io might be too low (network noise and interference) to allow a reliable EVDO connection. |
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n6gn
EVDO Junkie
Joined: 22 Aug 2006
Posts: 347
Location: Northern California
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| Posted: Tue Jul 24, 2007 11:19 am Post subject: |
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| jon8105 wrote: | The yagi antenna I have is a directional antenna. I apologize, I didn't mean high in a number sense. My signal Ec/Io is at around 10 with just my card connected, however, when I plug in my antenna/amp, or even just my antenna, it goes down to about -25 and fluctuates. A lot of the times it goes to -63, which is I think unreadable and then my connection dies. However, with the card it stays consistent at around 10!
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I would begin to wonder if the external antenna connection or adapter cable for your card is OK or not. Generally just plugging the connector into the external jack will cause the card to switch from internal to external antenna. It almost sounds like it is switching but not making contact with the center conductor of the external(adapter cable) coax. If you have a continuity tester, you might make sure that the center connection of the adapter cable is continuous as well. If it is, this doesn't rule out a switching problem on the card but at least it is one less thing to wonder about.
n6gn |
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jon8105
EVDO Heavy User
Joined: 05 Dec 2006
Posts: 147
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| Posted: Tue Jul 24, 2007 11:25 am Post subject: |
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| I have tried two different cards, so I don't think that it is the card. However, I talked to the guy where I bought the antenna/amp/adapter cable and he said it is not the equipment, but that it is the positioning of my antenna! I will try and do some more adjusting tonight and tomorrow, but if that doesn't work I want to try another adapter cable. I like the speeds of EVDO when I have them, but I hate all of the inconsistencies I keep running in to!!!! |
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