| [Equipment] Should I try using a filter? I'm turning up a new tower site that sits about 200 yards from an American Tower cell site.
I'm seeing noise floors in the 2.4 GHz band at -83 to -85, and I'm considering trying a Hi Q bandpass filter to eliminate some of that noise. Although the noise could be coming from a competitor's tower a few miles away, I'm apt to believe it may be coming from the adjacent cell site, in which case a filter might be well worth $150.
Here's the one I'm considering: »www.l-com.com/item.aspx?id=22047
Anyone (with more experience than me) care to chime in? I wouldn't mind spending $150 to try it out. The insertion loss on the filter is very low, and it seems like an inexpensive solution if it works. |
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| Are you using sector antennas? If so, is the noise the same on all sectors?
If you aren't using sectors, I suggest you do. It helps isolate the problems. |
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| reply to jim_p_price7
Depends on what channels you're using and what you are seeing noise in.
A filter is designed only to filter out noise from adjacent channels, not directly on your channel. So if you're seeing that noise floor on the channel you want to use, it won't do you any good.
Take it as an analogy of using side vision blinders to block out sunlight coming from your side vision. That's all fine and dandy, unless the sunlight is coming from directly in front of you, then you're screwed. |
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| reply to jimbouse1234
said by jimbouse1234 :Are you using sector antennas? If so, is the noise the same on all sectors?
If you aren't using sectors, I suggest you do. It helps isolate the problems.
Yes I'm using sectors.  |
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| reply to voxframe
said by voxframe:Depends on what channels you're using and what you are seeing noise in.
A filter is designed only to filter out noise from adjacent channels, not directly on your channel. So if you're seeing that noise floor on the channel you want to use, it won't do you any good.
Take it as an analogy of using side vision blinders to block out sunlight coming from your side vision. That's all fine and dandy, unless the sunlight is coming from directly in front of you, then you're screwed.
Hi Voxframe, yeah, I understand that. But you don't think that a heavily populated cell tower 200 yards away could be throwing out of band garbage into my sectors? |
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| reply to jim_p_price7
Doubtful. Very doubtful. Cell towers for the most part tend to be very clean. If they are on a licensed band, you can be darn sure they will make sure they're not causing interference. That gets very expensive very fast for them.
And again the filter won't help you if it's a harmonic or something. And if that noise is directly on the channel, you have two problems.
1) It's right on your channel (In the case of a spurious harmonic or something). The filter won't help at all. But this is doubtful it's coming from the cell tower.
2) It's over driving the internal RF circuit somehow. In this case there isn't a holy thing in hell you could do to protect yourself. But this is very very doubtful as cell towers don't piss out that kind of RF. I'm talking FM broadcast transmitter power. Considering the cell tower isn't even the same tower you're on, it probably isn't coming from there.
Can you maybe post some scans or RF plots? Filters don't tend to help very much except if you're trying to avoid cross interference from two antennas really close to each other (On different channels) |
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| reply to jim_p_price7
Airview |
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| reply to jim_p_price7
How would them filters work on ubnt product? |
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| said by treichhart:How would them filters work on ubnt product?
Well, I'm not saying they would work at all - but the ones I looked at go between an antenna and radio using N connectors (my AP is a bullet M2). |
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| reply to jim_p_price7
Just a quick update, guys - I'm basically stupid here. I've been in the industry only 2 years, and this is the first tower I've put up on an elevated location (it's on a hilltop with fantastic line of sight) with an RF noisy environment, so although I've put up towers before, this one, for me, is avery new experience.
I guess I'll need to pick my channels carefully, using Airview to find the quietest ones in each direction. |
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jcremin
join:2009-12-22
Siren, WI
kudos:2 | said by jim_p_price7:I guess I'll need to pick my channels carefully, using Airview to find the quietest ones in each direction.
One note, the channels with the least amount of noise aren't necessarily the ones that will perform the best. One of my towers has a range of noise floors between -79 and -100. Everything is pure crap on most of the channels with -90 or better noise floor. The one that performs the best has a noise floor of -82. |
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| said by jcremin:said by jim_p_price7:I guess I'll need to pick my channels carefully, using Airview to find the quietest ones in each direction.
One note, the channels with the least amount of noise aren't necessarily the ones that will perform the best. One of my towers has a range of noise floors between -79 and -100. Everything is pure crap on most of the channels with -90 or better noise floor. The one that performs the best has a noise floor of -82. I noticed that here as well. The one with an -85 seems to work the best. |
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| reply to jim_p_price7
I have APs that work well in spectrum graphs that are worse than that. With modern firmware on ubnt equipment giving 3,5 and even 8 MHz widths and shifting of the center channel you can slip something in there no problem.
--
OptionsDSL Wireless Internet
»www.optionsdsl.ca |
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| said by Inssomniak:I have APs that work well in spectrum graphs that are worse than that. With modern firmware on ubnt equipment giving 3,5 and even 8 MHz widths and shifting of the center channel you can slip something in there no problem.
How do you get an 8 MHz channel width? I'd seen that before in a forum and wondered how to do it. |
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| 5.5 beta firmware. |
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| Ah. Has that been stable for you on any bullet M2's? |
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jcremin
join:2009-12-22
Siren, WI
kudos:2 | I wouldn't use the 5.5 beta unless they have released an updated beta that closes the major security hole. |
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| said by jcremin:I wouldn't use the 5.5 beta unless they have released an updated beta that closes the major security hole.
That's been closed now for a few beta and all production firmwares.
5.5 beta 11 has been good and stable for both CPE and all production APs and back hauls. Even more stable than 5.3.3
--
OptionsDSL Wireless Internet
»www.optionsdsl.ca |
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jcremin
join:2009-12-22
Siren, WI
kudos:2 | Good to know. I haven't been on the UBNT forums for a little while and the hole hadn't been closed at that point. Glad to hear that they released a new beta with the fixes included. |
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