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ekkas
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Bad signal/interference?

Wed Jun 28, 2006 7:58 pm

Please help. I must install a tower with AP 'last week' and just have problems I can't seem to solve. Never had so much headache on an installation. Did about 9 previous similar installations with 'no' problems.

Here's the breakdown:
RB500 with daughterboard
NMP5354 MiniPCI card for 5.8 GHz uplink
NMP5354 & CM9 cards for APs

At first I tried to set up two 180' sector antannas, but now I've just got one 15dbi omni

Here's the problem:
My 5.8GHz uplink is 100%(?), I do a bandwidth test at about 30Mbs solid.
My AP... If I'm very close to the tower, I can connect.
If I'm +-70m away with a laptop (Intel 2200BG card) it shows 100% (excellent)signal strength, but i can not even get ping responses. I've changed the channel to 2412 (ch1 - 802.11b only) and then I get very poor & inconsistent responses. Even if I'm up on the tower(2m away), my pings are 50ms+ Tried long/short/both preamble. Checked 'Frequency scan' from WinBox and it seems like almost no other radios in there.

Here's the scenario:
There are 9 cellphone sector antennas on the same tower
2 radio antennas (police radio repeaters) and security radio antennas.

My Mikrotik support guys said that cellphone towers & radio should have no interference, but I get very, very bad trhoughput. Even with a 19db grid antenna about 1km away, I barely get ping responses & cannot even remotely open WinBox so bad is it.

My routerboard is mounted in a plastic box lined with aliminium foil on the inside to try & minimize interference to the police radios on the tower. No shorts, plastic mountings.

Please help. I need to get this tower working nicely and have many people on my back...

From this info, is there anyone out there who can 'see' what I did wrong? I don't own sprectrum analysers & other specialized equipment, so I don't know where to start looking.

I also replaced with other cards & antennas but always the same problem.

Any help desperately needed.

Thanks

Ekkas
 
believewireless
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Wed Jun 28, 2006 8:18 pm

Are you sure you have the correct antenna setting? Try switching between antenna a and antenna b to see if it fixes the problem.

Could it be that you aren't using WDS to bridge the connections?

Also,
 
ekkas
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Wed Jun 28, 2006 9:10 pm

Thanks for that comment, your brainwaves must have reached me before the post. :-)
I tried it with 'antenna b' setting and could see 2 AP's that I couldn't see before. It's now 9pm here, so I drove out to the tower with my laptop to check, but the same problem. :-(

The only thing I can think is that my uplink is straight on the RB, but my AP card(s) are on the daughterboard. Maybe a faulty daughterboard or RB/DB interface?

I don't know how to WDS my aps, so I give it different SSID, IP range & channel.

You said also, ..... then the post cuts off.

Thanks for your reply.
 
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alex23
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Thu Jun 29, 2006 12:11 am

If you see the diagram of an omni you will see that it is like an umbrella
When you are exactly under the omni you get almost nothing but if you get 200 meters away you will get a very good signal.
Perhaps the sector is the best solution for you

you should have the right antenna for the band to 802.11b,it will not work if you have an omni for 5ghz
 
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djape
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Thu Jun 29, 2006 10:20 am

If you see the diagram of an omni you will see that it is like an umbrella
When you are exactly under the omni you get almost nothing but if you get 200 meters away you will get a very good signal.
Agree, signals will just go over your head. Pack your things and test from a distance...
I drink like a pirate and smoke like a hippie...
 
ekkas
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Thu Jun 29, 2006 2:03 pm

Thanks guys, but I've tested it from right next to the omni (same height), same story. From far I cannot even connect. Went back there this morning and the strange thing is if I plug the pigtail out, I get same signal!!! RunningWindows bandwidth test from laptop to RB and with or without antenna plugged in, it's exactly the same. Replaced card, cables & antenna. No go. Weird is not the right word...
 
tully
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Thu Jun 29, 2006 7:33 pm

Maybe you have to use the newest version and set the

proprietary-extensions=post-2.9.25

This is in the wireless menu. The Intel driver might need this change.
 
MimiFleX
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Location: France

same problem

Wed Jul 05, 2006 2:44 pm

Hi there,

I've got a similar problem with 3 RB532 with CM9 cards. These RB are running RouterOS 2.9.26. I notice that when I plug the 2,4GHz antenna, the signal level is the same, or worst. I tried many 2,4GHz antennas and many other coax cables to be sure, it's the same problem.

One time, I switched from ant-a to ant-b setting, nothing better. I switched back to ant-a and the signal increased (+20dB). I think this could be a bug in the RouterOS which not correctly handles antenna mode, or even power, (or impedance ?? On a site I had better results on 2.9.26 when N connector was half screwed, I'm sure the cables and connectors are all good).
I also tried to use both pre and post-2.9.25, same result.

Also I notice that my APs disappears 2 or 3 seconds every 30s.
I tried many other CM9 cards, reset configuration twice (via serial port).

I'll try to downgrade to an older RouterOS. I had no problem before with factory RouterOS version (under 2.9.23) on more than 30 RB532.

I was unable to replace an old prism2 based AP by a RB532 + 2 CM9 on a site last week (200km and a climb for nothing), because no customer appeared in the registration list. Same antenna, same coax.

Regards
 
nswizard
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Thu Jul 06, 2006 12:47 am

Same problem over here. After an upgrade i had to change my pcmci Prism card with minipci Atheros cm9. Users close to AP (200m, 500m) could not work and 3 km users works just fine. I spent 3 days trying with diferent settings (b,g) and then when i installed minipci with prism chipset all is back to normal. ?!?!?!?!??!
 
ekkas
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Thu Jul 06, 2006 2:03 pm

That is just to weird.I've got +-10 CM9 & NMP5354 cards lying around that I tried, with the same results, so it couldn't be a faulty card. I'll see if I can get one of those Prism chipset cards...
 
MimiFleX
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Location: France

Mon Jul 10, 2006 7:21 pm

does someone have some news about that very strange problem ?
I have downgraded to RouterOS 2.9.3 and did a /system reset.
All seems to be ok now. I'll make others tests (upgrade and see the difference with the same antenna, same cables, same CPE).
 
UniKyrn
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Mon Jul 10, 2006 7:49 pm

Cell towers can and do cause problems with 802.11b stuff. The problem appears to be the RF plasma "cloud" surrounding their antennas because of their much higher power output. You wouldn't think this was true just looking the the frequencies in use and their harmonics, but I've seen it happen in real life.

I don't think you're going to have much luck getting your AP working at that location, at least not at 2.4Ghz.
 
maxfava
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Mon Jul 10, 2006 9:07 pm

does someone have some news about that very strange problem ?
I have downgraded to RouterOS 2.9.3 and did a /system reset.
All seems to be ok now. I'll make others tests (upgrade and see the difference with the same antenna, same cables, same CPE).
MimiFleX,
I'm facing the same issue from 1 month. But I have used for the first time RB, before I have used RouterOs as server in a PC based, never for wireless.
Using CM9 as using NMP5354.
What I have seen in both the boards is that the behavior is better from channel 1 to 6 while from channel 7 to 11 the communication between clients and AP is worst.
Periodically I cannot get ping response from the clients for about 2 or 3 minutes.
The signal form the registration table for a particular client near to the AP is about -55 and SNR is 42db, while the worst client is about -70 with SNR of 22db.
The clients are not disconnected by wireless, but seems that there is no route between the AP and the clients . I have using simple bridge between wireless and WanEthernet.
If your trials are positive, try to use the NMP5354 (if you have one) becouse this is last Atheros chipset, and I have dubt about the older drivers.

Best Regards
Max
 
maxfava
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Mon Jul 10, 2006 9:16 pm

RB500 with daughterboard
NMP5354 MiniPCI card for 5.8 GHz uplink
NMP5354 & CM9 cards for APs
I'm the dubt that with the mixing of NMP5354 and CM9 the RB :? ... has problem. Is there some one that have tested only CM9 or only NMP5354 on a single RB?
 
ekkas
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Mon Jul 10, 2006 11:47 pm

RB500 with daughterboard
NMP5354 MiniPCI card for 5.8 GHz uplink
NMP5354 & CM9 cards for APs
I've tried to make one AP with 5354 or the AP with CM9 (uplink stays 5343) but with same problem...

I've removed equipment from tower & took to my home and here it is fine, so I'm in the dark here. Might be site-specific...? Don't have spectrum analyzer, so can't anything but what the interface/scan shows me. :cry:

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