GTOV8
join:2006-02-04
47894
| how to scan for AP signal with spectrum analyzer
1. If I put a spectrum analyzer in the same room as a MT with a 5.8GHz sr5 should I see a constant signal at the frequency of the radio when the radio is in AP Bridge mode?
2. How about when it is in alignment mode?
If I can't get any blips at all on the set frequency, should I assume the radio is bad?
Can the router board affect the radio and stop it from working even if I can access the radio and change settings from winbox?
Is the frequency always centered on the selected channel or does it frequency hop? I'm inside an enclosed room and I'm seeing -40db signals all over the place. nothing else is in the room except my laptop (wireless card is turned off) and the MT. we are not near anything that would be putting out this many signals between 5750 and 5850.
Peaks are hopping all over at -40db but none are appearing on the 5805 of the MT. |
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viperm
Carpe Diem
Premium
join:2002-07-09
Winchester, CA
edit:
January 25th, @12:12AM
| Well if you walk outside the room does it getter stronger or weaker? IS there a Cellualr carrior or any other ISP in the same colocation room as you?
I have not seen a true frequency hopping 5.8 setup only 2.4 You should see the center point as a peak of the freq they are set on and then see weaker signals tapper off to each side of center. It also depends on the width of the freq as to how far on each side from center I.E. if they are using 20mhz channels then you will see the center point and 10mhz to each side usually.
Sounds like there is someone else running 5.7 equipment in your room.
In alignment mode the system is just listening and not actively broadcasting such as in AP bridge mode.
I have not seen a router board that has failed allowing the radio to not work, I am not saying it cant happen I just have not seen it yet. What radio card is it? are you sure you have it set to the correct ant? Is the reading you are getting on the spectrum the channel you are on or is it completely different?
What happens if you unplug or turn off the mikrotik completely does the spectrum go blank or do you still see the signal? If you still see it then I would guess like I said above someone else is in the same room using 5.7.. If this is a true tower site the tower owner should know everyone who is located in that room, what frequencies they are running etc.
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ComTrain Certified Tower Climber. American Tower Certified approved contractor |
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cmaenginsb
Premium,MVM
join:2001-03-19
Palmdale, CA
| reply to GTOV8
My take on your questions:
1. If you do not put the SA in a peak hold mode the signal will appear to hop around in a 20 mhz area grouped on the center frequency. (ie 10 mhz above and below). If you use peak hold it will fill in an area 10 mhz above and below the center frequency. This assumes you're using a 20mhz wide channel.
2. This will be the same as #1
If you don't get a signal than the radio is most likely bad. I haven't seen a routerboard stop a radio from working, but the only way to tell for sure is to try a different radio card in it.
The 5 ghz 802.11a based equipment is direct sequency spread spectrum so it doesn't hop. The only 5 ghz hopper I know of is an older Alvarion unit.
I also agree you need to take a reading with nothing of yours on to determine if it's the Mikrotik or something else giving you the varying readings.
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CCNA, Comtrain Certified Tower Climber |
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GTOV8
join:2006-02-04
47894
| reply to GTOV8
well, I'm sitting in a motel room, not a colo room, in a small town and I see the peak hold signals in my hotel room filling in across the chart at -35db!! from 5755 to 5810. There are no holes. So the noise floor is -35db in my motel room across the whole spectrum. In peak mode there is a flat line created right across the spectrum.
I get 2.5mhz blips popping up across the band moving all over the place. They pop up and disppear on all frequencies raising the peak hold to a flat line at -35. I don't see any change in the signals when I unplug the MT power. These signals are SO strong though. As far as I know there isn't anything else around here. The 2.4 signals are zero. There are none at all except for the AP I talk to for this link. No other 2.4 blips at all. Then I go to test this MT AP and the entire band is full of signals. I have a 5 inch whip on the SA and I can stick the unit in the bathroom and close the door and the signals are just as strong. I'm not sure what the heck I am seeing. At -35dbm, I don't even know for sure that the MT is working because they are scanning across the band so fast I really can't tell if turning off the MT is changing anything. It's kinda weird. I'm use to seeing those 20mhz channels. Not the entire band having a peak of -35db. There are some strong signals here and I can't figure this out. This is a mom & pop old budget motel. They don't have any electronics. At least the TV works. |
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GTOV8
join:2006-02-04
47894 | reply to GTOV8
wow there's a string of strong signals all the way out to 6.1 ghz. they drop down from -40dm to -57 dbm but they fill the entire spectrum. Any idea what this is? |
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GTOV8
join:2006-02-04
47894
| reply to GTOV8
here is a scan with the MT OFF. it's unplugged. I had the center freq at 5765 sitting on the bed with a 5dbi whip. I can turn it on and turn it off and see no change, but how would I know in this mess with these strong signals in my motel room in this little town. I can't imgine right now where this is all coming from where I am. |
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lutful
Premium
join:2005-06-16
Ottawa, ON | 5.8Ghz cordless phones? |
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AnonDOG
@freeantennas.com | reply to GTOV8
Is there an electric fence nearby? |
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GTOV8
join:2006-02-04
47894
| reply to GTOV8
Well here is a pix of a peak hold run over about 10 min from the front seat of my car about 5 miles out into nowhere TOTALLY SURROUNDED BY 500ft and higher mountain peaks in a valley. From this location 360deg all you can see are the sides of mountains. there is not a building in site. These signals are a practically a constant -40. As I was driving around I found only a few spots over a 15 mile area where they went away for a few hundred feet as I was driving. There is a military base about 30 miles away, but it's behind a 9,000 ft peak between us and there are no towers on the peak. These are awful strong and consistent power levels. This scan shows the spectrum from 4ghz to 6ghz. Do others of you see this kind of use?
If I am trying to do a 5.8ghz backhaul does it stand a chance? I don't see ANY frequency use on the MT use scan. Nothing shows up at all. I just get this crazy stuff with the SA.
Check out the -25 peak. I mean I'm sitting miles away from the nearest building in a hole. |
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superdog
I Need A Drink
Premium,MVM
join:2001-07-13
Lebanon, PA
 ·WaveCrazy.Net
| said by GTOV8  :Check out the -25 peak. I mean I'm sitting miles away from the nearest building in a hole. I am going to guess here and say that maybe what You are seeing is harmonics from another transmitter?. Maybe it is an issue with radar, as the power levels they use could be very high?.
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GTOV8
join:2006-02-04
47894
| reply to GTOV8
according to pacwireless, even though these are strong signals as long as they are frequency hopping, my backhaul signal at -65 should still work on focused narrow beam high gain grids. Especially if the MT can't see the signals on a frequency scan. That sound right? |
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superdog
I Need A Drink
Premium,MVM
join:2001-07-13
Lebanon, PA
·WaveCrazy.Net
| said by GTOV8 : Especially if the MT can't see the signals on a frequency scan. That sound right? Yep. 
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cmaenginsb
Premium,MVM
join:2001-03-19
Palmdale, CA
| reply to GTOV8
GTO, what are you using as an antenna on the SA? When doing a survey for a backhaul I always prefer a directional antenna to give yourself a more realistic picture.
It could be harmonics or it could actually be something from the military base. Here in CA I have seen some interesting things even being NLOS that seem to come from the military.
I would also suspect a possible bad SA as well. When you get back to a place you know I'd set it up and see if you see the same thing.
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CCNA, Comtrain Certified Tower Climber |
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