 Jim_in_VA
join:2004-07-11
Cobbs Creek, VA
kudos:4 | 900 ..what causes the interference LTE at 1900 and 700 is not the problem is it? Whats the problem with 900?
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WHT
join:2010-03-26
Rosston, TX
kudos:5 | SCADA telemetry radios, baby monitors, wireless cameras, other WISPs...off the top of my head. |
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LLigetfa
join:2006-05-15
Fort Frances, ON
kudos:1 | reply to Jim_in_VA
Smart meters, RFID, cordless phones, wireless speakers, amateur radio, shipborne radar, pagers, etc.. |
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 InssomniakThe GlitchPremium
join:2005-04-06
Cayuga, ON
kudos:1 | reply to Jim_in_VA
Some cordless phones marked as 5.8ghz have a 900mhz return path. Dumb.
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 John GaltForward, MarchPremium
join:2004-09-30
Happy Camp
kudos:5 | reply to Jim_in_VA
900 MHz cordless phones with external, roof-mounted antennas... |
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InssomniakThe GlitchPremium
join:2005-04-06
Cayuga, ON
kudos:1 | said by John Galt:900 MHz cordless phones with external, roof-mounted antennas... You are not supposed to do that! Shame...
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| reply to Jim_in_VA
The list is endless. Some tractor companies i.e. Atlantic Tractor - John Deere and Hoober are experimenting with a 900mhz/GPS hybrid system for tracking tractors and combines.
If you are asking because you wireless service is having issues and your WISP is blaming it on interference this should be posted in the Wireless Users area.
Unless something has changed, you don't have, work for, or have any connection with a WISP other than being a customer. |
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lutful... of ideasPremium
join:2005-06-16
Ottawa, ON Reviews:
 ·TekSavvy DSL
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said by Jim_in_VA:LTE at 1900 and 700 is not the problem is it?
Even the cheapest ceramic filter IC for 900Mhz ISM band are "designed" to attenuate by more than 40dB. Actual performance varies and it is possible that very high power cellular or other licensed transmitters could bleed into the ISM band.
BTW, these are much closer to the ISM range (902-928Mhz):
LM Base TX from 935-940 MHz paired with LM Mobile TX from 896-901 MHz
Narrowband PCS from 901-902 MHz, 930-931 MHz, and 940-941 MHz.
Fixed from 928-929 MHz and 932-935 MHz.
Paging from 929-930 MHz and 931-932 MHz. |
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1 edit | reply to Jim_in_VA
said by Jim_in_VA: Whats the problem with 900?
Though they "shouldn't" cause interference Hams are allocated secondary use in the 902-928 mHz 33 cm band.
»www.arrl.org/files/media/News/33···raft.pdf |
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Jim_in_VA
join:2004-07-11
Cobbs Creek, VA
kudos:4 Reviews:
 ·Northern Neck Wi..
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This interference is among many 900 users, not just one or two. The 2.4 radios are having no issues. So it is wide spread among the network. The WISP owner is a friend of mine and I suggested this forum for him to seek suggestions for cause and solutions. I have alternative means for internet access, I'd just like to help him out with a obvious perplexing problem he is having. His customers on 900 are getting hot under the collar.
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InssomniakThe GlitchPremium
join:2005-04-06
Cayuga, ON
kudos:1 | Well one thing about widespread and consistent interference is that it's easy to find! What does a SA show?
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Jim_in_VA
join:2004-07-11
Cobbs Creek, VA
kudos:4 Reviews:
·Northern Neck Wi..
| He stated his SA was simple and limited for snooping. Another point he made was The interference, when it happens is right on top of us, all four channels that we can use. The noise floor is usually around -94. When the interference hits, the 900 noise floor raises to -50 and stays for about 10 minutes and then disappears. It knocks the 900 customers offline. When the interference
goes away, we have to reboot the data pole, because it has locked up to protect itself from overload
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WHT
join:2010-03-26
Rosston, TX
kudos:5 | reply to Jim_in_VA
said by Jim_in_VA:to seek suggestions for cause and solutions Well...We posted causes. The 900 band was usable years ago, but is now a trashed wasteland - the better solution is to move the problem users to 5.4-5.8 band. |
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Jim_in_VA
join:2004-07-11
Cobbs Creek, VA
kudos:4 | Heavily forested area WHT, don't think that will do it
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WHT
join:2010-03-26
Rosston, TX
kudos:5 | reply to Jim_in_VA
said by Jim_in_VA:When the interference hits, the 900 noise floor raises to -50 and stays for about 10 minutes and then disappears. How often during the day? Is it a timed event? Some SCADA systems keep the AP quiet until it has to query remote sites. |
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Jim_in_VA
join:2004-07-11
Cobbs Creek, VA
kudos:4 | That I don't know |
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WHT
join:2010-03-26
Rosston, TX
kudos:5 | That would be a great help to know. |
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Jim_in_VA
join:2004-07-11
Cobbs Creek, VA
kudos:4 Reviews:
·Northern Neck Wi..
| The SCADA system is a good observation. The county recently upgraded the sewer/waste water system and has several stations along the route. Do they use 900 for reporting?
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| said by Jim_in_VA:The SCADA system is a good observation. SCADA is usually short bursts of data as the unit is polled. |
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Jim_in_VA
join:2004-07-11
Cobbs Creek, VA
kudos:4 | that enough to knock customers offline?
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| reply to Jim_in_VA
said by Jim_in_VA:When the interference hits, the 900 noise floor raises to -50 and stays for about 10 minutes and then disappears. I’ll bet that is automatic meter reading (AMR), with most of those systems the head end, at set intervals polls the collection points, which in turn polls the end points (meters) and when something like this fires up, it could easily cause what you are describing and with the collection points being high up on the utilities poles and spread all over the place and utilizing spread-spectrum, they alone could blanket a WISP system with interference that is seemingly coming from everywhere.
Add to that the smart meter turn-up schedule for that area.
»www.dom.com/about/conservation/p···dule.pdf |
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said by Jim_in_VA:Heavily forested area WHT, don't think that will do it And another reason a utility might pick 900 and the fact that utilities see 900 as abandoned by a majority of their subscribers, whereas if they deployed 2.4 or higher they could interfere with home wireless systems catching them a lot of flack. |
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| reply to Jim_in_VA
said by Jim_in_VA:that enough to knock customers offline? Yes but most SCADA systems don't have a lot of endpoints so the interference while on a regular basis would be short lived. |
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 your moderator at work
 hidden : Personal attacks
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lutful... of ideasPremium
join:2005-06-16
Ottawa, ON Reviews:
·TekSavvy DSL
| reply to Jim_in_VA
Re: 900 ..what causes the interference said by Jim_in_VA:When the interference hits, the 900 noise floor raises to -50 and stays for about 10 minutes and then disappears. It knocks the 900 customers offline. Think carefully and logically.
a) RSSI of -50dBm means a very strong ISM band transmitter, probably located within a mile of the CPE.
b) But many different CPEs are being impacted and they are probably scattered in a much larger area.
c) So the transmitter needs to be located near the middle of those CPEs and at quite high elevation. It could even be co-located with the WISP's 900Mhz AP on same tower.
said by Jim_in_VA:When the interference goes away, we have to reboot the data pole, because it has locked up to protect itself from overload Just because of -50dBm RSSI? But RSSI often exceeds -30dBm during AP-CPE bench tests !!!
A good RF front-end design should handle at least 0dBm RSSI for several hours. Meanwhile good AP and CPE firmware will recognize when the receiver is in saturation and just keep reporting an error condition without needing a reboot.
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WHT
join:2010-03-26
Rosston, TX
kudos:5 | reply to Jim_in_VA
said by Jim_in_VA:Do they use 900 for reporting? ...
that enough to knock customers offline? Depends on the duty cycle. If the AP stays quite until it starts polling the remotes, then the problem would be intermittent like you are beginning to describe. If the AP starts up, then the remotes start transmitting.
said by Jim_in_VA:The county recently upgraded the sewer/waste water system and has several stations along the route. That might be an important clue. |
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your moderator at work
hidden : Trolling
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kc9sqr
join:2011-11-10
Rockford, IL
2 edits | reply to MatrixHDV
Re: 900 ..what causes the interference It's just as much of a wasteland for hams as it is for you guys for the same reasons... Most of us prefer to stay away from the allocations that we have to share with part 15 devices.. Thankfully though most ham users don't use that much of the spectrum, but can usually find a semi clean portion of the band to use when they do decide to use it...
I've heard from a few people about a 33 cm repeater around the area, but I've never heard a peep out of it and have been listening for it for at least 6 months now..
Reason for edit... Nearly 3 am and multitasking while posting... |
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InssomniakThe GlitchPremium
join:2005-04-06
Cayuga, ON
kudos:1 | reply to Jim_in_VA
I can't say I do too bad in 900mhz. I have probably a hundred customers on it throughout my network and rarely a peep. Just did 14 megabit from a loaded AP that is legacy xr9-nstreme in 10mhz just the other day
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your moderator at work
hidden : Trolling
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