Interference or intermod from cellular mobile sites?

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  • Updated 5 years ago
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Anybody had throughput problems when APs are in a close proximity to cellular mobile sites?
Thinking of outdoor mounted APs when the cell site is only tens of metres away.
Our issue may be from intermod products generated inside the Access Point.
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Jason Hills

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Posted 5 years ago

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Scott M., Sr. Support Engineer

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Out of band interference is always a potential issue with any wireless communication technology. Its not just cellular sites, but Radio, TV and any really powerful RF signal. I've seen people mitigate situations like the one you described by making use of shielded cable, and/or ferrite beads (top and bottom) and/or putting the POE cable inside a metal conduit. Without shielding or other mitigating measures, the POE cable can act like an antenna allowing RF signals to travel into the attached devices.
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Jason Hills

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Thanks, that's exactly what we suspected after seeing the installation, great to have confirmation. Wanted to see if anybody has had first had experience. Could be intermod products generated inside the AP which won't be visible in the environment.
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Glyn

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Hi Scott,
In the scenario outlined above, are you able to describe what the behaviour of the download and upload (to the AP) data streams would be like please? I know of a case that fits the scenario where the upload data stream is one tenth what one would expect and is achieved off site. In this case shielded PoE cable was not used, nor were antenna filters or ferrite beads. Is there a way to measure and prove the existence of intermodal interference without the expense of re-running the PoE cable and buying antenna filters and ferrite beads? In other words, apart from re-wiring the site, is there a cheap way to build and prove a case for remedial work?
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Scott M., Sr. Support Engineer

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Hello Glyn,

I would try a small scale test to see if it's possible to mitigate the issue. If results are good, consider applying in more locations.
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Glyn

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Hi Scott,
thanks for that. That's what we have resolved to do; seems easier and quicker than measuring and proving intermod is a problem before acting.