[Imported] Interference between Trio 900 MHz radios and other radios in the same band

[sbeadle]

>>Message imported from previous forum - Category:Trio Data Radios<<
User: joelw, originally posted: 2018-10-17 18:46:52 Id:80
This is a re-posting from the obsoleted (October 2018) "Schneider Electric Telemetry & SCADA" forum.

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**_dvdsntndr:
We had problems with interference between two devices TRIO JR900, with equipmentfrom the same MMS range of 902 to 928MHz band with FHSS are about 30 metersdistant but still communication is interference. You know of some configurations to make something like a band pass filter or reducing overall speed?_**

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jweder:
If both radios are in the same 902-928 MHz range then it is not possible to prevent interference using bandpass filters. A horizontal spacing of 30 metres between the two antennas will provide about 58 dB of isolation. This normally should provide enough separation to prevent significant interference if both systems are running at 1 watt, and if both are frequency hopping systems. If one were a Direct Sequence spread spectrum radio then it would require greater separation.

Are BOTH systems **Trio** 900 MHz systems? If so, AND if both are Access Points, there is a feature built in to Trio radios called Multi Master Sync mode which can help eliminate interference. If however one radio (or both) is a Remote, or if one is not a Trio, then this mode cannot help. Multi Master Sync is discussed in the User Manual.

The best way to reduce interference between two systems on the same frequency band is to have vertical separation of the antennas, with NO horizontal separation. Eg one antenna directly above the other. This presumes both antennas are vertically polarized. Vertical separation is about 10x more effective than horizontal separation with vertically polarized antennas. A vertical separation of about 4 metres is usually all that's required. (again, one antenna directly above the other)

If the antennas cannot be moved to the same location (one above the other) then moving them as far apart horizontally as possible (with as much vertical separation as possible too) will help to some degree.

In Trio frequency hopping radios such as J Series and K Series you can set a few parameters which can improve system reliability under conditions of interference:

- Set the Hopping Interval as fast as possible eg 50ms
- Set the Data Retransmissions parameter in the Master to (eg) 3 or more
- Enable Force Retransmissions Across Separate Hops
- Ensure the Retries parameter is set high eg 9 or 10

Reducing the radio data rate in one or both radios would not likely help in this situation.