We have had several wireless networks at our plant in Illinois in service for a couple years now. The first time we've seen major drop-outs was during the snow blizzard a couple weeks ago.

The interesting thing is that it was NOT snow accumulation that caused the outage, it must have been the quantity of snow in the wind/air, because the fierce winds kept the field radios relatively free of snow accumulation (they're quite high up in elevation, about 180ft up).

The drop-out was on the battery powered field radios that were at a maximum of 250m from the gateway radio. All these radios have direct, visual line of sight to the gateway. These field radios are direct-sequencing technology. They all dropped out at the beginning of the storm and only resumed when the blizzard stopped.

The line powered (through a 24Vdc supply) radios that are full 1 watt output AND frequency hopping technology worked through the storm. This pair of receiver senders does not have visual line-of-sight.

The line-powered (through a 24Vdc supply) radios that are Modbus modems were in-service about 90% during the storm. These are supposed to be 1W, frequency hopping radios also.

Anyone else have any wireless observations during this winters' storms?

 

There's only so much water you can shoot through and ERP will be the bigger factor. Lower frequencies do better but that would be much lower, outside the band. If you go low enough, you can even talk to submarines:^)

Regards
cww

 

It may be something a simple as the water in snow is absorbing the wireless transmission.

William (Bill) L. Mostia, Jr. PE
Sr. Consultant
SIS-TECH Solutions, LP

Any information is provided on Caveat Emptor basis.

 

We are on the seashore on a finger of land projecting into the sea. On our 43 km 5.8 Ghz link which has about 12 db of fade margin, we can have complete loss during heavy rainfall. The link keeps working otherwise. CWW is right about water. Only thing is, the submarines listen in 10's of hz-khz range.

Regards,
Tomy Zacharia

 

....and of course the submarine comm is only running a meager 2 MW at 14-24 khz. A verrrry different world at VLF.

 

And you need many square miles for the antenna.

Regards
cww

 

Maybe that to high speed winds can shake your antennas and cause random misalignments between them. This is notorious in line of sight links. Links that do not rely on line of sight antennas tend to be robust against mechanical perturbations.

 

I'm trying to recall whether we've had winds like we've just experienced in this recent blizzard at other times. I honestly don't know.

The field instrument radios are 2.4GHz and their omni directional antennae are about 100mm (4 inches) high. The transmitter is rigidly (conventional transmitter mounting bracket) attached to the surrounding structural steel. The receiver's antenna is a higher gain omnidirectional, it's about 200mm (8 inches) high.

It could be that the structural steel resonated in the wind, but can a low audio frequency (300Hz) vibration misalign a 2.4GHz signal?

 

Omnidirectional antennas should be fairly tolerant of movement. It's the highly directional Yagis and reflector types that are sensitive to movement. That's the price for the gain they deliver

Regards
cww