Walmart 900 Mhz interferece....coming to your area soon!

Be advised that Walmart stores everywhere are installing 900 Mhz radios at their stores to facilitate inventory tracking.

Freq range is 902-930 with “circular” polarization.

All my 900 SM’s within 1/4-1/2 mile experianced extreme jumps in jitter and loss of connectivity.

Spectrum analysis showed all freqs from 902-930 @ -39 DB’s at 1/4 mile in all directions.

Walmart is cooperating with us. They turned the system off and is working with us to find a solution.

If you find this interference in your area, contact the store manager to iniatiate cooperation with their RF Engineers.

we have a tower about 2 miles from our walmart as the crow flies and we’ve had higher jitter on 3 of our 19 customers in walmart’s direction (the other side of the tower on the other panel is fine). don’t know if it’s walmart yet. fyi. started about three weeks ago. we’re over in cullman.

Glad to know another user is nearby. How long have you been using Canopy? We have been up for a year, 15 AP’s and 202 SM’s.

According to the Walmart Engineer, they have been doing several start-ups in the past three weeks. Unusally high jitter was the first sign of the problem.

Take a connectorized SM with a Yagi antennae and drive around their parking lot. Look for a signal between -47 to -39 Db’s in all freqs between 902-930. Take a hard look around their loading docks. The antennae they use are inside the building, so don’t expect to see any on the building.

We turned the power way down on our AP’s in order to omit our signals during the search.

It only took about 20 minutes to determine the offender.

Notify store mgmt if you suspect Walmart to be the offender.
After we contacted the store Manager, they turned the system off within 1/2 hour and I received a call from one of their RFID Engineers stating that they would work with us.

He basically asked for one portion of the sprectrum. I agreed to keep all my customers in that area at 906. Allowing them to use the upper range.

We have not had any more interference from them since.

Good luck

seven towers and nearly 100 sms…but we’ve been doing this part time.
if it is walmart, it’s only affecting 5 or so of our customers…we have no more radios currently tho.

speaking of which…email me at if you could.
if you have some to spare…even a small quantity, we’d sure like to talk.
might benefit one another to come look at each other’s networks too since we’re so close.

-jay fuller
cyber broadband inc

We’ll do

we have been contacted by walmart today (actually monday, but we’ve been passed to some other folks) glad this part of the crisis is over…back to monitoring jitter numbers. :slight_smile:

I have an update.

Walmart has found some type of workaround for the interference caused by their RFID system.

I was contacted today by one of their Engineers. He ran a one hour test while we monitored the noise floor at their store.

We saw no increase above the noise floor.

According to this Engineer, they have lowered their power levels.

Somehow, the power stays very low until an inventory tag is "sensed."

Then the power increases until the tag is scanned and then the power level drops again.

This is their explanation.

However it works, the interference did not re-surface and none of my SM’s experianced any problems.

So Far so Good.

Reay Culp

Does anyone have a contact telephone number for the RFID people at Walmart? The interference just “popped” up in my area today and the manager at Walmart was less than helpful.

Did the Walmart Engineer call you?

He said he would shut the system down and contact you.

we were great until yesterday ourselves…apparently memorial day is a huge shopping day. we’ve had nonstop connectivity problems since about six last night. the walmart rfid number i was given is (479) 721-7131