Nortel T7406 Static

[JTNortel]

I just bought a Nortel T7406 system the other day, and found that when I hooked it up, there is a terrible static noise on the handset. The caller on the other end hears just fine, but the audio on the T7406 hisses and crackles. It also shows the antenna at the bottom, but no bars like a cell phone would, is there suppose to be bars? It doesn’t mater how close you are to the base, or what the dip switches are set to, there is static on the receiving end, everything else works fine, it pages crystal clear. Can anyone help me?

 

[JTNortel]

I took the phone to my church who also uses a Nortel KSU and found that it works clearly there, I guess that there is some kind of interference in the 900MHz range here that they don't have there. I cant think of what could be broadcasting in that freq. range in this residential area, any ideas?

 

[misseditbythatmuch]

I recall that there are dip switches on the base that define either 902 to 915 or 915.1 to 928 as the frequency range.

Have you tried both ranges to see if the interference is more prevalent at one or the other ?

I think the dip switch was a 1-2-3 deal where looking at the base held level and from the rear, down-up-down was upper band and down-down-up was lower band.

Also, did you check the antenna connection ?

 

[JTNortel]

Thanks for your response, I have tried both upper and lower freq. bands, both have the same amount of interference. I have unplugged all RF devices that I can think of, wireless routers, wireless mouse, cell phones ect. I have moved the base to different locations, even tried it outside; It seems that the interference is escalated dramatically in the late night hours (10:00pm-4:00am). it's frustrating because now I know it's not a defect of the phone or the base since it worked 100% fine at the church. I don't know about the antenna connection though, it looks like it is permanently attached to both the base and the phone; if there is something I am missing I would greatly appreciate any help.

 

[misseditbythatmuch]

My longshot guess, maybe a neighbor has a new addition to the family? If you are in a residential area with low energy broad spectrum impact on the 900 mhz range peaking at night, I might guess at an older baby monitor (maybe gets moved to the baby's upstair bedroom when mom and dad go to bed and shut off when mom wakes dad up to do the first feeding ?!-- and then maybe get moved downstairs when the baby is in the playpen) There are so many 900 Mhz devices ranging from network devices, analog cordless phones, water and electric utility SCADA devices, and so forth.

If you have a helper, try placing a call and when your helper hears interference have him/her rate it and try moving an improvised signal sheild around the base to see if you can find a direction on the source of the noise (maybe a good ground wire and a medium to large aluminum foil "sail"). An imprecise science I admit, but it may yield a rough direction of the noise source like narrow you down to one point of the compass. Helper needs to move to, so that the foil does not come in line with the handset. Unfortunately, the handset will also be influenced by the interference, so it will kind of be an exercise like the squirrel chasing around the tree.

I admit up front this is a rough guess turned lab experiment.

 

[curlycord]

Maybe try a sheilded telephone cable going to the base station too, sometimes the cable pickup this up.

 

[RikRodgers]

Try the DIP's first. The 7406's frequency hop, so it's unlikely (but not impossible) to pick up too much noise from other 900MHz devices.

You might want to take a close look at the antenna on the handset, too. We installed one a couple of years ago that seemed to cut out all the time. After a couple of service calls, I discovered the antenna on the handset we ordered didn't have a conductor in it!

Ordered a new one, all better. You might want to see if you can borrow a handset from your church to see if the trouble continues.

 

[JTNortel]

Thanks for your suggestions, I opened up the handset and saw a silver cable connecting the antenna to the board so I don’t think that is the problem, again the strange thing is that it is only static sounding on the receiving end of the phone, if I call another set or dial out on one of the lines, the person I am talking to hears me just fine, it just sounds awful on my end, which I find strange. It also has no problem with range, at least 200 feet of range, so whatever is going on doesn’t seem to affect the range, the audio sent from the phone, or the connection to the KSU. (Page, voice call, transfer all work well) It doesn’t make any difference on the dip switch position either; it operates the same on both settings. Very strange indeed, looks like the church might be getting a free cordless phone to add to their system. :-(