900 SM's Loosing Connection

I am hoping I can get some general advice on a situation that has been driving me crazy for a while. Anything from general advice to specifics regarding the settings in the AP’s and SM’s would be appreciated.

Here is the situation:

First of all, we are in a a very rural, mountainous area, so in general I think our floor noise level is pretty good. This particular neighborhood is around the corner from a mountain range, so it is pretty isolated even from our own main tower. We are getting service to it by receiving a 5.2 signal from the tower and relaying the signal from a house that can see our tower and basically bending the signal 90 degrees around the corner to this neighborhood and broadcasting at 900. This house sits about 2 miles away from this neighborhood, on top of a hill, probably about 300’ above the neighborhood. So our AP is located in a pretty good location in terms of seeing this neighborhood. There are some trees surrounding this neighborhood, but nothing too bad.

- We are using a 900 AP with an external PCTEL MAXRAD MP8066XFPT (these were the standard antenna that was shipping with most Motorola 900 units)

- We are supplying service to 22 subscribers in this neighborhood and 2 subscribers in a neighborhood about 3 miles down the road.

- So the 22 subscribers are no more than 1.5 miles away from the AP. The other 2 are about 2 miles away.The houses are are close to each other. So the 22 SM’s are all in a neighborhood probably about 2 square miles.

Given the above setup, I would imagine that we have plenty of power with the exiting antenna to hit all subscribers. But what I am seeing is that occasionally a few of the SM’s just freak out and will loose connection and have a hell of a time registering. We have used different model SM’s (integrated/connectorized), different antennae, and we can not see any sort of pattern to why this happens. Sometimes I play around with the frequency on the AP and manage to get everyone back on. Other times, like right now, no matter what we do, we can not get the problem sites to register.

So at times we can go for weeks if not a coupe of months w/o any problem whatsoever, and then BAM, a few SM’ drop off. Jitter goes haywire, and we can not get hem to come back on. And usually after w few days, the will be all good again. keep in mind that the majority of the SM’s stay quite solid throughout this. It’s only 3 or 4 sites that start having problems.

So am I correct to assume that this is caused by interference? If so, is there a concern about interference from the SM’s on each other? Can the close proximity of the SM’s cause them to have problems? And if so, why would they work for weeks at a time, and then suddenly freak out?

I have read all the other posts that talk about interference from baby monitors and phones. We have looked into this, and there are definitely some possible issues there, but again, I have to go back to the point that this setup works for weeks at a time w/o any issues. People with baby monitors have them on everyday and their behavior does not change that much so suddenly.

Nothing we have seen indicates any sort of pattern. Majority of the SM’s are 900 integrated models. On the few problem sites we have tried everything from Stingers to yagis. Again, no consistency. One site was having problems, so we changed them from a connectorized to a yagi and everything was fine for a few weeks. Then they suddenly starting freaking out. We were at the end of our ropes, so we changed them back to an integrated model and suddenly they were getting better signal than they were with the yagi??? They were fine on this setup for about 6 weeks, and now suddenly they are falling off again.

Sorry for the lengthy post, but I am just hoping that someone has some light to shine on this. I am considering getting a better antenna for the AP, but is this really something I should be worried about at less than 2 miles away from the AP? Assuming the interference is from baby monitors and such, would a stronger antenna on the AP overpower these? Or should we concentrate on better antennae on the SM’s (although as stated above, there doe snot seem to be any consistency with whatever type of antenna we use).

Thank you.

are you using sync? if so try and switch to generate sync for a short time and see if that helps any. sometimes you can have a sync issue and nothing on the cmm or ap shows to be wrong and can cause problems with registering and re-regs.

nucoles wrote:
are you using sync? if so try and switch to generate sync for a short time and see if that helps any. sometimes you can have a sync issue and nothing on the cmm or ap shows to be wrong and can cause problems with registering and re-regs.

Thanks. I have the AP generating sync. There is really nothing else to sync to in this case. One AP, bunch of SM's. No CMM or anything else. So I am not sure if sync should be an issue.

Not to potentially change the subject here, but sync is one of those things that I am a little confused about. I was told repeatedly elsewhere in this forum and of course by Moto that EVERYTHING in my network should be synced. What I don't understand is why does a portion of my network (such as this) which has NO LOS to any other part of network, need to be synched to the other portions of the network? Isn't the point of sync so that radios do not step on each other? Well, so in this example, as I described, this neighborhood is around the mountain range with absolutely no LOS or NLOS to the tower or any other portion of our network. Its only link to the network is through a relay set up in the house that can see the tower on one side of the house, then we have wire running to the other side of the house, up a hill where we relay the signal 90 degrees behind the mountain range. That house receives 5.2 signal through an SM (which is synced to the tower) and transmits 900. So is syncing with the rest of the network an issue here?


with 900 it can be if someone else might possibly be using canopy or if you are using another 900 on another tower. if your 900 ap can “hear” another 900 then it should definitely be synced. otherwise shouldn;t be a problem. 900 does go a long ways in some cases one ap can see another 40 miles away depending on terrain and other variables in which case both your ap and the other should be synced as to not interfere with each other. 2.4 and 5.x obviously arent as much as issue considering the distance of the transmitted signal doesn’t go near as far as 900.

also have you done a spectrum analysis from the ap to see if there is any actual interference?

also does any of these “problem” sites have customers that use a cordless phone or baby monitor the transmits in 900mhz? we have had a few customers, especially the ones with baby monitors, that just wreak havoc on the SM and cause so much interference that they completely drop or sit and re-reg over and over again.