J
Hey all, i am having trouble communicating with a remote site, and I'm about out of ideas for how to fix it. Hopefully yall can give me some suggestions.
A little background, I work for a system integrator in TX (what accent? i dont have an accent.). We do turn-key systems, and then a large part of my job is servicing those systems if/when they have problems down the road. In this case, we are dealing with a water plant my predecessors put in almost 10 years ago. They pump out of a river appx 2.3 miles away from the plant. The communication link worked fine for about 10 years, but about a month ago, they started having communication problems. It started out where they would only have problems a couple of hours a day. Then they'd have comm fails all day, but it would work at night. Now they have a comm fail all day and all night.
I'll try to just throw as much info at yall as i can think of and see if any of it sparks an idea.
The System:
-There are about 10 sites around town. All of them except the river station have 99%+ valid polls.
-The radios are MDS 9300s (and probably some 9310s)
-they use the 900 MHz unliscensed spread spectrum band. frequency hoppers and all that jazz.
-The polling is done from a computer running Lookout SCADA software
-The RTUs are TI435 (which was bought out by siemans, which was bought out by PLC direct, but basically its the koyo processor and we can get replacement parts from automationdirect.com)
-We are using modbus protocol and the radio is connected to a MB slave card in the PLC rack. (f4slv-mb is the new part#)
I have double checked the alignment of the antenna, it was off by about 10 degrees, but repointing it didn't help.
I am pretty familiar with MDS radios, esp the 9800s, but a lot of my favorite commands are not available with the 9300s. (like rssi, zone data, snr).
the lights on the front of the radio indicate it is seeing a good carrier signal from the master, and it is recieving and sending data. the MB slv card is also recieving and sending data on a regular basis, but back at the plant, they show no responses.
i have already tried replacing both the radio and the MB card.
I checked for reflected power (to see if the antenna installation was OK), and I had rather interesting results. First of all, it was only putting out .5 watts (BTW, the spare radio was set up the same way) and second, the needle did not even twitch when i switched it to reverse power. Granted, my meter's lowest setting is 5 watts (dont get me going on this one, i told my boss we wanted the MAX range to be 5 watts, cause we work on low power stuff, but instead i got one that goes up to like 500 watts! WTF, i aint touching a 500 watt system with someone elses 10 ft wooden pole!), but i've never seen one that didn't even make the needle twitch. Theoretically, i guess this means i have a perfectly tuned antenna, but i have trouble beleiving this to be the case on a 10 yr old installation, and frankly, my predecessors who put this up knew diddly about radio systems back then. I forgot to check, but I'd be surprised if the connectors outside the building were even wrapped. I went ahead and adjusted r69 on the radio until it was putting out a watt (actually i left it at about .9 watts just to be on the safe side) So, question 1 for any radio gurus out there, if you get zilch on the rev power, does that mean your antenna is ideal? Or are there other possibilities?
>From watching the lights, i think the RTU is seeing the poll and answering, but the master is just not seeing its response. I have honestly never had a communication link that worked one way and totally crapped out the other way. There were a few times when i *thought* this was happening, but it always turned out to be something else. Like a bad transmitter, or the setup was wrong. I was really hoping that turning the power up would do some good, but it did not. has anyone else seen something like this?
Right now, I am leaning towards saying the problem is interference, but without a service monitor of any kind, i dont know a good way to test this theory. And saying that its intereference does not fix it. There is another plant within sight of the River PS, and they have a big omni antenna, so i am planning on contacting them and at least finding out what kind of telemetry system they have and how long its been up. Maybe I'll get lucky and they will have a bonafide guru around with a service monitor and everything.
thanks for the help
-jeff (i hope there's no char limit on posts)
A little background, I work for a system integrator in TX (what accent? i dont have an accent.). We do turn-key systems, and then a large part of my job is servicing those systems if/when they have problems down the road. In this case, we are dealing with a water plant my predecessors put in almost 10 years ago. They pump out of a river appx 2.3 miles away from the plant. The communication link worked fine for about 10 years, but about a month ago, they started having communication problems. It started out where they would only have problems a couple of hours a day. Then they'd have comm fails all day, but it would work at night. Now they have a comm fail all day and all night.
I'll try to just throw as much info at yall as i can think of and see if any of it sparks an idea.
The System:
-There are about 10 sites around town. All of them except the river station have 99%+ valid polls.
-The radios are MDS 9300s (and probably some 9310s)
-they use the 900 MHz unliscensed spread spectrum band. frequency hoppers and all that jazz.
-The polling is done from a computer running Lookout SCADA software
-The RTUs are TI435 (which was bought out by siemans, which was bought out by PLC direct, but basically its the koyo processor and we can get replacement parts from automationdirect.com)
-We are using modbus protocol and the radio is connected to a MB slave card in the PLC rack. (f4slv-mb is the new part#)
I have double checked the alignment of the antenna, it was off by about 10 degrees, but repointing it didn't help.
I am pretty familiar with MDS radios, esp the 9800s, but a lot of my favorite commands are not available with the 9300s. (like rssi, zone data, snr).
the lights on the front of the radio indicate it is seeing a good carrier signal from the master, and it is recieving and sending data. the MB slv card is also recieving and sending data on a regular basis, but back at the plant, they show no responses.
i have already tried replacing both the radio and the MB card.
I checked for reflected power (to see if the antenna installation was OK), and I had rather interesting results. First of all, it was only putting out .5 watts (BTW, the spare radio was set up the same way) and second, the needle did not even twitch when i switched it to reverse power. Granted, my meter's lowest setting is 5 watts (dont get me going on this one, i told my boss we wanted the MAX range to be 5 watts, cause we work on low power stuff, but instead i got one that goes up to like 500 watts! WTF, i aint touching a 500 watt system with someone elses 10 ft wooden pole!), but i've never seen one that didn't even make the needle twitch. Theoretically, i guess this means i have a perfectly tuned antenna, but i have trouble beleiving this to be the case on a 10 yr old installation, and frankly, my predecessors who put this up knew diddly about radio systems back then. I forgot to check, but I'd be surprised if the connectors outside the building were even wrapped. I went ahead and adjusted r69 on the radio until it was putting out a watt (actually i left it at about .9 watts just to be on the safe side) So, question 1 for any radio gurus out there, if you get zilch on the rev power, does that mean your antenna is ideal? Or are there other possibilities?
>From watching the lights, i think the RTU is seeing the poll and answering, but the master is just not seeing its response. I have honestly never had a communication link that worked one way and totally crapped out the other way. There were a few times when i *thought* this was happening, but it always turned out to be something else. Like a bad transmitter, or the setup was wrong. I was really hoping that turning the power up would do some good, but it did not. has anyone else seen something like this?
Right now, I am leaning towards saying the problem is interference, but without a service monitor of any kind, i dont know a good way to test this theory. And saying that its intereference does not fix it. There is another plant within sight of the River PS, and they have a big omni antenna, so i am planning on contacting them and at least finding out what kind of telemetry system they have and how long its been up. Maybe I'll get lucky and they will have a bonafide guru around with a service monitor and everything.
thanks for the help
-jeff (i hope there's no char limit on posts)