Microwave Link frustration

[jmfirefighter20]

Hello All,

Hopefully I can pick the collective brain here to figure out an issue I'm having with two of my microwave links.

The first link is about 8.5 miles from my Water Tower to a Fire Tower on a hill. She's running in the 4.9 band and normally has an aggregate data rate in the 30-35 Mbps range. I've been able to get behind the dish and can see line of sight back to my Water Tower from the fire tower end of the link. There is a ridge with some trees about half way through the path, but I can still see the water tower fine from the level of the dish.

Second link is about 5 miles from the Fire Tower to a different Water Tower in another town. This one is running in the 5.8 band and normally runs in the 10 Mbps range. This one DOES have some trees in the way about 200 feet down the path, but they are deciduous trees and they haven't started leafing out yet. It's in works to get the trees trimmed this spring pending approval from the town.

What's occurring to BOTH links is random drops in data rate to CRAP. The first link will drop to 10ish Mbps, the second one will be lucky to hit 2 Mbps. This is of course wreaking havoc with things. Both dishes for the first link are inaccessible without tower climbing, and the second link is accessible only at the Fire Tower end. I've checked the dish alignment for the second link and eeked out a little more on the RSSI, but not much. The first link I cannot check.

It seems that the issue occurs randomly, but that it occurs to BOTH links at the same time. I usually get a "limited by the wireless conditions" message, but occasionally the first link will give me a "limited due to byte errors on the link" message. My signal strength ratio V/H for the first link was in the +20 range with the aggregate rate in the low teens.....about an hour ago the switch was flipped, I'm running at 32 Mbps with my strength ratio at -3 or so. The second link, also starting an hour ago, has had slowing increasing and fluctuating aggregate data rates.

Something changed an hour ago, but what? It's not really windy out today, and I've checked the spectrum management screen and didn't find anything I didn't expect. (For the first link on 4.9, we have a adjacent 4.9 path which causes interference on one channel.) I also would expect that interference would only cause an issue with one of the links, not both, unless the speed of the first link from my water tower to the fire tower can affect the speed of the second link.

When everything is running correctly, I'm getting what was predicted out of the LinkPlanner software.

I'm stumped. Anyone have anything to offer? Thanks in advance. I'll try to answer any questions to the best of my ability.

[tuckerm]

I'm a networking guy...so bear with me. What' getting pushed across the Microwave? Sounds like bursts of excessive traffic to me. If it's a link with network stuff on it, try running Wireshark on it to see what is happening when the links start to choke.

[jmfirefighter20]

I on the other hand am not a network guy, so bear with me as well!

We have IP traffic if I understand what's going on with my system. Our analog transmitters (all 4-wire) go into RAD IpMuxes on either end of their respective links. Our P25 Astro Quantars go through RAD SPS and FPS devices on either end. There are routers at each site as well which obviously routes all the traffic to the appropriate RAD or SPS/FPS for the system to work.

I probably got that wrong, but this part of the system is NOT my strong point. I understand what everything does to a point, but........now put me in front of a radio and I'm good all day......

[tuckerm]

If your links take such a hit like you are stating, I would be inclined to believe something is broadcasting traffic across your network. It's hard telling what it is. See: http://en.wikipedia.org/wiki/Broadcasting_(networking)

*Does it happen day and night?
*What else is on that network, just radio equip?
*What's changed? If this thing has just started to act up, what has changed in your network configuration?

[jmfirefighter20]

It happens day and night, sometimes for a few days on end, sometimes it's quiet for a few days.

Just the radio infrastructure equipment is on the network. There are two terminal PCs that allow login to the network: one from the radio room, and one from my office.

Nothing has changed recently except for the addition of the computer in the radio room. I'll try DCing that for a few days and see what happens. I'll leave wireshark running as well and see if anything pops up.

[tuckerm]

If it's a networking issue, Wireshark *should* see something.

The addition of the computer in the radio room...were there problems before you added that machine?

[Bill_G]

You didn't say what model of links you have, but the "limited by wireless conditions" and a VH ratio were a dead give away they are Canopy / Cambium PTP product.

Are these connectorized radios with external dish antennas? If so, you might be lucky enough to just have connector problems with the cables, or the mating connectors on the dish and/or radio. If you are unlucky, water crept past the not-so-water-tight seal of the two halves of the housing, and it is merrily destroying your radios from the inside out. If you are using integrated antennas, you could have water creeping into the panel antenna, and/or water getting past that not-so-water-tight seal.

So, are you feeling lucky?

I cannot explain why both are exhibiting the problem at the same time, but a V/H ratio that is far from the center is a good indicator of antenna and cable problems. I've had crews put these up, and then put their wrench on the connectors on the radio thinking they were tower bolts requiring lots of torque not realizing they are breaking the connector out of the housing in the process. Then we get plagued with problems like this until we can swap out the unit. Hopefully you have spares.

If you are using panel antennas instead of dishes, you may want to have someone check them for water encroachment. I've had raptors use them as perches. They are strong enough to bust the plastic, and let water in. Even big owls can break plastic that has had a few years in the sun. Kind of a common problem here.

[jmfirefighter20]

No, but the machine was in there for a while before the issues started.

Bill,

Both are Cambium PTP products....one is a PTP49600 and the other is a PTP58400 lite if I recall, I'm not at the office to confirm.....they are connectorized with external dishes. I'm not feeling very lucky, but it's really not going to be my problem if they fail because it wasn't my watch when they were ordered or installed! The budget isn't going to feel well, but that's the fault of those who refuse to establish a capital reserve fund for equipment failures, nor who have wanted to build any redundancy into the system, and I have no spares in my shop.

When it finally fails, I'll get to do the good ol' "told ya so" routine, shrug, and go back to my office while they pay though the nose to fix it. One of our other links just failed as I had mentioned in another thread and it was $5K to get it fixed...fortunately that was not out of my budget, but one of our local municipality's budget.

I am hoping that at least with the second link the trees are obstructing causing an issue rather than a hardware issue. I did look at the radio and the cabling on the accessible end and it looked fine, but there's no telling how it actually looks inside the unit.

I'm waiting to hear back from the climbers as to when they may be able to come out to check the alignments and hardware out before I start hauling out the $$$ guns.

[Bill_G]

I reread your first msg. Looks like only one has the V/H ratio change suddenly. That one is probably cable connectors. What kind of cable? LMR400 with crimp on connectors? If the line goes high (towards vertical) it's the horizontal cable broken on one end. If it goes down (towards horizontal), then it's the vertical cable on one end. You just gotta figure out which end with the push and tug test. Watch the vector errors. The end with the worst vector errors is probably the one with the failed cable.

Your link with sudden loss of throughput should have other indications as well, like low rsl, increased xmit pwr, increased path loss, and maybe a ratty looking vector error screen. If it too has bif swings in the V/H ratio, check the cables first. But, if V/H stays centered, and you cannot see any interference on the spectrum screen, then you may have to troubleshoot by substitution ... which you can't do without spares.

[jmfirefighter20]

Hi Bill,

Both links are acting how you describe them, however the V/H is all wayyyyy up when the throughput goes down, but comes back near center when everything is running well. I just had a thought pop in my head that perhaps the issue IS a cable, and maybe it's a heat/cooling issue? The cables up on the fire tower spend pretty much the whole day baking in the sun, and obviously at night or on chilly/windy days it gets pretty cold. We've had one of the coldest winters in recent history up here in New Hampshire. Food for thought.

[Bill_G]

Do both links originate on the same water tower? Is that your central point? Somehow I read they were miles apart.

If both go high, then both have problems with the horizontal path. The V/H screen is telling you there is more vertical signal than horizontal. When this happens, you should also have a ratty looking Vector Error screen. Reading that screen during a failure is like reading bricks during an earthquake, but one of the link ends is going to have a slightly better long term graph than the other. That's the end that's okay. But, there are only two ends to a link. Ultimately, it's a coin toss.

[jmfirefighter20]

Bill,

The common factor for both links is the Fire Tower. The first hop goes from my water tower to the fire tower, and the second hop goes from the same fire tower to another water tower.

If I take some screenshots of the diag plotter, would you look them over?

Thanks

[Bill_G]

Yeah. Send me an email through the board. I'll respond from my desk which will give you my addy to send the screenshots.

[RF_Burns]

Joshua,
Read my recent issues with PTP49600 equipment here:
http://batboard.batlabs.com/viewtopic.php?f=10&t=107550
My issues seem to be the case seal leaking and water gets inside. The links will go along fine then suddenly the H/V will go high or low (indicating a poor signal level in either Horizontal or Vertical) and the vector errors go crazy. Swapping out the bad end and everything is great again.... for a while. The hollow "O ring" seal around the case relaxes over time allowing water to seep in. I now have a spare I've sealed with Hylomar non-drying sealer. I'm hoping this will seal out the water, yet let me open the case in the future. Now that the weather is warming (slightly), we will be sealing all our PTP600 links before they go bad.