Strong 900MHz dropping randomly

Hi Everyone,
I’ve started a small WISP in a heavily wooded rural area. I’ve got 5 customers so far all within 0.5 miles of my tower. I’ve got 3 900MHz APs on my tower. 2 of my customers, which have -60dB connections with jitter usually around 2, randomly drop their connections. They are on different APs and they don’t drop at the same time. When I check their radios, they have not rebooted and the AP does not increment the re-reg count, just the reg count. I’m guessing this is some sort of interference and since they are on different APs it seems like it’s at my end, but there’s nothing around and the 2 customers on the 3rd AP are working fine, as well as another one further away on the same AP as one of the ones with problems.

Any suggestions would be greatly appreciated. Thanks in advance!
Ryan

be sure they dont have 900mhz cordless phones or baby monitors. those are the most often types of interference we get.

thats the first thing i would check before going any further.

Are the AP’s in sync?
Do they all have the same configuration?
What antennas are you using on the AP and SM?
Have your read the manual?
Have you scoured this forum?

Jerry Richardson wrote:
Are the AP's in sync?
Do they all have the same configuration?
What antennas are you using on the AP and SM?
Have your read the manual?
Have you scoured this forum?


Thanks for the replies!

I've checked the phones, etc. at one location. They have a DECT phone which I think is OK. The other location just started dropping today and had been solid for 2 weeks with no drops at all. All the APs are in sync and using GPS. They all have the same config. I'm using SuperPass 70 degree sectos on the APs and 9dBi Yagis at both locations. Actually, the first one had an integrated SM and I figured it must have failed the link got so bad, so I just replaced it with the Yagi. Had no trouble locking in (they are actually only 0.3 miles from the tower thru some trees).

I have read the manual and the forum, but I'll go back and look again. I'll do some spectrum analysis this weekend and see if anything new turns up.

Thanks again,
Ryan

If you are going through trees, I recommend as much gain as you can get. One tree can be 9dB of loss when wet. You can always turn down the Tx power on the SM if necessary.

I assume you are using this antenna: SPHDB24S. Superpass are not null-filled so you are going to have inconsistent results from customer to customer. At one location a 9dB will work, in other locations the same distance it might take a 13 or 17dB antenna.

Jerry Richardson wrote:
If you are going through trees, I recommend as much gain as you can get. One tree can be 9dB of loss when wet. You can always turn down the Tx power on the SM if necessary.

I assume you are using this antenna: SPHDB24S. Superpass are not null-filled so you are going to have inconsistent results from customer to customer. At one location a 9dB will work, in other locations the same distance it might take a 13 or 17dB antenna.


I'm going thru lots of trees. Maybe I'll try more gain, but they've had good links, even with the rain last week. It's cold now and we had a touch of snow, so maybe... I think the Superpass antennas might be the SPHDC4S. Thanks for the advice about null-filled antennas. I didn't know that.

Ryan

Well, the connections have been solid since yesterday afternoon. One is up to -55dB, the other around -60dB, jitter 2 to 3 and not varying. I guess I’ll keep an eye on them for now. I have another guy 1.5 miles out that I’m having trouble getting much of a signal to. I’ve got an M2 17dB yagi that I’m going to try this weekend. He’s got aluminum siding and some power lines in the way, so I’m guessing that’s not helping.

Just curious: on the Session Status page on the AP, what is it listing for power levels and what is your noise floor?

wifiguy wrote:
Just curious: on the Session Status page on the AP, what is it listing for power levels and what is your noise floor?


OK, I finally got back to this. I turned all 3 of my APs (which are GPS synced) into SMs and did spectrum analysis. Everything was at -85 or below except 924. There is another WISP using Canopy 900 in my 924 direction and we've made sure we're synced and have the same setup. But I was reading about -65 from their AP. When these customers work well, their signal is typically at -60 or little better. Dropouts seem to occur if their signal gets above -60. Is there more that I have to do to get things to play better with this other WISP? One other customer on 915 seems to have similar problems and I see the 924 on that AP as well, although lower.

Thanks again for all the help,
Ryan

i have had this same problem customer had 6.0 Dect phone
nothing at all on 900Mhz (scan her house)
had a power lvl of -55 jitter 2
and 900 re-regs
tryd new cable new antenna and new firmware none of that help’t
finaly replaced the P10 radio with a new P10 with 9x firmware
and works perfect now
…so you might want to try and change the radio before you give up

Well, I upgraded the AP and the SM to version 9. Same problem exists. The signal will swing 10dB slowly over 2 hours or so and when it hits -65 it starts dropping. I switch the AP frequency from 924 to 906 but the same problem occurs there. When the SM is connected, I did a remote spectrum. The SM can see the 906 and 915 APs so those are about -60 or so but 924 is at -80. Doesn’t make any sense. I don’t understand how the signal can change so much even with trees in the way over such a short distance and I don’t understand why it drops at -65. Anything else to try?

Thanks,
Ryan

Hey rpmiller,

Are you using Prizm?
Is your network flat or Routed?
What kind of trees are you going through?
Where are you located?

Hi,
No Prizm. I’m using a Mikrotik router with PPPoE authentication,but the problem is with the air link between the SM and the AP. The trees are tall pine trees. Located in Michigan.

Thanks,
Ryan

The signal strengths you mention, are they from the SM or from the AP’s sessions page?

We also have a lot of pine trees here is Alabama. We had to go to 17 Db gain M2inc yagi’s.

The problem seemed to be that the SM’s could see the AP’s OK but the AP’s had a hard time seeing the SM’s when shooting through any trees.

Reay

The levels are at the SM although the AP is about the same and changes with it. I can understand having trouble with trees, but .2 miles - I can see the lights on their garage thru the trees! And why does it change so dramatically.

On another note, I discovered that Syncpipe has a firmware error that prevents it from populating the GPS fields with the new V9 software. It seems to still sync though. Can I use PPPoE with a V9 SM and a V8.2.7 AP? I normally use PPPoE from a router, but it would be nice to not have to include one every time.

Thanks,
Ryan

Was this problem ever resolved? I am seeing this exact same behavior with a new 5.7 tower where close-in clients are dropping link and immediately registering again, usually with a slightly different air delay value. 3 5750APs, P10, GPS sync over power, -65ish at AP from each SM, -50ish at SM from AP, less than 1/2 mile distance, good LOS. Spectrum looks good at both the APs and the SMs.

Not really resolved. I installed a higher gain antenna so it happens less often. The only think I can think of that causes the signal to swing so much is that they are surrounded by tall pine trees. I think the trunks cause big problems. Also, their DSS satellite dish is sort of in front of the antenna (although mounted below on the ground). I’ve had trouble with the dishes for my 900MHz radios. I think the LNBs must emit a lot of noise.

But if you have LOS, that doesn’t really fit with my scenario.

One thing we have noticed is that when using 900mhz. If the obstructions are close to the antenna, we tend to get a fair bit of reflection in signal from the obstruction (usually trees and pines even more so We’re even in michigan too).

This reflection presents itself as multipath interference. Which shows in large fluctuations in RF power & RSSI. If you have headphones for your canopy. You’ll hear it right away.

The solution for us generally has been to switch to a wide beamwidth client antenna, ie:panel and aim slightly off direction until the signal stabilizes. Or to use a yagi and add large ammounts of uptilt or downtilt and use the side lobes of the antenna.
Thus keeping the reflecting signal from having a large impact on the signal quality.

Hope that might help you

Hi

I am not sure what polarity are you using but in the dense obstructions scenario (tree like) I would go only for horizontal.
Have you done the spectrum scan with all APs turned either of or even better configured as an SMs for time being?

Let us know the results


Jiri C.