900MHz Interference issues

We are having a hard time getting some clients to get stable connections out in the boonies through some trees, sometimes very few, over very short links. Session counts go into
the hundreds a day. There are NO other sources of background radio noise in these areas,
other clients work fine.

Is there a white paper on how to solve 900 Mhz jitter and session count issues?

Does grounding help using out door ethernet to an arrestor to a water pipe?

Do wire loops harm near the radio?

Do metal roofs or other TV like antennas scramble the signal?

Is it always jitter? The signals range from -70 to -50 db.

Is Fresnel a serious problem over low installations?

Thanks Homer

I’m more of an inside guy but here’s what I do know

hwsmith wrote:
Is there a white paper on how to solve 900 Mhz jitter and session count issues?


Best I can recall is the manuals on Cambium’s website. You’d think it would just be how to configure the equipment, etc, but there are a lot of implementation guidelines and even a little troubleshooting in there. High jitter and session counts with a good signal are almost always interference - the question is whether it’s external or self-inflicted.

hwsmith wrote:
Does grounding help using out door ethernet to an arrestor to a water pipe?


This won’t help you with interference but it is a very good practice and there may be certain grounding requirements in your area’s electrical code. I have no idea what they are up here in Canada, but I do hear of guys down in the states mentioning NEC requirements.

hwsmith wrote:
Do metal roofs or other TV like antennas scramble the signal?


Metal surfaces are the #1 enemy of wireless. 900 MHz bounces easily and penetrates a lot of things, where it will continue bouncing around. You may have luck detuning the SM (pointing it away from the AP slightly) or you may have to move it to another location.

hwsmith wrote:
Is it always jitter? The signals range from -70 to -50 db.


Not sure what you mean by this. Jitter is a representation of the unpredictable changes in a received signal, or a distortion rate if you prefer. Low jitter is indicative of no problems.

hwsmith wrote:
Is Fresnel a serious problem over low installations?


Depends on the link distance and how large the object is. 900 MHz usually behaves well with fresnel zone encroachments from “soft” objects like trees. But if you’re shooting right over the top of a steel barn you won’t have much success at all.

Thanks for your response.

My question about jitter was meant to ask if there are other kinds of
interference from non canopy sources, even raw 900Mhz in the same frequency band, or is
self interference the worst offender because the coding is the same. Is interference a problem because of mere energy or power in the same spectrum, or because of identical coding in the same spectrum?

My question about fresnel, is we are deploy in valleys and dales. Sometimes the source
is about 80 feet above the ground like a silo, and the client house is level with the base of the silo, but there
is a 40 foot hill between the house and the silo. One can SEE the silo top and the antennas from the install on the house, but the bottom part of the silo is blocked by raw land, thus I presume cutting off the bottom of the fresnel zone.

Is that going to be a problem?


Thanks Homer

Any interference will cause jitter.

As for your LOS/Fresnel questions, that’s beyond my knowledge. Our installers make extensive use of Radio Mobile to calculate that stuff. I believe Cambium has some tools as well to help plot links.