using 120 degree sectors for 90 degrees

Hello. My system is almost overloaded. Getting LOTS of overload on all 3 APs. These are 900mhz, one has 40 SMs on it, the others less than 35 each.

I have 3 Tiltik 120 degree antennas. I would like to add another AP and antenna to offload/balance out my situation for a little while.

Can I use 120s for 90s? I don’t want to have to invest in 4 90 degree antenna if I could use 4 120s instead. I know there would be some overlap, but the APs overlapping would be on different freqs to not cause problems (906,915,924).

Or, these have detachable side panels. I assume they are some kind of reflectors/barriers to restrict the signal to 120 degrees?. Can these be modified to make them transmit at 90 instead of 120?

Please forgive, I don’t know much about RF and antenna construction.

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or you could just get another 90 or 120 in the opposite polarization.

So your saying you don’t see a problem with this:

3 120’s - arranged 90 degrees apart and one 90?

Thank you.

No. Im saying leave your 3 120’s the way they are. And if the noise floor is clean enough in the opposite Polarization just at a 90 or 120 pointed in the direction of the biggest density of your customers.
3 120’s in HPOL running 906,915,924
1 90/120 in VPOL running whichever of the three it backs up too. you wont interfere to badly if at all because cross pol knocks off 20 db roughly

You don’t have to change pole if they are timed spaced correctly, V-pol 900 gear has to be much more spaced (antenna specs will tip you in on the distance) the H-pol hardware can be 5 or 6 ft apart and you can recycle the freq if you are timed. You would then rotate your frequency 1 position ex: north: 906 SW: 915 and SE: 924 on 1 group and the other N: 915 SW: 924 and SE: 906

Using 120s you will need to be very away of your back bleed (good front to back ratio is important here) your H beam width and your separation, you will have 60 degree of reverse overlap of your RF so you MUST BE outside of your backside bleed beam.

if your vertical beam width is 7 degrees with a 3.5 degree down tilt, your rear noise will be level with the antennas (what you want), if you are less tilted, the noise will be centered downward so you will need to increase the tilt on those antennas to help keep noise under control. And for separation, we keep antennas 3x their physical height part from each other when recycling freq. that’s not the proper way to calc, but it usually is a bit more than the calculated requirement

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I’m just wanting to fix this as cheaply as possible right now. I am still a small WISP, and the budget is tight. Someone said on DSLreports forums that I could just take off the side panels, and presto, they turn into 90 degree antennas.

Or, since I am using 906,915,924 on 3 120’s, if I could simply add in a 90 and re-aim each 120 so they are 90 apart, if I could make it work.

I know there would be freq overlap on the edges of the 120’s (I am getting that now with them 120 apart), but if they are still 8-9 channels apart, wouldn’t it work?

I am getting a LOT of overload packets on my APs.

There are many factors that can contribute to poor performance at 40 subs (which IMO is not heavily loaded).

Older software
- upgrade entire network to 9.4.2 if you have not already (it’s the best yet)

You may have congested spectrum which adding another AP will only compound. A Spectrum analysis is needed. If you are quick you can minimize downtime to about 5 minutes. I open three tabs on the browser so I can manage the AP’s quickly by switching from tab to tab.
- Switch all three AP’s to SM mode (stops all AP’s and SM’s from transmitting)
- Run all three SA’s at the same time
- Take a screen shot of each SA
- Post all three here

Next determine if SM’s are running too close to the noise floor
- Tools --> Link Status
- Look for SMs that are within about 6dB of the noise floor. These SM’s will exhibit poor performance
- Upgrade the antennas or relocate the SM for better LOS

Possible the AP’s are not configured for the best possible throughput. Please post your AP settings for
- Max distance
- Control Slots
- DL %
- SW version

Possible problem with SM QOS settings. Please post your typical SM
- Sustained Down
- Sustained Burst
- Sustained Up
- Sustained Down

If it is determined that you do need more capacity (which you will need at some point) I would recommend putting in one 2.4AP on an H-POL omni and move your LOS/Semi LOS and near customers to it to free up space on the 900’s. As you grow you can change out the 2.4 Omni to 3ea 120deg sectors which would support ~300 customers.

My entire network is on 9.3 currently. APs are P9, SMs are mix of P9 and P10.
Most SMs on one AP = 48

Max range = 14 miles
Dowlink data = 75%
Control slots = 2

I will post spectrum results later. I don’t think it will be any problem.

I have each SM set to 128kbps sustained up and down, 164000kbps (20MB) uplink and downlink burst, low priority up and down 20000kbps

I realize this seems a bit slow, but most of these folks have been using dial-up b/c that was previously all they could get. They are all happy for the most part.

I have 2 T1s total to work with right now. Tower is connected to T1s by Tranzeo PTP units at about 3 miles.
I actually just upgraded from one T1 to two, that seems to have taken care of my problems…

Bump up control slots to 4 - that’s where most of your overloads are coming from.

With 20M burst buckets everyone is virtually wide open. I’ll bet they’re happy…

I would do something like:
- Increase sustained to 128up x 512 down
- Reduce burst to 4000 (.5M) up and 8000 (1M) down

I think your network will breathe a little easier.

Actually this setup has worked fairly well for me. I had my single T1 maxed out with about 100 users on it with those settings. Now that I have 3MB, the usage is barely over a single T1, even during peak times.

I’ll try those settings out and monitor it for a while.

I don’t think I can go the 2.4 route. I have a competitor here who is running on that freq, however, they are just using an omni but they have probably 4 or 5 of them within about 8 miles of my 900 tower.

Thanks for the advice Jerry.

the overloads are due to contention on the uplink due to too few control slots.

Do you monitor utilization on the AP’s?

Is the competitor using VPOL or HPOL? Likely it’s VPOL leaving the door wide open for an HPOL 2.4 setup.

Alternately 5.x for your clear LOS customers will help take the load off the 900 AP’s.

Thanks again for the info Jerry. Nice to get information from someone who has BTDT.

I changed my time slots to 4. Am monitoring.

Any idea about these Tiltek 120 antennas and removing the side deflectors to turn them into 90s? I got that response from another similar forum.