900 MHZ Backhaul optimization?

Hi all,
I am currnetly using an AP and SM as a backhaul unit. I have 2 13 DBI yagis on both ends. 1 SM is all that is connected to the AP. The link is 4.81 miles according to the Web Interface of the SM.

Any recommednations on what I can do to optimize this link? I am using hardware scheduling, 0 control slots, and transmit frame spreading disabled.

Thanks in advance,

what makes you think it is not good? Could you be more specific?

It’s good, just only passes about a 1/2 meg of traffic at the moment. As it gets more and more loaded I don’t want to have to worry about things then. I would rather get it optimized before any problems arise.


You should be able to get 3M/1M out of that link. My first suspicion is too much gain.

Can you take screen shots of the SM and AP status and config screens, post them on a server, and then provide a link to them here?


The above is the AP


This is the SM

After doing some tests I have found my download from the SM side is over a meg. Howeverm upload is like 300k.

  1. You may want to adjust the Downlink Data % to a lower number. Are you looking for equal uplink/downlink throughputs?

    2. Also enabling 2X mode will improve throughputs to SM.

    3. Improve the signal between the two units. -78dBm is a little on the low side.

    4. Reducing the Max RAnge in the AP may also improve throughputs.


My first suspicion was incorrect.

You do not have enough gain. The AP is only seeing -80dB of of signal from the SM (read from the AP sessions page) and the SM is only seeing -78dB of signal from the AP (read from the SM status page).

You have 2 choices
1. Elevate the AP and SM more to try and reduce the amount of foliage between the radios
2. More gain. Since you are at 13dB you can still bump up to 18dB, this will increase your margin by 10dB which should do the trick. No guarantees though :wink:


If you are going through any clutter, in other words, not strictly line-of-sight, minimally get to -60s in dBm. Change polarization if necessary. Next, decide what direction you want the most throughput. Next, as stated, make link distance next nearest integer of mileage, i.e. for 4.8mi, 5mi link distance. Absolutely try to get 100/100 linktest percentages. If you cant get 100/100 where you have antennas, move them where you can. Sometimes not a great change in position will yield great improvement in linktest percentages. Next, run continuous pings to make sure that you have stable ping times, i.e. not all over the road. If you are in a location to hear other 900 Canopy, use CMM to eliminate interference. If you want max throughput in one direction, dont be afraid of going higher than 75% on downstream, using 2x of course, will yield you surprisingly good throughput. 4down/.5up isnt bad for a lot of traditional surfing user environments.
Thats enough…

Jerry Richardson wrote:


I have a marginal signal at my house (80dbm) with a PacWireless 13dbi yagi. Would that 18dbi yagi make a significant difference?

Also, found same yagi for 74.95 and cheaper shipping (for me anyway) at http://www.echotechwireless.com/Product … 8&CartID=1