New 900Mhz Link

Here it is, we have installed on our building (240’ AGL) the tallest building in the area and AP cluster consiting if 3 2.4Advantage and 2 900Advantage APs all are connected to a CMMmicro the second 900 is serving a different site about 2 miles apart. They both have integrated antenna’s.

The problem is this one AP is connecting to its SM about 2 miles just fine, clear LOS from both ends. The second AP is covering a larger range (both APs set to 10 miles). We can see to the customer location roof from our AP site, so we went to install the SM (integrated antenna) at about 10’ off of a large warehouse roof, all metal. What we got was interesting, the SM would show synching, then registering, then scanning. it never would complete a registration. We are exactly 7.7 miles as the crow flies. When the SM showed a “registering” action it would show the distance as either 10.03 miles if we had the AP set to 10 miles and if we changed the APs to 12 miles it would then show 12.03 miles. We are on a large metal roof which I suspect as a probem or not high enough, and we are right next to an airport as well.

What we thought we would do is to take the mast up another 10’ and then try the 900 again if that did not work we would then install a 2.4SM with reflector and see it woud had better success. Any insight would be great.


Don’t worry about it saying 12.03 miles… or just slightly over your max range setting…that is normal.

You are dealing with two issues

Airports = high power 900MHz radios.
Metal Building = large collector of RF energy

If you are trying to fire over the roof of the building that is a problem. Move the radio to the end of the building.

Thanks for the input, the building at its peak (slight gable roof, is about 30’) which if we had another 20’ max since the airport is nextdoor, and we cannot go more the 20’above the tree line, should that be enough? We are going to take a telescope onto the roof (been using a spotting scope) of our building to hopefully get a more detailed look from the AP side at the roof line so that we can locate a point of reference from the AP side since we can see the roof. From the SM side we cannot get up high enough to see the top of our building.

We will move the SM to the edge of the building and give that a try, what are your thoughts on using a 2.4SM with reflector?


There is alot of RF hash around airports. 2.4GHz is more fragile than 900MHz so I would probablay stay with the 900.

You are probably right to elevate the antenna. I have a customer in a metal hanger on the far side of an airport. I noticed that when the antenna was just above the roof line it would not work, but 6’ higher it worked better. I finally put it on a non-penetrating roof mount with the antenna at about 5’.


Jerry, your points are good but I think this is pretty obviously the 900mhz registration bug.

GPE, read my post at … php?t=1938 ; our WISP was having problems in many places on our 900mhz network, SMs with even excellent signal (-60 / 1) wouldn’t register before a long time; they would just keep scanning/syncing/registering for minutes or hours until
they got a connection. No interference around that i saw. When they were “registering”, the distance was always reported as 20.05 miles wherever the SM was (our max distance was 20 miles I think). So the continuous cycles + wierd distance readings make me think you have the same problem as us.
upgrading to 8.0 beta software didn’t help. But when we turned encryption
off at the AP the problem went away. I recommend trying that.

You are referring to Airlink Security?

I haven’t seen this, but I only have about 25 users per AP right now. How many SM’s do you have registered?

I will look at that and let you know what we get. thank you all for your feedback



We are still having issues with this link, the SM with intgrated antenna, just scans, synchs, and registering and never completes the registration, we had gone up higher and moved to the edge of the building, diabled encryption etc. I think an eternal stronger

I have ordered a Connectorized SM and have posted another post to see which high gain antennas you guys use and where you them from

As always you helo is much appreciated

The downtown side is at 240’ AGL, and the warehouse next to the airport is roughly 50’ AGL. I have Los from the 240’ Downtown side but do not have visual site from the warehouse side. At least not from the roof of the warehouse.

I have a Google file that I could send to you by email that will allow you to use Google to see my shot and provide input.


i to am experiencing some what the same thing.

i have several radios that are registering and then getting good rssi and jitter when installed and good link tests.

then all of a sudden they drop and try to re register and do register with good numbers but when you try a link test is says no session currently active.

then immediately will re reg again.

this is a remote location so i am assuming it is a very low noise level area.

i have been using the latest software and hardware sched.

very strange. we have the encryption turned off.

when i test out in the open with clear view it is 100 x 100 so i am assuming it is the trees.

we are using 13 db yaggis and will be moving up to 17 db yaggis and may be stack them to see what happens.

but i do feel your pain…
nothing worse than installing and then having problems right away.

You are right tooslow, problems out of the gate are difinitly no fun, I have ordered a conectorzed SM and three different yagis, a 13dbi, 15dbi and a 17dbi. I would install a grid dish, but we are installing on a telescoping mast at about 20’ above the warhouse, and I think that would be too big and cumbersome on the mast. We should know middle of next week once everything gets here

Thanks again for your input


My situation seems similar. The connectorized 900 sm w/12dbi yagi has great signal strength but has major difficulty registering. DES is turned off. I’ve changed channels trying to eliminate possibility of interference. This does not help. When it finally does register the pages are very slow and link test won’t work. Last night the SM was working great but today it is back to bad again. Maybe Canopy support can get in on this one?

I’m experiencing the same problem with one of my customers. Worked great for 2-3 months and now is failing and can’t resgister. Jitter is 1-2, rssi levels are 1600 -60dbm…All looking good but won’t register.

I am still having a problem here, scanning,synching, registering and so on. It never registers, the shot is 7.7 miles and from the AP side I can see the SM site but I cannot see the AP site from the SM location. I am just hoping we have an alignment problem, I have connectorized and integrated SMs and I now have the right cable to make an integrated 900Mhz a connectorized version. At least for testing. If this does not work then does any know if I can shoot 1.8 miles mostly through trees to another tower sitr we are building. no LOS at all.


I have found that removing all frequencies but the one you require helps. Or look at the spectrum analyser and try a new frequency which has the least amount of noise. Someone could have lit a paging terminal or another 900 site and this is interfering.