Multiple BH´s in one location

I need to install 4 20 MB BH´s in one building. Each one on each side of the bulding. Anyone has any recomendations on this matter (sync pulse, frequencies, etc)

what gand? 2.4, 5.7, 5.2? are you using a cmm?
If you are using a cmm2 set all 4 to recieve from the timing port.
if you are using a CMMmicro set all 4 to recieve sync from the power port
if you are not using a cmm set one to generate sync and the other three to recieve sync at the timing port. build you a cable that ties pins 1 and 6 of the timing ports of all 4 together. all pin 1’s together and all pin 6’s together.
Make all 4 timing masters so they tx at the same time. Fire all 4 up and put them in slave mode. turn on the spectrum analyzer and look for interfearence. Pick two of the cleanest channels that are far enough apart from each other. put units back in master mode and set the north and south master’s to the same freq. set the east and west to the other freq. make sure all 4 units are getting sync on the status page. then go install other ends. good luck.

What would you recommend doing when you have 5 BH’s on a single 2.5" Mast with maybe a few feet seperating them elevation wise? We have put in a redundant/seperate link so all togther we have 2 BH’s going south to our Backbone, 2 BH’s (reflectors) going to the West, and 1 5.2 BH going north-east. We have 2 CMM-Micros, one has the West and South (backup) and the other CMM-Micro feeds the remaining.

Freq’s are:

Support told me we need to set our sites to where they are all Master or slaves.


I guess I dont quite understand the question. From what you are telling me it looks like you have done a pretty good job. You want to set the bh’s up just like a ap cluster. The ap cluster gives you 6 60 deg wedges. You probably could get away with alot more than 6 bh’s on a location. I noticed that you only stated that the 2 bh’s going west have reflectors is this correct? or do they all have them? I use reflectors on everything but ap’s. That turns that 60 deg wedge into a 6 deg wedge. It focuses the beam width down more. This helps out in alot of diffarent ways. It’s like taking a small water balloon in your hand and squeezing it the diameter gets smaller and the length gets longer. You get more gain, and further distance with the BH. Another advantage is when the bh is recieving it is only looking at a 6 deg chunk of the rf environment instead of a 60 deg one in turn less interfearence.

Does your backup stuff run all the time or will you have to turn them on if something fails?

Yes they all must be the same if they are the same band like 5.7 so they tx at the same time or rx at the same time. to get a good example of this log into one of your ap sites on the eithernet side turn one ap into an sm and enable spectrum analyzer mode. Leave all other ap’s alone. note the rf levels accross the spectrum. Now turn all the other ap’s off and note these levels and you will see how a transmitter will cover up a reciever when they are located at the same site.

The reason I say log into the ethernet side is i had a installer setting up a ap cluster and he put 5 ap’s up and 1 sm. When it was turned on the system overloaded and you couldn’t even ping a single module. It caused 6 sites to go down.

The reason we do not have reflectors on all but two is because the link is only 1-2 miles in distance. We are going to set all the BH’s to Masters, and their download/upload %'s the same. That way they are all tran/rec at the same time.

The backup/redundant link will also be running the entire time, on the spare CMM. Reason being, if one link goes down, it will be able to reroute itself. The network looks something like this…

14miles__________15 miles______Site E - 5.2 BH
Site A ----------- Site B ------------ Site C
…l- 2 Miles
…Site D

The original link starts at D and ends at A. Site D is where our backbone is. The redundant link is the same except that Site C bypasses Site B and goes straight to A. This is the longest link, being close to 30 miles. Site B is slightly to the south if you were to draw a straight line. So Site C has 2 5.7 BH’s (no dish, mounted 2 feet apart) going to Site D, 1 5.2 BH going to Site E, 1 5.7. BH going to Site B, and another going to Site A.

The only reason i suggesten that was we built a 180ft tower a mile away from my shop. At the shop I put up about 50ft of rohn 25 tower to mount all my antennas on. We are a motorola service center and i take care of all the 2-way radio repair for two counties. Anyway i needed a place to mount all my antennas. I was checking the canopy system one day and noticed that the sm at the shop that talks to the 180ft tower a mile away had a rssi of 900 and a jitter of 6. Idont remember what the recieve level was but that is what i pay atention to the most. For some reason i just felt that being that close they should be better so i started comparing with other sm,s in the area. The sm was working fine no re-reg, nothing in log file. At the time i felt like all levels were acceptable even link test. I told my installer one of these days when he got time to put a reflector on the sm at the shop. He looked at me funny and said it’s only a mile away. We got busy and it never got done. About a month later a customer calls me on a saturday morning and says she can’t log into the webmail server so i try from my house no luck so i start checking canopy links. The email server is at the shop. i can ping all the way to the ap at the tower but thats it I look at the sessions page and see the sm is not registered. it comes back up and has a re-reg count of 60 after having virtually none for 6 months. I go to the shop and install a reflector. rssi came up from 900 to 1570 jitter went from 6 to avg of 2 power level is -57. I rebooted the ap to reset the counters. typing this i just logged into the ap and it has been in session for 27 days and the re-reg on that sm is 3. So that is why now everything gets a reflector except the usual ap’s and 900.

I agree, it is a good idea to always use a reflector especially on BH, they act as a shield, and also help with self interference if you have your own equipment close by.

I’ve had to use reflectors on AP’s in the past to get out of tricky situations