Sync Witout CMM

I have a router at my office and a tower. On that tower I feed the Internet to a 5.7 BHM and a 900 AP. The BHM feeds a BHS to big tower. On the tower is a 900 AP. The two towers are about 4 miles apart.

My question: Do I need a CMM or can one of the devices generate the sync pulse for all devices? Can I connect the AP and BHS with a sync cable and connect the BHM and AP with a synce cable and send the pulse over the BH air link for all devices to be in sync?


You don’t need the CMM. The two devices are in different frequency bands.

2 900AP’s will see and affect each other for as much as 10 miles. At 4 miles you definitely need to have them sync’d.

You can’t use the remote AP method because the sync signal is not present on the first AP’s RJ11 port.

The solution would be to use a SyncPipe at the first tower to feed sync to the first 900AP and the BH master (Receive on Timing Port). You will need to make a splitter.

At the remote tower you can take the sync from the BH Slave and feed it to the 900AP via the RJ11 by connecting pins 1, 2, 3, and 6 from the BHS to the AP (Receive on Timin Port). Then both towers will be in sync. Cost is pretty low - about 150 bucks.

Is the splitter just a Y cable with RJ11 plugs on all three ends?

pins 1, 2, 3, and 6

Is this a straight thru cable? Pins 1,2,3 and 6 are the same on both ends?

Thanks for the info Jerry

Yes, use scotch locks to make the splice pin to pin. I think there is room in the sync pipe for the splice.

Can I plug the cable into the AP & BHS and leave the AP to generate sync until I get the SyncPipe on the other tower? Then turn it on to get sync on timing port?

As far as I know you cannot pass the sync from an AP to a BHM or vice-versa, however I have not actually tested this.

You could test it by connecting 1, 2, 3, and 6 from the AP to the BHM and have the AP generate sync. Set the BHM to receive on Timing Port and see if it gets the sync. If it does, then the BHM will pass the sync to the the BHS which you could carry to the other AP.

If this works, then everything will be in sync and the sync pipe would not be necessary.

The way sync propagates across BH’s is from Master to Slave.

Generating Sync at an AP and connecting it to a BHS does not do anything for you as that sync is not going to be propagated from the BHS to the BHM.

Will this work?

Tower 1 has an AP and BHM and tower 2 has a BHS and AP. Tower 1 is the main one with Internet feeding the AP & BHM from my router. Tower 2 is being fed from the BHM. I’m going to order the SyncPipe this week. My climber is going up tower 2 today which is 317’ to do some falling ice repair. Can he connect the sync cable between the AP & BHS now before the SyncPipe is setup on tower 1? When the SyncPipe is setup on tower 1, do I then just connect the BHM & AP with the splitter and change both APs on both towers to Receive On Timing Port? I just want to make sure connecting the AP & BHS with the cable before getting the syncpipe in won’t hurt anything.

Yes, not a problem.