timing woes. help!

I am a little upset with Motorola right now but I am sure I only have myself to blame. We planned our network to connect our sites using 5.7 advantage equipment - and all our customers are 900 mhz canopy to the end user.

site “A” is in a metro area , 8 customers, 906 mhz. Timed via a CMM.

site “B” is in a rural area, 5.36 miles west and southwest of site “A”. There is a 5.7 AP here now being timed by a sync pipe (we used to have a 5.7 AP at site “A” but removed it so that is why both sites have gps timing).

Site “B” has the 5.7 AP and 2 900 mhz APs…on 120 sectors. North and west facing AP is on 906 mhz and South and east facing AP is on 919 mhz.

site “C” is 8.24 miles north and east of site “B” and is blocked from site “A” by terrain. It’s feeding from the 5.7 AP at site “B” and was receiving it’s sync from there as well.

After about 7 customer successfully installed, we started seeing clashing between the 919 panel at site “B” (facing oppsite this tower, 8.24 miles away) , and this tower, which is a 900 mhz omni on 919 mhz.

site “B” - 919 mhz has 21 customers
site “B” - 906 mhz has 15 customers. I believe we’ve moved 906 to 911 mhz now.

In an earlier configuration a month or so ago, we were timing the entire site “B” (the 2 900 mhz panels) using the timing pulse from a 5.7 ap at site “A” that was synced by the CMM. We took the timing pulse from the SM at site “B” and ran a timing cable from the SM to each AP.

When all the leaves fell this year, we had self interference issues between the 906 mhz panel at site “B” and site “A”.

I understand we can extend sync one jump using the equipment - this has not worked for us at all over about seven customers. I do not understand why.

Any advice?

We installed another sync pipe at site “C” tonight and all is well again but i’d still like to explain to our tribal council administrative group what is going on and why what i told them should work isn’t working.

jay fuller
cyber broadband inc

All of the 900’s are configured identically in every way? Any variances from one AP to another is enough to cause self interference.

- Max Range
- Control Slots
- Downlink Ratio

You mention 906, 911, and 919. There are only 3 non-overlapping channels at 906, 915, 924.

I would suggest putting Site B on 906 and 924, and Site C on 915 and confirm that all of the settings in all of the AP’s are identical.

Thanks Jerry…I will double check those settings - I know some of the max distances are off. (even with GPS timing they’re different, is that a problem?)
924 is pretty unusable around here due to paging around 929.


If all 3 AP parameters are the same, and the AP’s have GPS then you are in sync.

Change one parameter in the AP and the timing changes. You can have different max ranges, but you need to adjust one of the other parameters, usually downlink to get it back in sync.

Use the Frame Calulator in the radio under expanded stats. Instructions are in the operators manual.