CMM Issues

We’ve been having a problem with a CMM losing sates and losing sync. We thought it was the cable so we replaced it with a 15’ lmr400 cable and it seem to work for 3 days then it started the same problem. It will hold 5 sates then start holding less and less then it just loses sync, any where from 30 minutes to 4 hours it stay down then it will start picking sates back up and it will be fine for 12 to 20 hours then start it over again. We’ve upgraded the firmware to 2.2 build 2. We have a second CMM on a different mountain top that seems to lose sates down to 1 sate but never loses sync, but when the first CMM loses sync the second will be at its lowest locked sates. Were located at the top of Idaho 30 miles south of the Canadian border. We have approx 300 clients and I’m running mostly 900mhz system. I have a UPS at the sites that I can turn off and on the power to the CMM, microtek and our backhauls and when I reset the CMM it seems to pick up 1 or 2 sates then starts to run ok for awhile. I know this is long winded, but does anyone have any ideas or have come across this before??

By sates I think you mean satellites?

Have you verified that your CMM antenna is 100% level with the earth, and straight up and down, and can see to the south?

Are you running the coax from the antenna into a Polyphaser or other type of coaxial protector?

Yes I mean Satellites, sorry!

The GPS antenna has been on a 140’ tower about 100’ up and was connected to a 15’ lmr195 for 3 years and no issues now it’s acting up. We checked when we replaced the cable with the lmr400 cable and it looked fine hasn’t moved.

I’m not using any cable protector. The cable is by itself going from 1 leg of the tower to the other and it is pointing south.

Probably the easiest thing to do is to replace the GPS antenna. If that does not fix it, try the CMM.

Those antennas are active units, so maybe the electronics in the antenna or the electronics in the CMM are shot.

FWIW, I only use LMR400 for my CMM to GPS antenna feeds and I do not have issues.

amd phreak wrote:
Probably the easiest thing to do is to replace the GPS antenna. If that does not fix it, try the CMM.

If this fails try putting the antenna almost on the top of the tower and measuring possible interference on 1.575 Ghz.

We think we figured out the problem with us losing satellites on our GPS, It looks like one of the public television stations changed one of there channels from 59 to 23. The Channel 23 is 524mhz, and talking with Verizon Wireless , the public station is putting out a spike off there exciter at 1.57ghz which is causing us to lose satellites, it was causing issues with them also, were working with them now. Thanks for your help guys.

Excellent. Glad you got it resolved.