CMM Micro not finding Satellites

I’ve gone through 2 CMM Micros now and both of them can’t find any Satellites. We’ve tried different GPS cables and antennas to no luck.

I’m wondering if there is a weird setup issue we need to do with the CMM Micro. It just seems weird that I would get 2 bad CMM Micros.

Any help would be greatly appreciated.

Make sure the antenna can see the southern sky.

It can take 10 minutes to acquire satellites and get a lock the first time out of the box.

Thanks Jerry but the Antenna is mounting on a pole probably a few feet above the top of the building facing south. The first CMM was hooked up and running for a few weeks and nothing.

Now the new one and still nothing and its been 24+ hours.

Here are some screenshots from my cmm micro.





Are you near a Military base?

No, a lot of other towers though, probably 15-20 in a 3 mile radius.

But just down the hill about 200 feet away, there is another Canopy system with a CMM Micro and its GPS and I assume it works for them.

Take a look at the spectrum at around 1500MHz (GPS signal). I’m guessting interference is blocking the GPS signal.

What cable are you using between the CMM and the GPS antenna? And how long is it?

Jerry Richardson wrote:
Take a look at the spectrum at around 1500MHz (GPS signal). I'm guessting interference is blocking the GPS signal.


What kind of devices (military or otherwise) would operate at this frequency? I have a site I have never been able to get to sync properly due to some sort of interference so it would be nice to know what I should look for.

The military purposely causes interference when they want to dumb down the GPS capabilities in a certain region.

A very high power 750MHz signal that is over driving an amp and/or has bad filters will pump noise at 1500MHz.

Jerry Richardson wrote:
The military purposely causes interference when they want to dumb down the GPS capabilities in a certain region.

A very high power 750MHz signal that is over driving an amp and/or has bad filters will pump noise at 1500MHz.



ive seen it first hand. was camping in the state park very near to camp david (at night we could see the spotlights in the woods) and nobodys cell phones or GPS would work.
Frothingdog.ca wrote:
What cable are you using between the CMM and the GPS antenna? And how long is it?


RG58 i think is whats written on my invoice. I'll be able to double check on the cable tonights. Its 25' in length.


Jerry Richardson wrote:

The military purposely causes interference when they want to dumb down the GPS capabilities in a certain region.

A very high power 750MHz signal that is over driving an amp and/or has bad filters will pump noise at 1500MHz.


If am I getting interference wouldn't the nearby Canopy system's GPS fail too? I'll have to give them a call see if they are having any problems.

I bet the RG58 is what’s doing it. You need to use a 50Ohm cable. Try LMR240. I bet that’ll fix it.

And yes…if it was interference then the Canopy GPS shouldn’t be working either, that’s why I think it’s just the cable.

I’m with Frothing - likely the cable. RG58 is 50 ohm, but lossy. As suggested LMR240 or LMR400 is a better choice.

However, if you have continued problems, I would not rule out interference. The nearby operators may also be experiencing issues so it might be worth a call.

the best is try with a small cable and a different area to see if CMM / GPS antenna are fine.

We had a similar problem with a working CMM micro, the engineer just opened the box and was trying to work on AP when we lost sync, and no satellite could be seen. After closing the cmm box all was well.

We use LMG’s CTM units for GPS timing at our larger tower sites - I’m assuming the answer to my question is no, but is it normal behavior for these units to lose GPS every now and again?

Over the course of the last 5-6 months, I’ve lost GPS signal 3 times. The first two times it locked on sats again within about 15 minutes. Today it has done it again and has been down for about a half hour.

It’s usually tracking about 7 satellites, so I find it hard to believe it would be cable/antenna related. Suppose it’s interference?

Frothingdog.ca wrote:
I bet the RG58 is what's doing it. You need to use a 50Ohm cable. Try LMR240. I bet that'll fix it.

And yes..if it was interference then the Canopy GPS shouldn't be working either, that's why I think it's just the cable.


RG58 is 50 ohm (as already stated). We use RG58 in lengths from 10-25' for our GPS at all of our sites without a problem. I'd recommend the OP check the termination points and/or move the GPS to see if anything could be obstructing/interfering with the signal.

* Jerry beat me to the punch.....

We have a CTM that has not lost GPS in the 8 months since it was installed.

I have a CMMmicro that was periodically losing sync. I move the antenna and it’s been solid since.

Jerry Richardson wrote:
We have a CTM that has not lost GPS in the 8 months since it was installed.

I have a CMMmicro that was periodically losing sync. I move the antenna and it's been solid since.


How far did you have to move the antenna? Right now I've got it installed near the external enclosure on a platform that extends out to the east of the grain leg. It has a clear view of the southern sky from this point.

Other than shifting it a few feet either direction, the only option I would have is moving it about 40-50 feet away from the enclosure which would not be ideal (long cable run).

Moved it 4 feet around the tower. It was on the SW side, so I moved it to the SE side.

Thanks.