CMM, multiple freqs, GPS

Hello folks!

I recently set up a CMM, 2 5200 BH20, 2 5250AP, 1 5700AP, and one 5700BH10 on the same tower. I seem to have everything working, but things get a little strange at night:latency, re-regs, etc. I have NOT installed the GPS synch. In your opinion is this very necessary? I am not looking forward to climbing a 100 ft tower to run more cables, but of course will if it is necessary.

Also, any tips for operating multiple freq gear on the same tower? I have at least 6 ft vertical seperation with all gear.


Yes you need to have the Sync cables installed for each device. Easier method is to use a CMMmicro. It passes the sync over the ethernet rather then having to run individual sync lines for each device.

It’s absolutely necessary. If you don’t have sync you will have to have at least 50 mhz separation between your AP/BH and you will cause interfirence to other canopy gear in your neighborhood.

Don’t worry about multiple frequencies, use them, with sync :slight_smile:


Well, today I went up to the tower and ran gps synch cables. I used bestronics cable, shielded. Made ends to spec. Used a 25ft lmr 400 with nmale connectors. I can’t get get any readings off the dang thing. keeps giving me a BAD POWER or some such thing. I tried different cables, recrimped the ends. nothing seems to working. This was a new CMM. This project is going south fast.

CMM Micro or CMM2?


Hello all.

So today I decided to replace the LMR cable, the pigtail from the GPS, and tested voltage and amps. Everything checked out. 5V through to the end of the cable (LMR) and .026A between to pigtail and the antenna cable.

My problems continue. This is what I usually see:

GPS Status
Pulse Status ERROR: No Sync!
Tracking Mode Acquiring SatellitesColdStart InsVisSat
GPS Time 12:40:43 GPS Date 01/01/2003
Satellites Tracked 0 Available Satellites 0

Height 0 meters Antenna Connection BAD - Over Current

Latitude N00 00.0000
Longitude E00 00.0000 Invalid Msg 5

Restart Count 0
GPS Receiver Information

Now, sometimes it says “BAD- undercurrent” as well and I get the error:
Bad GeomtryFastAcqPos FR2rawGPS DifferFix InsVisSat

I have replaced the synch cables, and have used different APs in slot one on the CMM and the synch cable to said AP in "master"

Sometimes satellites come up, but only for a few seconds. This is the second CMM2 to produce such results, so I am beginning to think I am doing something wrong. Do these antennas go bad? I am wondering if that is my next step.


**additional info **

SFTW P/N # 61-G10268A
MODEL # P283T12T11
HWDR P/N # 2

Yes the antennas can go bad. Take a known good GPS antenna and temporarily place it outside with a clear view of the sky and see how many sats you can track. I would say you have a bad cable, connector(s), and/or antenna if this is the second cmm with the same results.


Do you know where I can get just the antenna? Or perhaps a compatible one?

Just to clarify, this is the second (but separate) CMM that is producing the same results. My third tower is doing ok. I just thought it strange that right out of the box it would be bad.

Thanks for your replies!

undercurrent usually means that your cable is not ok.

right. but the cables have been checked, and rechecked. replaced the LMR, pigtail, and GPS synch at least three times each. Distance is under 50’ for all. I also measured and confirmed the expected voltage and amps.

Does anyone know where I can get a replacement antenna in the states?

Has no one had problems like this with the GPS?

YappaDappa try this.
1.unplug all radio power and sync cables from the CMM2
2. Connect GPS antenna
3. Connect an AP or BH master to port 1 power and sync
4. Power up the CMM2 and give it a few to aquire sats
5. Log into the radio in port 1 and look at gps page and for sync

if all is well you can now plug in all other radios.
The CMM2 must have a AP or BHmaster plugged into the master port or it will not pass sync to the other radios. Read section 19.5.4 on page 325 of the 7.3.6 system user guide. Hope this helps. If not I’m down in Ruidoso and can give you a hand. I have an extra antenna in stock if needed.

That’s very generous of you. Thanks for the tips. If you’re ever up North, give us a shout.

YappaDappa wrote:

Does anyone know where I can get a replacement antenna in the states?
Has no one had problems like this with the GPS?

I've never had problems with the antennas, but I had problems with the GPS boards. It's wise to have a spear part like this: ... m#prod3931

Replacement antenna: ... rodID=1576