Tag Archives: PM120

MiFi vs. Sim Card

Last October I buried comments about MiFi vs. Sim Cards in a post about Using a Z-Max receiver with a network connection.

Well, a week ago I purchased a used ATT MiFi device on eBay (AT&T Sierra Wireless Aircard 754S Elevate 4G LTE Mobile Hotspot Modem Router) and had a (wait for this) FANTASTIC experience.

I bought a used MiFi device because I did not want to encumber my #1 sim card (I have two) with a contract. The device was shipped within an hour and it worked perfectly when I received it. But it would not log onto the local ATT network.

So I called ATT described what I wanted to do and was immediately escalated up a level to an amazing support guy. He made the back-end changes to the card’s registration and the MiFi worked (they just added LTE in Salt Lake so the speed at my house hovers around 20 Meg download which is 10 times faster than the DSL. The card is good for 5 GB of download, you probably only need 200 Meg if you are only going to survey.

When I made the change, I was positive that the card would no longer work in the SP/Ashtech devices. However everything I have tried so far (PM100, PM120, PM220, PM500, PM700, PM800, LT30, MM10) has worked just like before.

[I want to reiterate that the ATT Tech Support guy (who I probably should not name, but will) Aarron Lequia was simply-absolutely-amazing. He made the changes and then patiently waited for me to try the card in a 1/2 dozen devices, just in case I wanted to revert back to the old configuration. The customer support at ATT could not have been any better.]

Now, back on topic:

Advantages of Using Mi-Fi to Data Collector Method

  1. You can see the status of your internet connection on the Mi-Fi screen:
    With a glance, you know your MiFi device is online.
  2. The Wi-Fi connection from a Surveyor+ to the MiFi is bullet-proof. It just happens and works every time.
  3. You can get a Mi-Fi device from Verizon for use where ATT and TMobile have no service!
  4. Typically the price for a Mi-Fi subscription is lower than a sim card. And because no phone service is associated with the Mi-Fi, there is no tax on the service.
  5. You can use the Mi-Fi with other devices (tablet, laptop, multiple rovers), leveraging the internet service investment.
  6. The data rate connection is way faster with the MiFi. In the case of a PM220, it appears to be 100 times faster. If you are using Dropbox to move DXF files, this could be a big deal.
  7. My cell phone does ‘data roaming’ in South West Wyoming. But my MiFi does not (I do not understand why.) So my MiFi gets unlimited roaming data but my phone does not. By connecting my phone to the MiFi I can minimize my roaming data.
  8. There does not appear to be any tax appended to the MiFi bill. (But holy cow, there are plenty of taxes added to my cell phone bill.)
  9. We install a small tool that allows us to remotely control the screen and keyboard on your data collector. If your phone does not support  simultaneous voice and hotspot, then we can’t talk to you while we fix your receiver.

Disadvantages of Using a MiFi

  1. Plan costs a bit more per month.
  2. On the PM120,220,100,200 and MM120,100 you have to have a WiFi card in the side of the unit.

Disadvantages of Using a SIM Card in a Rover’s Internal Modem

  1. Once you make a connection, you can’t read the signal strength on any of the devices I sell. The signal strength from before the data connection is shown, not the current signal strength.
  2. Entering all the passwords, user names, server names is a pain in the butt. (This is now mitigated as I just leave everything blank and it works the first time.)
  3. The data collector and GPS internal modems do not support 3G and 4G connections.
  4. The card can only be used with one device, unless you remove it which is difficult.

Interesting Complaint with MiFi

One note on MiFi. I have heard complaints from others that their data collectors will disconnect WiFi from their MiFi while they walk or drive around a neighborhood.

The problem is: they have to ‘reconnect’ to the network when their data collector moves between networks.

I have never personally seen this and I believe it to be a bad configuration in the data collector. The setting is “Automatically Connect to Open Networks”. Obviously it should be ‘unchecked.’


So, if you’re thinking about provisioning data service to get network corrections, I still recommend a MiFi device.

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Repairs on Legacy Equipment

We can now offer repairs on legacy Ashtech equipment:

  • MM6, MMCE, MMCX, PM3, PM100, PM200, PM220 screens and touch-screens
  • ZMax Battery Re-Cells

Prices are reasonable and we are including FedEx 2-day return shipping. You can see a list of the repairs and prices [ here ].

For many repairs, the factory is a great option. But for some items like PM3 screen replacement our price is $1,100 less!

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