ProMark 120, 220 (legacy ProMark 100, 200)
MobileMapper 120 (legacy MobileMapper 100)
can all benefit by connecting to an external source of corrections. Each of these devices have an internal GSM modem, which can be activated by installing a GSM Sim card. An alternative method is to make a Bluetooth connection to a cell phone, however this is extremely difficult.
In the United States, Mexico and Canada many areas are better served by CDMA cellular service (Verizon in the USA.) These devices do not have a CDMA modem. So generally they connect to the internet by WiFi.
But the devices do not have built in WiFi so a SDIO card is used. And the card sticks out the side of the receiver:
You can easily remove the flap:
But this is not weatherproof.
Generally we make it weatherproof with electrical tape:
If you live and work in an area with EXCELLENT GSM coverage, then you probably don’t care about any of this because you can use the internal GSM radio. However if you plan on using a MiFi (wireless hotspot) which [ I think is the way to go ] then you need to consider this as you think about purchasing a ProMark 220.
In spite of the stupid tape solution, which definitively sucks, the ProMark 220 is still an excellent network rover. It’s performance is nearly equal to the ProMark 800, at a fraction of the price.