Probably one of the least used items I've ever come across. I think the major problem for this is that due to it having the option of a backpack slot people pick them up one time and either drop the item instantly or lug it back to their base and keep it there.
There is next to zero incentive to have a group mate carry this item on them as you move around the map due to its base weight PLUS the additional 10Kg from the Car Battery that is needed in order to use the item. That totals out to "About 25Kg" in-game. That is more than the weight of 2 plate carriers combined.
Overall the Field Transceiver's weight needs to be heavily reduced and/or the Car Battery's weight needs adjusting.