This appears to be an early Blue Force Tracking (Wiki: BFT) beacon transmitter designed to be mounted on a vehicle or carried by a soldier. BFT was motivated by a desire to minimize Friendly Fire (Wiki).
Force XXI Battle Command Brigade and Below (Wiki) started testing in 1995 and was fielded in Operation Desert Storm/Shield (Wiki). Blue Force Tracking got started in 2008 (Ref 1), and BFT-2 started in 2012 (Ref 2).
This is closely related to Situational Awareness (Wiki: SA). In a military context this typically has to do with knowing where you are and knowing where friendly and enemy forces are. The DAGR GPS receiver has two mapping modes. In one mode you can load a rasterized image, like from an aerial photo and in the other you load a map as a vector file. The vector file looks like a topo map and a small file can cover a large physical space and so is typically used for SA.
Modern radios have a provision for either an add-on GPS or a built-in GPS to provide the user with SA. This works both ways. That's to say the radio operator sends his/her location with each transmission sent. Also with each signal received the other operator's position is captured. It can be displayed as alphanumeric on the radio, but for a map some radios require an external device. See: Harris RF-5800V-HH.
Another aspect of this is that an enemy should not be able to use the position signal in any way. They should not be able to see the data and they should not be able to use Direction Finding techniques to locate the source of the signal. Ideally they should not be able to hear the signal at all. This latter requirement might be met using direct sequence spread spectrum (Wiki) modulation. This is different than frequency hopping (Wiki), like is used in the SINCGARS radios (SINCGARS, RT-1439, RT-1523).
Ref 1. DEfense-Aerospace: General Dynamics Awarded $34 Million for M1A1 Abrams Tank Upgrades, September 5, 2008 - "M1A1s are configured with armor upgrades and additional mission-critical technologies to bolster crew situational awareness (SA). The SA package include second-generation Forward-Looking Infrared, Far Target Locate, Blue Force Tracking (BFT)/Force Battle Command Brigade and Below (FBCB2), a tank-infantry phone, a .50 caliber thermal sight, a power distribution box, a rear slave receptacle, an eye-safe laser rangefinder, and driver's vision enhancement."
Ref 2. Defense Systems: Next-gen Blue Force Tracking system gets major boost, Mar 2, 2011 - "A next-generation situational awareness system will start fielding in fiscal 2012..."
Ref 3. Force XXI Battle Command Brigade-and-Below (FBCB2) AN/GYK-55 (NSN: 7010-01-500-2271), 1 Aug 2008, 374 pages.
What appears to be a Toughbook (CF-28, CF-30) laptop computer runs software that works with the AN/GYK-128 and CA-131/P Mission Data Loader (MDL), AN/GYK-55 Create Device Digital Computer (terrestrial based only) either with built-in GPS or an external PLGR or DAGR GPS. EPLRS can also be on the tactical LAN.
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