Here is one of the mistakes I would most like to save the customer from: do not buy a Garmin radar and subsequently discover that your plotter cannot display it.
ECHOMAP and STRIKER
Garmin's current support information states directly that ECHOMAP and STRIKER models are not compatible with Garmin radar. ECHOMAP can still be a strong solution for charts, sonar, and fishing, but radar is not a feature you can simply add later.
GPSMAP
Garmin's GPSMAP family includes models with Garmin Marine Network that can work with compatible Garmin radars. The precise compatibility depends on the GPSMAP model, network ports, and radar.
What should you send to me?
Send the model number of your current plotter – e.g., GPSMAP 922xs or ECHOMAP UHD2 72sv – and preferably a photo of the back/connections. Then I can check whether radar can be integrated and which cables/network parts are missing.
Radar requires more than just the radome
Placement, power, network, and potential heading information are important. For radar overlay, precise heading data from a compatible sensor/autopilot is better suited than just GPS movement direction, especially when the boat is drifting sideways or backwards.
See Garmin radar · See Garmin chartplotters