Electronic – Identify 4 pin Connector

Assuming the ruler is showing millimeters, I'd say that the connector is of JST-XH-2.5 mm type with two pins. Sometimes, these connectors are sold and marked with 2.54 mm in their name, since that is a common spacing for inch-based measurements. Such connectors are commonly used for battery packs, so you might be able to find one, or a cable with one attached, in stores that sell equipment for radio-controlled planes/cars/boats etc.

My guess is that the radio was intended for use with a small loop antenna, such as one depicted in this photo from Wikipedia:

Most likely, two ends of such antenna would be connected to the appropriate female connector and then plugged into the radio.

Looks like TE connectivity "AMP Power Series" connectors. There are several versions (15/30/45/50/75/120/whatever). Here is the datasheet. Look starting from page 141, take a caliper, and check which one is yours.

Edit: I'm pretty sure it is actually the AMP Power Series 15/30/45. The housing is the same for these three versions, the difference being the contact and its current carrying capability. It may be more difficult to guess which one of these variants it is. Maybe you can just try the one that has the highest capability, and check that it mates appropriately.