[Motorola] Sinclair Radio Laboratories Filter Duplexer M150-3B

[Geoff Fors]

I do believe those are duplexers added to MTS and RCC mobile telephones in 
the years before IMTS came into service.  They do not have to be very big as 
the frequency separation is about 6 MHz and the increased loss of a small 
package was tolerable in the system.  Later mobiles had the duplexer 
built-in, either as Motorola's combination receiver front end and duplexer 
(Trisolector) or as a separate unit occupying a portion of the chassis.

Geoff
WB6NVH