Radio Interface Module - RB-RIM-Lite

1. Repeater Builder's RB-RIM-Lite
2. RB-RIM-Lite Schematic
3. Interface DB9 Connector
4. CMedia CM119 USB Audio Controller
5. Layout
6. RB_RIM LEDS
7. The C-media CM119 Chipset

Repeater Builder's RB-RIM-Lite

• Instead of two channels of low-pass filtering, the RIM lite only has one.
  Typically only one channel of filtering is needed since there is only ONE modulator
  in a given radio. This filter remains 5 pole with a "knee" of approximately 10kHz.
• The charge pump and additional amplification stages have been removed to reduce cost.
  This module still makes over 1Vp-p of audio which is adequate for driving most modulator
  circuitry directly.
• The buffering of the COS and CTCSS inputs has been reduced to a simple diode.
  Again reducing circuitry that is not often used.
• The discriminator audio input attenuator is now a potentiometer. No more external voltage
  dividers necessary to knock the radio's audio down to the CM119's input level!!
• The DB-25 connector has been replaced with a DE-9. This simplifies connectons and reduces
  product size. This means that the additional I/O pins are not brought to the outside world.

RB-RIM-Lite Schematic

Interface DB9 Connector

• 1 - Encode sub-audible tone to TX (See Note A)
• 2 - Audio to TX
• 3 - COS logic from RX (See Note B)
• 4 - CTCSS logic from decoder (See Note B)
• 5 - PTT to TX
• 6 - Discriminator audio from RX
• 7 - Spare (could use to remote HeartBeat (HB) LED
• 8 - Ground
• 9 - Ground

CMedia CM119 USB Audio Controller

Layout

RB_RIM LEDS

1. Green PC_OK - Pin 7 goes Low when the PC and Interface are communicating successfully.
2. Yellow HB - HeartBeat
3. Red PPT - On when PTT is active

The C-media CM119 Chipset