Related Manuals for Cobra MRF55
Summary of Contents for Cobra MRF55
- Page 1 Theory of Operation Marine Radio MR F55 & MR F75 Total pages: 4...
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Page 2: Functional Description
156.025MHz to 163.275MHz with WX and DSC. Functional as follows: 1. MRF55: Channel Up / Down, Emergency channel key CH16/9, WX/UIC key, Channel Scan key, TX power HI/Low key, Dual watch channel key, Call/set key, Distress key, Squelch control volume, DC power ON/Off and Audio Volume control, External Speaker Jack and GPS Jack, PTT key. - Page 3 The unit DC power supplies is 13.8V and path as follows: MRF55: T102 – L124 – SW100 (Rotary switch) – IC111 (LM7805) – VCC+5V output. MRF75: T102 – L124 –-- R125 – IC108 (LM7805) -- +5V output to MCU (CPU-DC).
- Page 4 • High – low TX power control circuit The IC112 LM358M, transistor Q108 and Q109, diode D102 and external resistors and capacitors buildup the Automatic Power Controller. TX High power output 25 watts @ 50Ω loading: High power mode the CPU pin25 output is low, the transistor Q105 is rest. Then adjust the VR101 to change IC112 pin3’s voltage and the Q116 collect output can automatically to control the RF power module pin2’s Gate voltage to control the power gain output.