Midland Radio SD125V3 Data Radio User Manual

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Topaz3, LLC. 10828 N.W. Airworld Dr. Kansas City, MO 64153 Tel: 816-891-6320 Fax: 816-891-8815August 2002UserGuideSD 125V3 DATA RADIO
SD 125V3Page -1-August 2002THEORY OF OPERATIONTHEORY OF OPERATIONThe SD 125V3 radio is comprised of two PCB's (an RF PCB and a digital PCB).These boards are connected with an 18 pin female and male connector. The digitalboard is interfaced with external data equipment through the 9 pin d-sub male connec-tor, which controls the radio and data receiving and sending. DIGITAL CIRCUITThe digital circuit is charged to be control for all of the signal path and set the frequen-cies to be set and selecting the desired channel.TX-Signal circuit The TX data signal comes from Pin 2 of Con 401, and goes through U404D. The TX-signal is amplified by U406C. The TX-signal is filtered by U405A & B which is a 4'thorder low pass filter, therefore, the filtered signal supply to the RF board for TX modu-lation.RX-Signal Circuit The RX- data signal comes from the RF board, which is connected with pin 10 of Con403. The RX-signal is switched by U404A and adjusted by RV403 and amplified byU407. The amplified signal goes to pin10 of Con 401.RSSI Detector From the RF board, the RSSI (Received Signal Strength Indicator ) signal comes toU403A & B through R461. The pulse is injected from pin 5 of U403B every 1 ms andC451 is discharged. After then, it begins to be charged by R464. Simultaneously,RSSI signal is input to pin 7 of U403A and those signals are compared. The comparedsignal is output from U403A. Pin 1 and the CPU detects the pulse width. The pulsewidth is varied by RSSI DC voltage. Therefore, the CPU determines the carrier detec-tion .EEPROM RX. TX channel and RSSI detection level as well as other data from the programmerare stored in the EEPROM. The data stored is retained without power supplied. Thisis a non-volatile memory . The EEPROM may have information re-programmed orerased. U402 is an EEPROM with 2048 capacity and data is written and read serially. Channel Selector One of 16 channels may be selected using the clip switch named SW401 . SW401encodes the channel number, selected into 4-bit binary code. The binary code plusone equals the channel number. The binary code is decoded by the CPU enabling theappropriate RX or TX frequency and associated data to be selected from theEEPROM. In the binary bit of SW401, the lower 2 bits are connected to Con402. Itcauses the low 4 channels to be selected from the external equipment's.DC to DC Converter The main DC power is injected to the DC to DC converter . The DC to DC converterregulates the various input power supply voltage and outputs a constant voltage of 7.5Volts. It is a source for all of the RF and digital circuits.The DC to DC converter is formed by U801, Q801, Q802, L801 and R804. U801 is aswitch mode DC to DC Converter IC. Input DC various appears as a voltage variousthrough R804. U801 detects the voltage and controls the switching pulse. As theswitching pulses, Q801and Q802 switches the input DC of various supply voltagesand generates the constant DC of supply voltage.
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Document ID278188
Application IDExlZXosaY4QPlq4nVi3wEw==
Document Descriptionusers manual
Short Term ConfidentialNo
Permanent ConfidentialNo
SupercedeNo
Document TypeUser Manual
Display FormatAdobe Acrobat PDF - pdf
Filesize42.79kB (534897 bits)
Date Submitted2002-10-21 00:00:00
Date Available2002-10-10 00:00:00
Creation Date2002-08-28 15:56:00
Producing SoftwareAcrobat Distiller 4.05 for Windows
Document Lastmod2002-08-28 15:58:26
Document TitleDesign Docs.book
Document CreatorFrameMaker 6.0
Document Author: dcline
FCC ID Filing: F3JSD125V3

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