FlexRadio Systems FLEX-1500 Manuale utente

Revision 1.0

FlexRadio Systems

FLEX-1500

Software Defined Radio

Service Manual

Author: raham Haddock, KE9H

Revision 1.0

Contents

Introduction ..... 3

Theory of Operation .. 4

Alignment, Test and alibration.... 11

Troubleshooting and Diagnostics ....... 14

Assembly and Disassembly....... 15

Fuse Replacement... 16

Appendix “A” Schematic, PTRX (Transceiver) Board

Appendix “B” Schematic, PPA05 (RFPA) Board

Appendix “ ” Boards, Top View.

Appendix “D” Test Points and Bus Access.

Appendix “E” Test Fixtures.

Appendix “F” Parts List.

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Introduction

The FLEX-1500™ QRP Software Defined Radio is an entry eve QRP radio and is a so

suited to be the idea IF deck for VHF-Microwave operation. It provides a of the

advantages of a software defined radio, inc uding the sophisticated high performance

fi ters, panoramic spectrum disp ays and computer based graphic interface characteristic

of a software defined radio.

This service manua assumes that the reader / service technician is fami iar with the

operation of the radio and PowerSDR contro software. If additiona information is

required on those topics, p ease refer to the Product Manua and Quick Start Guide.

Front View - FLEX-1500

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Theory of Operation

Refer to the B ock Diagrams on the two fo owing pages.

The detai ed schematic are inc uded in Appendix “A” and Appendix “B”.

The unit is powered by +13.8 Vo ts DC, supp ied via the 2.5 mm x 5.5 mm coaxia power

connector on the rear of the unit. The unit has an interna 3.0 Ampere fuse that wi b ow

if the unit draws excessive current or if the po arity of the power connected to the unit is

reversed.

The FLEX-1500 CPU (TAS1020B Streaming USB Contro er) wi communicate via

USB for both contro and streaming baseband data with the host CPU running the

PowerSDR software. The CPU in the FLEX-1500 has contro of a switching, signa

routing, frequency generation via the DDS, F exWire port, audio amp ifier, as we as

audio and baseband routing, CODEC c ock generation, data conversion, gain and eve

contro s for the radio.

Communication between the F ex-1500 radio and the host computer is via a USB

connection capab e of USB 1.1 or higher eve USB operation. The protoco is USB

“Fu Speed” or 12 Megabits per second data transfer rate.

Power Systems and Distribution

The transceiver board requires a source of regu ated +5 Vo ts at approximate y 400 mA

to function. +3.3 Vo ts is supp ied to the board in genera by a inear +3.3Vo t regu ator

derived from the +5 Vo t ine. Additiona +3.3 Vo t and +1.8 Vo ts required to operate

some of the integrated circuits is provided by point-of- oad regu ators in the vicinity of

the IC.

Overa power for the unit is derived from the +13.8 Vo t input on the RFPA board.

This 13.8 Vo ts direct y supp ies the re ays and power amp ifier transistors. It is a so

feeds two regu ators. A 6 Vo t regu ator is switched on when transmitting, and off when

receiving. This switched +6 Vo t output is used to bias the RF power transistors. A

separate +5 Vo t regu ator supp ies power for the SPI decoder and re ay driver IC on the

RFPA board, as we as supp ies a +5 Vo t power to the transceiver board (PTRX) via

the board to board interconnect system.

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ontrol Busses

There are severa contro busses that interconnect the radio. A USB “Fu Speed” bus

interconnects the host computer running PowerSDR with the on-board CPU, the

TAS1020B. Contro from the TAS1020B CPU to the rest of the radio and externa

contro is via an I2C bus system, and two SPI busses.

Firmware for the CPU is resident in a oca (I2C) EEPROM on the transceiver board.

Upon power up, the CPU wi ook for the presence of a proper y programmed EEPROM,

oad this code, begin execution, and register with the host computer as a FLEX-1500

device. In the absence of the EEPROM, or ack of correct y identified firmware, the CPU

wi execute from interna ROM, and identify itse f to the host computer as a “TI DFU

device.”

The FLEX-1500 CPU wi communicate via USB for both contro and streaming

baseband data with the host CPU running the PowerSDR software. The CPU in the

FLEX-1500 has contro of a switching, signa routing, frequency generation via the

DDS, F exWire port, audio amp ifier, as we as audio and baseband routing, CODEC

c ock generation, data conversion, gain and eve contro s for the radio. A of the above

must be trans ated from oca hardware and register contro s to the Command and Data

structures chosen for USB transport and interface in the host to the PowerSDR software.

I2C Bus

The I2C bus exists as three instances.

(1.) The computer bus (I2C-C), which contains the (master) CPU, the EEPROM

containing program memory and ca ibration parameters, and the Bus Mux.

(2.) The Interna I2C bus, (I2C-I) containing the two bus expanders and the

CODEC chip.

(3.) The Externa I2C bus (I2C-E) which is routed to the F exWire DB-9

connector, and is on y used in conjunction with an externa F exWire device.

The I2C Bus Mux se ects whether the Computer I2C bus wi be connected to the Interna

or Externa I2C bus extension at any given time, as we as passing any interrupt requests

upwards to the CPU. Since the EEPROM and the Bus Mux are on the computer bus, their

addresses wi appear in a I2C bus spaces.

I2C Bus Structure

The I2C bus address va ues are provided according to the TI convention, where the

address is an eight bit word, expressed as two hexadecima characters. The east

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significant bit is actua y the ~read/write bit, but is a ways presented as a “0” when the

address is expressed. The TAS1020B is the I2C Bus Master and is a ways connected to

the I2C Mu tip ex Chip and the EEPROM.

When the Bus Mux is set to “Outside,” the I2C bus is routed to the appropriate pins on

the F exWire connector. When set to “Inside” the I2C bus is routed to the CODEC, and

the two Bus Expanders, which convert I2C commands to many high/ ow outputs used to

contro the individua switches that contro signa routing in the radio.

The Audio Amp ifier is contro ed by genera purpose outputs from the CODEC.

SPI Bus

There is a so a SPI bus, used to contro the DDS and the RFPA. It appears as two

physica instances, a 3.3V version and a 5V version. The SPI is outbound contro on y,

for both the AD9951 DDS and RF PA board.

The AD9951 DDS is contro ed via the 3.3 Vo t SPI bus, direct y from the CPU.

The DDS can be programmed to operate with either a 20 MHz or 38.4 MHz reference

input. The 20 MHz signa comes from doub ing the externa 10 MHz input, and the 38.4

MHz is generated by an onboard temperature compensated crysta osci ator.

The TPIC6B595 Re ay Driver is contro ed by the 5 Vo t SPI bus, and contro s the

fo owing re ays according to the band of operation or transmit/receive status.

A “High” SPI contro bit is the active state, which provides a LOW output from the re ay

driver to turn the re ays ON.

I.C. Name

Bit

Name

Function

Initial

Drain0 0 4 15M Active = 17 or 15 Meter Band 0 = Inactive

Drain1 1 5 160M Active = 160 Meter Band 0 = Inactive

Drain2 2 6 20M Active = 30 or 20 Meter Band 0 = Inactive

Drain3 3 7 6M Active = 6 Meter Band 0 = Inactive

Drain4 4 14 80M Active = 80 Meter Band 0 = Inactive

Drain5 5 15 10M Active = 12 or 10 Meter Band 0 = Inactive

Drain6 6 16 XMIT HIGH = Trans it ode, LOW = Receive ode 0 = Receive

Drain7 7 17 40M Active = 60 or 40 Meter Band 0 = Inactive

RF Signal Processing

The incoming RF signa s may be received via the antenna connector on the RFPA board,

the transverter receive connector, or the transverter common connector. These signa s are

routed via the appropriate bandpass fi ter, then either direct y to the preamp, or through a

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20 dB pad to offset the gain of the preamp. The output of the preamp is fed to the QSD

down-mixer, with an output of I and Q baseband signa s in the range of 0 to 24 kHz.

The QSD down-mixer is a so supp ied with a quadrature oca osci ator signa which is

derived from the DDS. The DDS operates at twice the desired oca osci ator signa ,

passes though a 120 MHz ow pass fi ter, into a Johnson Counter that both divides the

DDS frequency by two, as we as generates the two quadrature oca osci ator signa s.

In transmit, in a reverse manner, I-Q baseband signa s from the CODEC in the baseband

range of 0 to 24 kHz are supp ied to the QSE, a ong with the quadrature oca osci ator

signa s at the operating frequency, resu ting in a direct QSE output on the fina transmit

frequency, which is routed via the bandpass fi ters to either the transverter output

connector, or the input to the RFPA.

Baseband Processing

In the receive direction, output I and Q signa s from the QSD are passed through a set of

OpAmps that have 18 dB of signa gain and 28 kHz ow pass fi ters, then sent to the

CODEC for digitization and transmission to the host computer.

In transmit, ana og I and Q signa s output from the CODEC are fi tered in a 26 kHz ow

pass fi ter to remove wideband digita noise, then sent to the QSE for up-mixing.

ommunications

In the receive configuration, digitized I and Q signa s from the CODEC, representing the

received pass band, are transferred using the I2S protoco to the Streaming USB

contro er. This contro er then transfers this information via the USB protoco to the

host computer. Processed and demodu ated audio is returned via the USB protoco to the

contro er, then transferred to the CODEC via I2S protoco for conversion into ana og

audio signa s.

In transmit configuration, digitized microphone audio signa s from the CODEC are

transferred using the I2S protoco to the Streaming USB contro er. This contro er then

transfers this information via the USB protoco to the host computer. Processed transmit

audio in a digita I and Q format is returned via the USB protoco to the contro er, then

transferred to the CODEC via I2S protoco for conversion into ana og baseband signa s to

drive the QSE up-mixer.

In the BITE (Bui t In Test Equipment) configuration, digitized I and Q signa s from the

CODEC, representing the received pass band, are transferred using the I2S protoco to

the Streaming USB contro er. This contro er then transfers this information via the

USB protoco to the host computer. Transmit test signa s in a digita I and Q format are

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sent via the USB protoco to the contro er, then transferred to the CODEC via I2S

protoco for conversion into ana og baseband signa s to drive the QSE up-mixer.

Audio Amplifier

An audio amp ifier is present, capab e of driving stereo headphones, or stereo powered

speakers, in the Stereo configuration, or a monophonic speaker direct y, in the Mono

configuration. In stereo, each of the two amp ifiers are carrying the appropriate eft or

right channe information, and driving a ow power amp ifier suitab e for headphones or

high impedance oads. In the Mono configuration, the two incoming stereo signa s are

mixed together to form a sing e mono signa . This is fed to one amp ifier direct y and

inverted and fed to the other amp ifier to form an “H-Bridge” speaker amp ifier. In this

mode the speaker must be wired to bridge the amp ifier output (connect to tip and ring on

stereo speaker p ug) with no connection to ground.

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