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SBHT - VHF DIGITAL RADIO

SBHT is a data/digital voice radio capable of greater than 4 watts of power initially on the VHF Ham bands.

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STM32F4 based VHF Data Radio. Capable of transmitting at > 4 watts with support for modulation schemes used in DSTAR, Nexedge, DMR (GMSK,C4FM). Also new development of new protocols with support for TDMA. A design small enough to carry in your hand and powered by battery.

Planned uses for this design:
HT/Mobile VHF Digital Audio Radio (DSTAR,DMR, Something New) (DMR Requires external AMBE Codec)
Data Modem for Telemetry
TDMA based Repeater (No duplexer and same frequency repeating)
Experiment board for GMSK/C4FM

SBHT is based on the Analog Devices ADF7021-N Transciever and controlled by a STM32F4. Speaker and MIC circuits are on board to allow this data modem to also digitally transmit audio with various codecs either placed on the STM32F4 or off board AMBE codec DSP board. This was initially built and tested as modules (PA, SWITCH, LNA, FILTERS, TXRX, MCU, POWER, etc).

The current filter configuration is designed to work well in the 144Mhz - 148Mhz Amateur Radio Band. With filter modifications the design will work in other bands.

The PA module output is controlled by the STM32F4.

This design is an attempt to compromise size / performance. It is small and battery powered. The ADF7021-N is designed for low power operation but we'll see how well optimized the output can be and the PA is adjustable.

NOTE: The ADF7021-N is designed as a low power device. It not really well suited for high power amplification. If you build one of these be sure to check the output for spurs.

  • 1 × STM32F405VG Microprocessors, Microcontrollers, DSPs / ARM, RISC-Based Microcontroller
  • 1 × ADF7021-N RF, IF, RFID, ZigBee Semiconductors and ICs / Transmitters, Receivers and Transceivers
  • 1 × ra07m1317m PA VHF. Battery Powered / Low Voltage . 10W PA

  • RX/TX

    Shane Burrell05/28/2015 at 11:48 0 comments

    I've been doing some testing receiving and transmitting 4FSK packets. Phase noise limits output to about 3 watts. This could be reduced by using an external VCO design and different ADF IC.

  • Firmware Load

    Shane Burrell04/16/2015 at 03:02 0 comments

    Slow steady progress on board turn up and assembly. All three power rails are up. STM programmed and talking to the transceiver.

  • Reflow of first Board.

    Shane Burrell04/10/2015 at 00:12 0 comments

    Reflowed rev of the complete compact design. Went well other than skewing the USB connector.

  • Board Arrival and Prep.

    Shane Burrell04/09/2015 at 00:05 0 comments

    Boards arrived.

    OSC1 traces were cut and prepped for connection to OSC2 after reflow. Had to add the holes for Tag Connect. Kicad option was turned off for non plated holes so drill hits weren't made.

    Setup stencil and last few checks of reflow oven profile.

  • OLED Driver Progress, STM32 I2C woes.

    Shane Burrell04/04/2015 at 01:37 3 comments

    I've spent several hours the last few nights trying to figure out why output wasn't working. First I assumed it was an upgrade to Cube 1.5 which is a fairly safe bet, as the HAL drivers are a buggy abstraction layer as to what is actually going on. Then it finally came to me that the proto board had pullups and the Discovery board did not. I enabled the internal pullups and bingo it was working as it should. OLED driver for the SSD1306 is now working along with fonts and mono bitmaps. I've also improved my ADF init strategy which should now support fine cal mode. Hopefully new proto boards will be in late next week. More good news the VHF PA footprint/package can be had in a UHF version which I've ordered samples. Other than a few passives and finding a replacement Tx/Rx switch it should be trivial to have a vhf version and uhf version.

  • Simulation, Testing, Firmware.

    Shane Burrell04/02/2015 at 00:50 0 comments

    Big strides tonight getting all (including rarely used) sections of the ADF driver working all in a nice format and verified with test board / peek at logic . Phase noise from the datasheet was a concern however simulation and testing so far it doesn't seem to be with external PA and ramp requirements. I don't plan to drive up the full PA level and everything looks good for up to 4 watts output. Made minor change to gerbers for next board spin. Swapped OSC1 and OSC2. OSC2 will do CMOS level tcxo. OSC1 will not requires .8v peak to peak. CMOS parts are easier to come by. Verified with ADF module switching between GMSK and 4FSK. Refactored ADF driver to later support UHF band optionally.

  • Stencil Arrival. More work on firmware.

    Shane Burrell04/01/2015 at 00:02 0 comments

    Stencils arrived today. Waiting on boards. More work on the firmware. Upgraded STM HAL to new version 1.5 and backported my changed to the HAL. These abstraction layers never work exactly the way you need them to so modifications are usually necessary. Should be ready to place and reflow when boards arrive.

  • More ADF-7021-N Driver work.

    Shane Burrell03/29/2015 at 23:21 1 comment

    A bit more work adding cal to driver.

  • More Firmware work. GPS/OLED mockup.

    Shane Burrell03/28/2015 at 23:13 0 comments

    Added support for spi flash . Bit more mockup on oled display and gps.

  • Firmware Progress...

    Shane Burrell03/28/2015 at 01:09 0 comments

    The first build of firmware is done and only minor tweeks should be needed. Tested with a STM32F4Discovery board. The driver for the ADF7021-N should be complete and verification via logic analyzer indicates it should bring up the transceiver and go into RX mode. I've added a PTT input definition to one of the many extra pins. Pressing the PTT will transmitted "Hello World" in the first frame and a AMBE audio snippet afterwards saying "Hello World". The OLED display works great even for its very small size. Bright and easy to read low power budget. The Neo GPS module I've used before and I have embedded its output in the last data frame thats sent. Made some small modifications to the new STM CUBE library as it never quite works the way you want it to.

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  • 1
    Step 1

    Currently during revision 0 a few brave souls are assembling boards. If you really want one let me know but there will be little to no support during the revision 0 build. Rev 0 Gerbers are available on GITHUB. https://github.com/shaneburrell/SBHT

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Themis wrote 11/29/2015 at 21:27 point

Very intresting project , how working as dmr repeater? i see only one adf? maybe im wrong. Thanks SV4QXF

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