Radio, yes AM-SW-FM radio by DSP radio chip

Just a decade ago, shortwave radio should be made of bunch of coil and resonators. Nowadays, nothing needed!

Similar projects worth following
It is not up-to-date topic but several one-chip DSP radio is available on market. These chips realises very wide band receiver (generally AM-SW-FM) without any conventional inductor and resonator but single chip controlled by I2C. Indeed I made several one before I joined and this time I made "summary" of it. It consists of KT0915 (DSP radio chip), ATmega328 (controller) and LiPo charging circuit.

A few years ago, I made several DSP radio consisting of wrapping wires and universal circuit board as shown in the left side of the picture. In those days I did not use Eagle or some cad soft, just I made I want.

It is still surely working but I did not make notes of schematic (indeed it has gravity sensor, RTC and DSP radio) and I myself don't remember the details and this time I make it a bit smarter form.

This is the whole schematic. In the schematic I should point out "AT42QT...." in right-down part is just put to use SOT23-6 form factor and real parts number is TP4057, LiPo charging controller. JP2 is antenna terminal and even 21st century, yes we need analogue part, ANTENNA! between 5-4 of JP2 should be connected to ferrite-bar antenna (or relevant) and 2-3 pins are "antenna terminal" for shortwave and FM radio.

It consists of KT0915 and ATmega328. KT0915 is a I2C controlled DSP radio chip and Mega328 controls whole system including OLED display. On OLED display, frequency information and stereo/non-stereo RSSI for FM reception is indicated. This is not character OLED and more attractive user-interface will be possible (I did not yet) .

Receiving band switch is inside rotary encoder and just push frequency tuning knob will change:

(band 1) AM (535-1620 kHz)
(band 2) FM (70-108 MHz)
(band 3) SW 2250 kHz
(band 4) SW 3150 kHz
(band 5) SW 3850 kHz
(band 6) SW 4700 kHz
(band 7) SW 5900 kHz
(band 8) SW 7100 kHz
(band 9) SW 9400 kHz
(band 10) SW 11500 kHz
(band 11) SW 13500 kHz
(band 12) SW 15000 kHz
(band 13) SW 17450 kHz
(band 14) SW 18850 kHz
(band 15) SW 21450 kHz
(band 16) SW 25600 kHz
after band_16, frequency will go down to AM again. Actually reception frequency does not have "limit" and more than 30MHz is also covered (I don't know what will be received?). It seems "as far as PLL locks". I did not implement in the code but I confirmed aviation frequency (around 130 MHz) is also covered. (aviation is AM modulation and this radio supports FM only in that frequency, so very small volume voice, unfortunately)

In all cases, battery problem is a headache. When I use radio at bed-side(mostly before sleep), battery shortage is quite annoying me and I love rechargeable one, so I put Lipo charging circuit.

USB terminal is not for programming but just providing charging voltage (5V). During charging, red LED will turns on and,,

Full charge will turn green LED on.

As same as my recent another project, clean PCB is prepared and very limited number (just 3) parts kit is prepared.

Now it is on sale at If you have some interest, please don't miss it!

  • DSP Radio version 3.0 is ready for sale at tindie

    kodera2t09/07/2016 at 13:37 12 comments

    The initial one surely receives from lower frequency to FM broadcast, but some points are pointed-out by great customer.

    (1) Necessity for 3.3 V regulator circuit.

    Rating voltage of KT0915 is 3.3 V but full-charged Lipo approaches 4.0 V. In my experience, KT0915 can work around that voltage but I surely need to use low voltage drop regulator. Actually I ignored existence of excellent low voltage drop (around 0.1 V) regulator and using it radio (KT0915) can work even less than 3.7 V. (Rating voltage of KT0915 is 3.3 V). So I added regulator circuit

    (2) Digital volume control utilising KT0915 function

    Actually KT0915 has "digital volume control", which function can be activated by certain internal register through I2C. Indeed it is surely much more straightforward way than putting ohmic variable resistor for volume control, so I put the function init.

    And this is version 3, including improvement along the comment from great customer!!

    Basically the circuit is same but as we see, some parts are added. Along this modification, I've uploaded new firmware for volume activation for github! As same as previous version, "semi-kit" will be available at my tindie store (after admin of tindie admission).

    In addition, I've received some comment for difficulty of small SMT chip soldering especially LED so..

    I've populated two tact switches, LED, in addition to firmware-written Mega328, KT0915, TP4057 (Lipo charger) and 3.3 V regulator. The semi-kit will be available in the following form.... Stay tune on my tindie store! (not DSP radio version 2 but VERSION 3!)

    Actual operation can be found in the following movie... Have fun!

  • Improved firmware for better AM reception

    kodera2t08/04/2016 at 07:20 0 comments

    Sound quality of AM reception by my original firmware is not so good. (FM does not have problem) Now I uploaded new firmware enables much better AM reception quality.

    Please download the source from github and upload to DSP radio board through FTDI&Arduino IDE.

  • How is "kit" delivered?

    kodera2t08/02/2016 at 01:01 0 comments

    Here I have a small update, showing "How is the kit delivered?"

    The first and last lot (at this moment, one was sold, last two units) is delivered as the picture above. Some chips (ATMega, KT0915, TP4057, OLED) are soldered and the rest parts put on the sheet should be soldered by you for completion. As is described at, this kit does not contain LiPo battery cell (due to international parcel regulation) and please find it at your local reseller. Again, last two unit on sale! If you have interest, don't miss it!!

  • Actual operation movie...

    kodera2t08/01/2016 at 12:39 0 comments

    Here is the actual operation... have fun!

View all 4 project logs

Enjoy this project?



Similar Projects

Does this project spark your interest?

Become a member to follow this project and never miss any updates