Thursday, April 25, 2024

Trying a $15 70cm transceiver HK-188

Peter, VK3YE, recently posted a video of a pair of 2.4Ghz transceivers he bought at Aldi for $20. They worked OK but had a number of obvious annoying problems including a lack of a display. 

Browsing Amazon I noticed a pair of 446MHz transceivers for $30 and I wondered what you get for the extra $10.

As you'll see in the video, they work very well, and I'd have to say the extra $10 is well rewarded. (Of course you don't have to spend much more to get a Quansheng radio!)

The radios are on 446Mhz, which is in the Amateur 70cm band so Richard and I are licensed to use them but I'm not sure how legal they are for the general public.

The manual is on the FCC website here. The biggest chip on the board has no label and is presumably the CPU / SOC and drives the LCD display.

I can see some inductors in the output presumably for low pass or antenna matching - a good sign. Components I can read are:

  • WX050 D812 4 pins
  • 26.000MHz crystal
  • BEKEN BK4818 BS3432FB 32 pins 
  • 4VZU 5 pins
  • M4890S UDE399 8 pins
The BK4818 is a half-duplex TDD FM transceiver.

"The BK4818 is a half duplex TDD FM transceiver operating from 115 MHz to 537 MHz band for worldwide personal radio. Besides speech communication, the BK4815N on-chip FSK data modem supports F2D and F1W emission to be used in FRS band for text message and GPS information exchange.

The BK4818 is a complete, small form factor solution optimized for low-power, low-cost, and highly integrated mobile and portable consumer electronic devices, requiring only a few external decoupling capacitors and an external inductor for input matching.

- World wide band: 115 ~ 537 MHz
- 12.5/25 kHz channel spacing
- On chip 5 dBm RF PA
- 3.0 V to 3.6 V power supply
- CTCSS tone receiver with up to parallel eight frequency detector
- 23/24 bit programmable DCS code
- Standard DTMF and programmable in-band dual tone
- SELCALL and programmable in-band single tone
- 1.2/2.4 kbps FSK data modem with either F2D or F1W modulation type
- Frequency inversion scrambler
- Voice activated switch (VOX) and time-out timer
- RF Signal strength measurement and signal quality measurement
- TX Audio signal strength indication and RX audio signal strength indication
- 3-wires interface with MCU with maximum 8 Mbps clock rate
- QFN 4x4 32-Pin package"

Quite a capable device.

This seems like a more sophisticated device than the Aldi one that Peter, VK3YE, reviewed.

(Image taken from VK3YE's video). The HK-188 has an LCD display which would add some complexity but not as much as I see in there.


  1. RE CPU/SoC: Hmm, there are ISP pads on that!

    The LQFP48 made me think it was a STM32F103 (or near), however its RST on pin 38 rules that out.

    Oh well, a JTAG probe would find out.

  2. Oh? Please tell me more. You think those round pads are for in circuit programming?
    What is RST? (reset?).

    The BK4818 says it has three wire interface to the MCU, would that be I2C?

  3. There's RST/Reset, PCK/Clock, PDA/Data, VCC, and GND pads -- just like that used for ISP by a number of products. The MSP430s have a "2 wire JTAG", ST's STlink uses the same wires...

    SPI I would say for the BK4818 - found the datasheet for the BK4819, assumely a similar device with a different frequency range ( and like the majority of peripheral ICs uses it.

    I've just found a mention on Twitter that the MCU is a "DG32F030" - an ARM Cortex M0 variant:

    Ha. These $15 radios can very likely be reprogrammed! :D