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Introduction to UV-K5 HF Fullband receive version 0.3

Introduction to UV-K5 HF Fullband receive Version 0.3

This is an introduction to UV-K5 HF full-band reception firmware 0.3HF using SI4732-A10.
This version is released separately from the existing UV-K5 CEC firmware version. because space is needed to store a large PATCH file to use SI4732-A10's SSB.
0.3HF added several functions to use SSB for shortwave radio and amateur radio.

1. Basic usage
1.1 HF Receive 
Press and hold button '0' (FM radio) to switch to HF reception mode.
Click the Exit button to end. 

1.2 Mode change
In HF reception mode, briefly press F to switch between AM and FM.
(FM broadcasting does not have good reception because an antenna is not connected. However, it is still audible through the connected AM (SSB) antenna.)

Press and hold the 'F' key to switch to SSB mode. In SSB mode, briefly press 'F' to select LSB and USB. The basic usage is the same as Version 2.0.

1.3 Modification example
Below are photos of PA2JSA's modifications.  He sent me a photo and gave me permission to post it on my blog.

It is said that the 3Khz incorrect frequency specified in the picture above was solved by changing the CAP connected to the crystal to 10pF.

1.4 News
Several radio amateurs are designing PCBs.
In particular, we are trying to make DIY easy with PCBs of 0.15mm or less. I can't post it yet because I don't have permission, but I will share my test results in the future.

2.Introduction to displayed items
2.1 In the picture below, item A is the frequency and mode currently being received.
Item B is BFO. 
The SI4732-A10 chip is a low-cost chip ($2~3) that can receive SSB, AM, and FM
However, the minimum frequency change unit is 1Khz
However, it can be adjusted in 1Hz increments by changing the BFO.
I tested this and verified that it also changes the filter passband. If you want to finely change the frequency below 1Khz, change the BFO. You can use BFO as a fine tune. Naturally, BFO can only be used in SSB. The BFO change unit is fixed to 5.

EX) 14.050.080Mhz
      Main Freq : 14.050, BFO 080

2.2 Displays the band of the frequency currently being displayed.
I combined the bands used in conventional shortwave radio with those used in amateur radio. To eliminate empty frequencies, we increased the range of the band little by little, and in the process, it became a little different from the band we know. However, there will be no major inconvenience in using it.

Item A scrolls according to frequency. The underlined part of the band name is the current band. In the picture below 20M is underlined
Item B indicates whether it is a HAM band or a shortwave broadcasting band. There are some errors. (For example, classify the HF CB range as the HAM BAND)

2.3 Signal meter & rssi, snr values
Signal display follows the standard from S4 and above.
Reception exceeding S9 is displayed from +1 to a maximum of +20dB. The maximum is +20dB

3. Frequency change, change of various values
3.1 To change the frequency, use the UP/DOWN buttons as in the previous version.
Starting from the 0.3HF version, the frequency change steps support 1, 10, 100, 1000, and 10000 Khz and are underlined at the bottom of the main frequency.

3.2Starting with version 0.3, values can be changed using only UV-K5's menu button and side switches (two switches below PTT).

Part A refers to the value that changes when the SIDE key is pressed.

When you press the menu button('M'), the selection changes as shown below.

The current value of the selected item is displayed below.
In the picture below, the BAND item is selected and the current value is 20M band.

In the picture below, part A currently displays each item.
I put it in small letters because it's not that important. If small letters are difficult to read, press the M button and look at the bottom line. 

For example, let's change the steps.
Press the 'M' button to change the selection to STP (STEP)

Currently it is 1Khz.

Press the side key UP to change to 10Khz

For example, let's change the band.
Press the ‘M’ button to select BND (BAND)
Current Band is 630M

When you press the SIDE Down button, the band below it, L.F., is selected. (I don't think anyone uses it and I have never used it, but since SI4732-A10 supports it, I added it to the band)

You can move to the desired band by pressing the SIDE UP/DOWN keys as shown in the pictures below

Only some of the values set by the user are saved in eeprom when the user exits by pressing the Exit button. This is because integration with other versions has not been decided.
If the address of the eeprom to be used is determined before Version 1.0, most of the values selected by the user will be saved in the eeprom.


Download and use CEC_03.HF.packed.bin from the link below.


  1. Can I use the SI4735GMR (QFN) chip? I designed a PCB to easily replace the IC, with only a REST jumper needed.

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  2. Having issues after doing this mod - no RX, and locking up after button presses. Touching a leg of the Xtal restores RX, but no audio or signal from a Signal generator. i think my Xtals are poor quality (old watch xtals i had) so i am waiting for some newer ones to try again. Can You clarify the workflow for this mod? the PA2JSA pictures show all the components in the area have been removed, but the photo shows them still in place - which should it be? A higher resolution picture of the finished mod would be good also. Firmware .2 and .3 have no issues, but the hardware is clearly not right for me so far. (Orange Display radio, with USB-C)

  3. I've uploaded some videos on youtube of a modded K5. Search my channel (IU3POA). Thank you KD8CEC for your wonderful work. 73!

    1. This comment has been removed by the author.

  4. Maintain your commendable efforts; your work is highly appreciated. view now

  5. Your work is very interesting and helpful. You done a great job..
    do my classes

  6. It would be great to have the ability to use chirp to edit memories

  7. Keep up the good work ! - what about adding the FM Mode of the si4732 also ?

  8. I did the mod using the aliexpress board, but I have a few questions. Why do we need to change the choke on the antenna input with the aliexpress board to I think it is a 100 uh rf choke. I could be wrong on the value but please correct me if I am wrong. What is the reason to change the default choke in the radio. Also I noticed that in USB or LSB mode, the audio volume is way lower than in AM mode. Is this normal? Please if anyone can answer the question, I would appreciate it. Keep up the good work, I am super impressed with all the work that has been done. Very impressed. Thanks everyone for all the work.

  9. This blog stands out for its wealth of information; the depth of insights is impressive.

  10. Has any one try a newly designed board with audio amplifier for low SSB, redisigned HF and FM bandpass filters and more?


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