Important  Information provides help for constructors:  Preventing catastrophes and providing guides, fixes and modifications for your µBITx.

CAUTION : If you power up the µBITX without the pull-up resistor the µBITX can randomly go into CW transmit. Have you installed the 4.7k pullup to 5v on the CW key pin?

v3 Board?  – There are known issues with WX brand TDA2822 chips (U1): Read this.  Earlier UCI and socketed TDA2822 are not affected.

v4 Board? – If your audio is distorted see this article.  It is too early to determine yet whether this problem is widespread or is limited to just a few kits.  Note that audio output is reduced over the v3 board.  If you use a low impedance speaker you may need an additional amplifier module (LM386, TDA2822, etc.) to get adequate volume.   The pop mod is not required.

Do not overdrive your rig on SSB or digital modes above 18MHz.  This may cause spurs exceeding US emission requirements.  Read this post for details.

SHIPPING:  µBitx orders have been shipping within one or two working days of being ordered. You should receive a shipping notification through PayPal once your product has been shipped. Estimated delivery times to different countries:

EU:         IndiaPost: 2-5 days  DHL: 2-5 days
US:         IndiaPost: 10 days     DHL: 2-5 days
Asia:      IndiaPost: 2-4 days   DHL: 2-4 days
AU/NZ: IndiaPost:10 days      DHL: 5-7 days

BITX QSO DAY:   Every Sunday – 3PM & 7PM Local Time – 7277 kHz in North America, 7177 kHz elsewhere.

New builds with Nextion display

Malcolm EI8FH says, “Many thanks to Ian KD8CEC and Allen Merrill for their great work and time in producing superb operating software and display for the ubitx transceiver , very much appreciated.”


Nextion 3.2″ and 3.5″ Display Firmware

Allan KN4UD has put together display firmware for the Nextion 3.2″ and 3.5″ displays that represent “works in progress”.



Replacement to Q70 for more audio gain, less overload

Tom W1EAT  has noted that Q70, the audio pre-amp, has a really big job in the uBITX and sometimes gets overdriven by very strong signals.   Tom also replaced the 2822 audio amp with an LM380 and lost around 8db in audio gain.

So he though he would try another transistor to try and improve this situaiton.

He had some 2SC945 transistors marked with the highest “beta”(AKA hfe) rating, so I took one with a 360 hfe and replaced Q70.   He made no other component changes. The 2SC945 is supposed to be specially designed for audio pre-amps, so it ought to be a good replacement.

With RX voltage of 13.6, the Q70 collector voltage is 4.67 on the 2sc945.

I should mention that I added a 16K resistor from the base to ground when Q70 was a 2n3904, which was suggested by W3JDR to reduce distortion. I did not remove that resistor.

The results were totally positive. Tom has more AF gain, and none of the signals in tje IARU HF contest overloaded it.

Something for experimenters to try out …


Nextion 5″ and 7″ TFT and HMI files

The effects on the new 7″ Nextion screen design from VE1BWV are pretty impressive!   You need a large enclosure to enjoy the 7″ display.

Photo courtesy of Vern AA7HC


Coated up

Liviu YO5QCD has completed his µBITx and it looks very attractive!
It was completed a month ago with the goal of having a portable/mobile HF field day/emergency station setup.
He has since built an AGC add-on. Liviu believes this is a big “must”. He home-brewed it using the ND6T schematic.
For field work he has built a minimalist L-match for use with a random wire at just a few meters above ground.   He is building an SWR-meter, but this is not yet finished.
He is now running CEC software  and wants to complete the SWR-meter, add a 20×4 LCD, incorporate an audio CW filter and a speech processor.
In the first month of testing at the home QTH (using an OCFD antenna that works on  80-10m) Liviu has:
  • worked all YO districts on 80m, with a consistent 57 received (max. distance covered about 500km)
  • worked on 40m and 20m: ER, UA, I, DE, ON, SV, 7X with an (overall) RS of 44 to 58 (about 1800-2000km)
He has his hopes up after several hours in field testing and a contact made 180km away on a random wire about 15m long and with no matching unit.
Liviu says ” I’m really delighted with this little gem!”

Some great mods from PH2LB


Lex PH2LB  wrote to to tell us about a page on his website where he describes his uBitx (V3) mods.   This is a very nice build, and he has some good ideas.   Check his page out here

In particular Lex has developed some custom firmware that firmware geeks may be quite interested in …

“Second mod : custom firmware”

Originally based on the v2 software but merged to v4.3 and updated to code to have a lower RAM footprint (usage of F(…) macro and strcpy_P) with about 50%.

Source files can be found here :

Over the last few months there have been a range of ideas to boost mic drive output or to add compression.  Here’s a mod designed to work with a dynamic microphone …

“Fourth mod : dynamic microphone amplifier.”

Because I like to work with dynamic microphones, I added a dynamic microphone amplifier based on the microphone preamp designed by Javier Solans Badia, EA3GCY for his ILER transceivers.

There are a whole bunch of ways to add buttons. KD8CEC does this through paralleling up buttons with different series resistor values on the encoder analogue port).   Lex has taken a different approach that will be of interest to some constructors.   He uses a PCF8574 I2C encoder (like the backpacks for a 16×2 or 20×4 LCD display) and uses the existing I2C bus…

“Fifth mod : again adding extra buttons.”

Using a PCF8574AP I2C IO Extender and hooked it up to the all-ready existing I2C bus on the Raduino for more direct menu buttons. Needs the custom firmware to direct switch between bands with a PA bandplan limitation (also has FULL option) and Step size up and down.


Something that a number of constructors have done is to remove the 7805  and supply 5v to the Raduio using a separate 5v supply.  Most are using buck or buck boost modules, but Lex has used a P-MOSFET.   There’s a good description of his approach on his website …

“Sixth mod : removing 7805 from Raduino and reverse power protection.”

Relocating the 7805 is a good idea, but adding a reversed voltage polarity to a uBitx is a must. I used a P-MOSFETs for that (also link to good video about using P-MOSFETS for reverse power protection).

Finally, you may be interested in Lex’s use of the Manhattan style technique for PCB layout.  It can look very professional as per this example:

Nextion display 3.5″ beta firmware files

Ron, KGØJ has done some work on rescaling the graphics for the Nextion 3.5” display.   It’s not 100% complete yet but he’s got all the major functional screens done and he has started work on moving some of the others around so they at least use some more of the screen real estate.  Ron says the rescaled graphics look better than earlier versions.

The files are attached as a zip containing the .tft and .hmi files.  The 90 refers to the orientation of the display, this one puts the SD card slot at the bottom.

Latest firmware release v6.00R for BITeensio

W0EB and W2CTX have just completed and released a powerful new set of firmware for their BITeensio card.

Details about the BITeensio and links to the firmware can be found on the website at

Release Announcement

“As of this morning, July 8, we have released a powerful new version of the firmware for our BITeensio card, V6.00R, that utilizes the Teensy 3.6’s capability to utilize USB “Host” mode  and connect a standard USB ASCII keyboard (many wireless ones work too).  PJRC (the people that make the Teensy ) offer a standard USB cable thatcan plug into the Teensy. (You do have to add a 5 pin header to the Teensy 3.6 board) on the same side, and just to the right of the USB “Micro B” connector into which you will be able to plug the standard USB 2.0 cable.  The red wire (+5V) must be plugged into the pin indicated by a white square in the outline on the Teensy 3.6.In this version, we have implemented a comprehensive command list that allows many of the standard “menu” commands, including the operating frequency, to be entered using the keyboard.

“Also included is a brand new Keyboard CW keyer that uses most of the K1EL keyboard keyer’s character/key mapping.  The V6.00R firmware is released as pre-compiled “HEX” files and placed in the appropriate directory of the “Files” link on the website.   We are not denying anyone that wants it the source code, but you will have to ask for it with the understanding that if you cannot compile it or if you modify it, you are on your own as we just don’t have time to troubleshoot it for you.”