Another Raduino Replacement – this time with a Blue Pill

Joe W3JDR is working  on a  Raduino Pill board which is a direct replacement for the stock Raduino, but with an STM32F103 processor and much more I/O. I think it hits all the points on your wish list. I released the PCB to fab a few weeks ago and am waiting for boards to arrive from China. Assuming it functions without major rework, I’ll post the CAD files and Gerbers on my web site and encourage others to develop for it. I plan to immediately mod the stock uBITX firmware to run on it, then will expand functionality to incorporate the work I’ve done with TFT displays, hi-res encoder and software S-meter & AGC. I’ve cleared my bench in anticipation of arrival and am checking the mailbox every day.


Sudden loss of power

Jim Sheldon, W0EB, while prepping a V3 uBITX, he had already built up to give to a friend, all of a sudden observed the RF Power output went to ZERO.

He thought for sure that he’d somehow blown one or both of the IRF510’s, but  nothing is always as it seems.

He checked voltage to the drains of the IRF510’s — ZERO (yes it was hooked up and turned on). Tracing the voltage back, he had nothing on the supply ends of L8 OR L9.  He checked continuity between those same points of L8 and L9 and had good connections there.

He found that he had +12V on the PA Power pin of P1 but nothing on the supply end of L8 which gets connected by a short trace to a very small VIA through the board and a short trace to L8 on the underside.  Looking at the underside, the trace was not burned but it turns out that tiny little VIA was open — possibly from poor plating through the hole.

He put a piece of 30 gauge wire wrap wire through the via and soldered it on both sides. This brought the +12v back to the supply side of L8, L9 and subsequently the drains of the IRF-510’s . After putting it all back together again he now had full power restored.

A few people have observed similar problems with loss of power. This might be the cause in these cases as well, and is definitely worth checking.  There will be no visible indication of anything bad between the PA Power pin on P1 and the rest of the PA circuit.



Do you like those CEC Buttons on this build?

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: