A serial connection from your uBITx

Sascha DL5SMB has soldered some wires to D0 and D1 (RX + TX) and ground on the Raduino nano and then installed a MINI-DIN 8 socket to the uBITX like in an FT817.

“Why?” you may ask!   He is  building a  TF3LJs Magnetic Loop Controller at the moment, which communicates with the transceiver via CAT for tuning the antenna. This interface uses just these three lines. So he needed to make them talk 🙂

After a few hiccups, and a helpful suggestion from John VK2ETA, this solution has now been made to work.   The idea of using D0 and D1 connections on the Nano is to provide a separate serial feed to the Magnetic Loop Controller that is independent of the CAT signals coming out of the USB socket.   This may be a good solution for other potential use cases as well (e.g. driving automatic tuners).


(Yet another) Raduino replacement board

Jim W0EB has produced (yet another) drop-in Raduino clone, available in kit form, for anyone needing a replacement for a damaged Raduino that they are otherwise unable to repair or if they are just wanting to have a spare on hand.

It’s being offered as a bare board, a complete kit of parts INCLUDING the NANO which will be pre-programmed with Ashhar Farhan’s latest factory software from Github (Currently v4.3) or, for a slightly higher price, the kit version is being offered with the Si5351 already soldered in place and continuity checked to insure the connections are good and there are no shorts between the pins.

The new card has some extra bypassing capacitors.  The 4.7K CW pull up resistor can be directly mounted on the board (or if you are replacing an existing Raduino installation and have already wired it to your key jack you can leave it off the board).

The 7805 regulator has been mounted flat on the rear of the board with a heat sink and input dropping resistor so that it runs much cooler.

The clone is just over a centimeter wider than the original, but the display mounting holes have been kept to the exact same pattern.  A standard 16 X 2 parallel display will mount properly.  The display is not supplied with the kit to keep the cost lower as most users already have one or more on hand anyway.

The pre-programmed NANO  will be supplied with the pins loose and not installed so the user can mount it either on the front (not recommended) or on the back of the card to keep it out of the way of the display in the manner of the current factory supplied Raduino cards.

Any software that currently runs on an original Raduino will run on this card including the KD8CEC versions.  (That includes CEC’s Nextion enabled versions as well).

The construction manual, pictures of the board and ordering/availability information can be found on Jim’s website.


Nextion display and a second arduino

Ian KD8CEC has now given us part 2 of his description of the latest firmware update (v1.097).   If you have a Nextion display, and add a second arduino you can have a higher quality s-meter and multi-band signal monitor on your µBITx.

For more details go to Ian’s website at hamskey.com

The wire up diagram follows:

The second arduino echos information in one direction from the main raduino via the i2c serial channel which is faster than via serial port.  It uses a dedicated serial port to output the signal again, potentially making the sampling faster for taking signal strength readings.  It will be interesting to see what effect this has in practice.

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.


Some great mods from PH2LB


Lex PH2LB  wrote to uBITx.net 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 : https://github.com/ph2lb/ubitx4

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:

Reasonable heat output and the raduino regulator



Bob W4GHV asks how hot the regulator on the Raduino should get.

The Raduino has a 7805 regulator sticking awkwardly out of the side of the Raduino board.  Unsoldering the 7805 regulator and mounting it   on the reverse side of the board (facing inwards) can fix that little awkwardness.

The regulator also has another problem.  It gets hot!  It is fed with 12v DC input from the rig and produces regulated +5V for the Arduino Nano and the 16×2 Display unit.   The display itself draws up to 100mA.  The Nano typically draws around 35-70 mA, but it depends on exactly  what is connected.   The voltage difference between the input and output multiplied by the current is power dissipated in heat in watts (i.e. typically a bit over 1 watt).

The 7805 regulator can feel quite hot to the touch.   However, there is really no danger that it will get overheated at 12 to 13.8v input voltage and typical current draws from the Raduino unit.  Allison KB1GMX says however, “Keep it under 70C (168F) as the device has a thermal shutdown and it lives longer”.

You can share the heat around by installing a resistor between the 12vDC line and the 7805 regulator input. Skip, NC9O, added a 47 ohm resistor in the 12vdc into the regulator by cutting the trace from pin 15&16 on the Raduino. He used a  1/4 watt resistor, but calculations by others suggest a 1/2 watt or 1 watt resistor would be better.

The alternative is to remove the regulator altogether and feed the Raduino from a suitable 12v to 5v buck power supply (obtainable off eBay or Aliexpress for very little outlay) or set the output of the buck power supply to just over 7v if you can’t be bothered removing the 7805.    For those of us thinking about touch screens, this makes quite a bit of sense!


Biteensio production boards have arrived and available now

Jim  W0EB has announced that the Biteensio production boards have arrived and been checked out.  See www.w0eb.com for details on how you can order one of these.   Remember that Vince K8ZW was the winner of the competition to name these boards.

Jim also has some breakout boards for the 1/8″ jacks that will allow them to be easily mounted and wired up without having to guess which terminal does what.  These may save a lot of grief.

Key features of this board include:

  1. uses the PJRC Teensy 3.6 as the MPU rather than the Arduino NANO
  2. plugs into the 16 pin female header on the uBITX main board just like the Raduino and the RadI2Cino
  3. the main tuning encoder, function switch and push-to-talk wiring will still be compatible with both the Raduino and the RadI2Cino.
  4. All of the extra, available I/O pins are brought out to DuPont pin headers (some on the front and some on the back of the board)  

See the board installed on the µBITx main board below:


Prices are $12 (USD) for the bare boards to domestic US customers and $16 (USD) to international customers.

Kits which will include all parts except a Teensy 3.6 MPU, will be US$35 to US customers and US$45 to international customers. This price includes shipping (both domestic and international).

PayPal will be the preferred payment method and the ONLY payment method for international customers.

Download a copy of the BITeensio Board Construction Manual. Up to date versions will always be available in the “Documentation” directory under the W0EB/W2CTX uBITX Files link on this page.

For other details see the W0EB website.

Note that the Biteensio is not compatible with the manufacturer’s firmware supplied with your µBITx or the CEC firmware from Ian KD8CEC. The Biteensio board uses a different keying system and a different processor (Teensy 3.5 or 3.6), so you will need to use the W0EB/W2CTX firmware supplied especially for the Biteensio.


Quadrature output from si5351a

The SI5351a is a key secret to the success of the BITx range of transceivers.  This chip puts out three PLL signals for the two local oscillators and the VFO in the µBITx.   Without this chip (or something similar) a double superhet design such as that used in the µBITx would require considerably more complexity, with either an analogue VFO that was prone to drift (as in the BITX20) or a PLL circuit that added cost and complexity.  The Raduino integrates a 16×2 line display along with an arduino nano and the SI5351a chip … prebuilt for US$25.

So along comes Miguel PY2OHH who announces that he as designed a new
VFO using the SI5351 and Arduino nano, which produces an output  “in quadrature” from 4.76 MHz to 220MHz.  This means is has two outputs on the same frequency, but which are 90 degrees phase shifted from each other.    Note that there is also a small frequency window that can’t be used between 144.66 MHz and 150MHz.

You can read all about the idea, and see a prototype VFO here.

So why is this such a big deal?

What you may not know is that a quadrature mixer, which requires two signals from a local oscillator fed at 90 degrees from each other, is at the core of most SDR receivers.   In an SDR receiver, there is very little “front end” analogue circuitry, with signals rapidly routed to a processor in digital form to apply filtering and band-limiting.    Miguel’s breakthrough paves the way for simple, low-cost SDR transceivers that are of low cost and high performance.   We know that Ashhar Farhan VU2ESE has said in the past that he is experimenting with SDR designs (and with a VHF/UHF version of the BITx).   Let’s hope this innovation spurs him on to produce a stunning new SDR design in kit form!