Differences between the JackAl and Nextion displays

Most people don’t understand and won’t want to understand the differences between different types of display technologies.

Unfortunately,  the µBITx community has fractured its user base amongst competing screen technologies.   There are many different types of LCD display screens and they are not compatible at all.   

Differences between the Nextion and JackAl displays have been discussed on the BITX20 IO Group list following discussion about whether a Nextion screen used with the KD8CEC firmware could be ported across to the JackAl.  The simple answer is “No”!

Brian N8BDB notes that  it’s not going to be as simple as replacing a driver and rebuilding the application.  The Nextion display works in a very different way than the normal displays most people use for microprocessors like arduino and teensy.

Normally the display is a “dumb” device that just handles displaying the dots.  Software libraries are used to provide basic functionality like drawing lines, boxes, and text.  Touch events are handled completely separately by other libraries.

The Nextion display is the opposite.  The display has it’s own microcontroller, memory, etc. and the arduino communicates with it through a serial interface.  All of the buttons, text, gauges, etc. are prebuilt in the Nextion editor.  The application doesn’t know where they are on the screen.  It just has a name such as “button1” that is associated with a button on a particular screen for instance.  The application just sends a command to the display to change the text of “button1” to “abcd”.  It would require a significant rewrite of the JackAl UI code to make it work with a Nextion display.

The other thing as Jack pointed out is about resolution.  The Nextion displays most people have are much lower resolution than the display used by the JackAl board.  The 2.4″ and 2.8″ Nextion displays are 320×240.  The 5″ Nextion display ($60) is the closest one with similar resolution (800×480) and that is 33% more in price than the display ($40) that JackAl currently uses.  Even the 4.3″ Nextion display is only 480×272.

There are pros and cons of both screen types.  The Nextion costs a bit more per pixel because it has a processor on board, but the demand (in terms of memory and processing power) on the main µBITx is minimal.   The processor and screen communicate using a series of codes.   The Nextion (in theory) can be adapted to have quite different user interfaces for the same functions.  There are, in fact, at least two distinctly different versions of “look and feel” available already.   However, setting up these requires a fairly steep learning curve on the screen management environment.

On the other hand, the JackAl screen (along with all other types of LCD screens) is strongly tied into the firmware of the JackAl teensy processor and amending the “look and feel” of the display requires detailed knowledge of the processor, firmware and the screen programming environment on which the JackAl is built.  It is unlikely that the Nextion will be ported across to the JackAl environment any time soon.  Bite the bullet and buy a new screen!


Should you build your own?

David Balfour says there are a number of hams who should not buy a kit!

The main boards are factory tested, but even simple things seem to trip up many. A Man has to Know his Limits.

He says he is lucky to have purchased two ubitx radios that were not working or fried. Neither had much going wrong except the original owner didn’t have a clue as to what they did wrong. He didn’t even need a VOM to fix either of these kits.

David thinks some hams are born appliance operators. He has a spare ubitx but would hate to sell this to someone who doesn’t want to get some worn out electrons under his fingernails.

The photo of his rig (above) suggests he has a few talents!


Cheap DSP for a QRP rig

Earlier in the year Giuseppe IK8YFW shared a project he has been working on to make a cheap and simple DSP receiver based on the arm cortex stm32f103 processor.  This  module costs less than two US dollars in Far East online shops.

He has implemented two narrow CW filters of about 300 and 700 Hz and two SSB filters with widths of less than 2200 Hz, and less than 3300 Hz.  He also includes a 6-level noise reduction algorithm.

The project is a very cheap solution and is suitable to embed in every QRP project. Details of the project and code is available on github.  It is still at an experimental stage but is worth looking at by experimenters.

The project can be found here:


Some test videos of the DSP in action can be found here:




Microphony in your uBITx

Peter G8FWY had a problem with his µBITx.  It picked up sound from touching the case and pushed this through his headphones.

If you have a similar problem it is most likely to be ceramic capacitors in the audio stages of your rig.

In this case it turned out to be C50 in the audio pre amp.  Peter replaced it with a leaded electrolytic capacitor and the problem went away.


Jackal Board for the uBITx released

Jack, W8TEE and Al, AC8GY have announced that QRP Guys is ready to take orders for the JackAl support board for the µBITX. A link to a list of its feature set, a video of it in action, and some photos can be seen at


Note that the AGC implements both audio and IF AGC. The appendix to the manual shows a plot of its characteristics. DSP filters are available, including user-defined filters (CUST in figure below). A CW keyer and decoder are also included. The main screen looks like this:

The decoded CW can be seen along the bottom. (In all honesty, that is a guy sending almost perfect code at about 22wpm.  Jack is still playing with the decoder and expects some really smart user to make it much better. It’s got real possibilities as it is based on the FFT bin counts.)

QRP Guys is offering the JackAl board for $40 for the first 50 boards.

After those are gone, the price will be $50.

Shipping in the CONUS is $5 and DX is $15. This is what the JackAl board you’ll get looks like:

The board has all of the SMD’s mounted (including the Si5351 and the display buffer IC). The user does have to supply additional parts: A Teensy 3.6 and associated audio board (both from PJRC.com) and either a 5″ or 7″ TFT touch screen display (BuyDIsplay.com). You should also consider case size when you select your display size. (Note: BuyDisplay.com has actual sizes for each display and they are measured like a TV, so the case can be smaller than you think.)  If addition, there are some IC’s, connectors, audio isolation xfmrs, and header pins that most of you will want to add. The cost of these additional parts should be less than $15 depending on your junk box. The board with these in place looks like this:

The connectors are not required but, since you are also give about a dozen free I/O pins for experimenting, you may want to add them. (The yellow pins above are test points.)

The assembly manual can also be found on the website.

This is an intermediate to advanced semi-kit project. Our intention is to not only give the µBITX additional capability, but to serve as a platform for experimentation, which we hope you will share with the rest of us. You will have approximately 700K of flash and 200K of SRAM free for your inventive side to exploit.

Al and Jack already have some (software) extensions we want to implement. Note JackAl does NOT fix the harmonic or spur issues. However, our test µBITX’s right out of the box were well within spec for 80 and 40 meters and spot on for 20M (15M and 10M, not so much). If you have doubts about your µBITX, check it out. It could well be that your favorite band is within spec. If you don’t have a spectrum analyzer, check with members of your club or the physics department of your local high school,. junior college, or university. Most will be glad to help.

You need to provide your own Teensy.  The reason for ordering a Teensy without pins is that you will need to use header sockets with long pins on the Teensy so that the Audio shield can plug into the Teensy and the Teensy plug into the JackAl board. The Teensy pins do not have the header sockets and are difficult to change without damaging the Teensy.

Note that the power jumper on the bottom of the Teensy 3.6 also has to be cut.


A chronology of mods

Dan W2DLC ordered his µBITx on December 29, 2017 and received it on March 2, 2018.

It was a version 3 with the WX branded TDA2822 audio chip.

(1) By the time he was ready to assemble it, Ron, W7HD had posted a fix using a voltage regulator.  This was his first mod and he has had good working audio since then.


(2)The second mod he implemented was installing the KD8CEC firmware which was more intuitive for me and solved some issues such as keying responsiveness.


(3) The third mod was to add a short USB cable from the Arduino Nano to allow data access outside the case.

(4) The fourth mod was adding the click-pop suppression kit from Don ND6T, Wayne VA7AT, and kitted by Kees K5BCQ.



(5) The fifth mod was the RF output peaking mod suggested by Howard Fidel WB2VXW



(6) The sixth mod was the ND6T AGC kit that he got from K5BCQ at the same time as the click-pop kit.  When he installed the AGC kit, he used Kees’s installation suggestions for mounting it on the main board.  He also added an RF attenuator/gain control as suggested by ND6T, and hooked a wire from J1 to the purple analog wire on the Raduino to provide an S meter.


(7) While he had the board on the table, R250 was changed to 100K to reduce the sidetone level and C1 cap was replaced with a 1μF to shape the CW note.


(8) Then  the relays were changed out for  Axicoms  as suggested by Mike W0MNE, to reduce harmonics when using SSB on the lower HF bands.


(8) Finally, he replaced L7 and L5 with SMT inductors as suggested by Raj VU2ZAP to reduce spurs on the higher HF bands.


Dan is very happy with how well my uBITX functions at this point.  He has placed it in a small Apache case behind an aluminium faceplate that he fabricated.  The whole thing is pretty rugged and works well with a three cell 18650 battery pack.

Dan says he finally has the spy radio he has always wanted.

Overall Reference 

Antuino under design

Ashhar Farhan VU2ESE and designer of the µBITx has announced that he is working on a new kit – the Antuino.

The PCB version of the Antuino (The Arduino based Antenna Analyzer) is still under development, but we will all be looking forward to its release.