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.

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 …


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.”


Nextion Firmware for 3.2″ and 7″ screens

VE1BWV(Joe) and KN4UD (Allen) have  announced the release of Nextion firmware to support larger screen sizes with KD8CEC firmware v 1.094 and up.

The current releases include support for the 3.2 and 3.2E and for the 7 inch Nextion display.

The screens have been redeveloped with new buttons  and enhanced graphics to reflect each of the 2 display sizes.   This work is on going but due to high requests they have decided to release current versions which are fully functional and utilise the full display area.



Updated Nextion firmware v1.095 beta

Ian KD8CEC has released an update of his µBITx firmware and accompanying firmware for the Nextion display (for 2.4″ and 2.8″ displays).


Others are working on resizing the firmware to work on 3.2″, 3.5″ and 7″ displays.  It would be simple to also convert the 7″ firmware to work with a 5″ display.

So what is new in this latest beta release?

  • The buttons are more reliable, and are quicker to take action.  Changing mode was a bit of a slow process with lots of flashing buttons in previous versions

  • Pressing on the step size now opens up buttons to select step value.  This makes it so much quicker to get around the band.  Select a bigger step value to get to where you want to go, and switch back to 1Hz steps to fine tune.


  • By selecting which file you download, you can now read/write to all EEPROM memories or just those that relate to the Nextion display, protecting your rig’s settings securely if you want (the only way you can change them is in uBITx Manager if you go with this option).

  • Adjust the frequency by pressing on different sections of the frequency shown on the Nextion display
  • The lock button locks the Nextion screen as well now which is handy for using your rig around young children.
  • The sleep function has been improved.  You can wake the screen up by moving the encoder dial, or pressing on the bottom left of the screen.

  • Install two screens – they will each mirror what happens on the other, but in some modes different functions can appear
  • A number of enhancements to the control menu, including an elementary spectrum scope, band scanning and memory selection, saving.

The pace of development is pretty staggering.  We all look forward to other functions being added to the Nextion screen in future!

To download these beta files check out Ian’s article.

Analogue S-meter using a VU meter and driver module

Jean-Luc F6HOY added an analog s meter to his first BITx40 with a simple circuit on an audio line and a 500 microA vu-meter.  All was fine except that without any AGC it only provided an indication of the signal level.

Jean-Luc added a Chinese Audio Vu-meter that is much better on his µBITx.
For around 15€ he received a circuit module and 2 vu-meters.   Only one vu-meter is used of course.   The circuit board functions as an AGC, and for an extra bit of fun he has a nice warm light in the shack from the yellow light of the VU meter.

You can get this kit from several shops in China (one such  example).