The uBitx

This page describes my building of a uBitx transceiver, designed by Ashhar Farhan. Additional information, including ordering information, may be found on

The HF Signals site.

Along the way, I made a number of changes (improvements, depending upon who you ask) to tailor it to my specific tastes. I also used a number of components, in these changes, I had on hand.

It is worth noting the uBitx is a transceiver platform. As such, the builder will need to provide a number of items to actually complete the uBitx. The primary items are a case and knobs for the controls. Although the uBitx will generally operate just fine spread out on a suitable build surface.

The starting point

The uBitx has proved to be a very popular platform. The uBitx, unchanged from the original design is a fairly capable transceiver. However, being a platform opens up a tremendous number of choices:

Type and style of a case: from none at all, to what ever you have around (a school lunchbox for example), to commercially available project boxes, to 3D printed enclosures (which may require additional shielding).
The types of knobs used for the ON-OFF-Volume control and the Tuning control. While the tuning encoder shaft is a common 1/4 inch (or 6mm) the ON-OFF-Volume control has (I believe) a 5mm shaft. This is not an overly big issue, but it is something of which you should be aware.
The type of display: the original 16x2 LCD display, a larger 20x4 LCD display, or even a TFT touch screen display (of just about any size).

My Platform Modification Choices.

As I said, I had a number of changes I wanted to make to the basic platform:

I had a Hammond 1426O-B case, so I decided to use it for the uBitx.
I used some fairly traditional pointer knobs (CED K370 and K374 from eBay).
Becausse of my choice for a Volume control knob, I had to change the volume potentiometer to one with a more standard 1/4 inch shaft.
Because the potentiometer I had did not have an ON-OFF switch, I added a small toggle switch (for power) and an LED (to indicate power was on; a bit redundant as the display could serve the same purpose). Later I found an NTE 502-0311, which is a 10K Audio taper potentiometer with an ON/OFF switch.
Separate fuses: one for the PA semiconductors and the other for everything else.
A USB connector on the back panel.
An Adafruit 2050 3.5 inch TFT touchscreen display.
A Meduino Mega2650 Pro Mini controller board.
An Adafruit 2045 Si5351 Clock Generator board.
An additional 7805 voltage regulator and buss.
Insulation between the PA FETs and their heat sinks.
A socket for the TDA2822 audio amplifier chip.

Mechanical Work

The first set of tasks were to do all of the required mechanical work. This allowed the electrical work to be done as required cable/wire lengths could be determined.

Here is an example of the layout technique I used for making all the necessary holes in the project box. I covered the panel with (easy to remove) masking tape and then used a pen to mark the locations.

Here is the completed front panel with all the necessary holes drilled and the opening cut for the display.
From left to right, the opening / holes are for

A large rectangular opening for the TFT display.
Holes for the key, microphone, and headphones. (I haven't yet settled on the order.)
A hole for the volume control.
A hole for the tuning encoder.
Holes for the power LED (top) and power toggle switch (bottom).

Here is the completed rear panel with all the necessary holes drilled.
From left to right, the holes are for

A hole for the BNC antenna connector.
A hole for the PA fuse.
A hole for the main board, display, Mega2560, and Si5351 boards.
A hole for the power connector.
A small hole for a mini-USB connector.

Here are pictures of the Mega2650 and Si5351 boards mounted to the top of the cabinet, the rear panel with all the hardware mounted, and the front panel with all the hardware mounted.

Here is the uBitx main board mounted to the bottom of the cabinet. While not shown in the above pictures, the front and rear panels had to be notched to allow room for the standoffs used to mount the uBitx board.

Here is the picture showing the uBitx board mounted and the front and read panels mounted. This will give you an idea of the layout.

Because there are a number of new boards requiring 5VDC power, I decided to not only add a bit of internal shielding but add a separate 5VDC voltage regulator and distribution buss. I used a two row header with plus on one side and minus on the other. This is very convenient for using two pin headers to the various new boards.

Here is the picture showing the side of the shield facing the uBitx board. At the bottom are two tabs used to mount the board to the uBitx board standoffs. The corners of the tabs were removed to make sure there was adequate clearance.

Finally, I added some flexible channel to the shield PCB to make sure nothing would accidentally short out.

Electrical Work - Everything but the uBitx

With the mechanical work completed, it was on to the electrical work. This was mostly making up a number of short connectors as well as soldering up the various bits to interface with the uBitx main board.

This is the start of the wiring up. This picture of the Meduino Mega2650 Pro Mini with the wiring for the TFT display and touchscreen as well as the I2C and power lines for the Si5351 Clock Generator board.

Because of all the additional 5VDC requirements, I added a separate 5VDC supply and distribution buss.

This is a good picture of the TFT touchscreen display. I added the KF2510 connectors to the display as well as the plastic spiral cable wrapping to keep things organized.

Here is the wiring for the power switch, power LED, and the tuning encoder. The cables are not yet wrapped as there is still more to be done.

Here are some pictures of the display running my sketch, as well as the other front panel controls. Unfortunately, I drilled the holes for the power switch and LED without the tuning knob in place. This resulted in the power LED being slightly obscured. Oh well, I guess I could fit a smaller knob.

Electrical Work - The uBitx

With a functioning controller, now come the part where the controller, clock generator, and display must be actually hooked up to the uBitx (instead of the Raduino). In addition, the remaining controls and jacks must be connected.

As I was not using the Raduino to run the sketch and control the oscillator clocks, I needed a was to connect the clock module with the uBitx main board. I used RG_174 coax (I normally tend to use RG-316, but the RG-174 is more flexible) to connect the connect the SMA connectors on the clock module with the Dupont connectors on the uBitx main board. Each cable was about 14 inches long to allow easy separation of the top and bottom of the case while still having all the connections intact.

The connection from the uBitx main board to the antenna BNC connector was also done using RG-174 coax.

Software Work

The software I used for a base for all of my changes was the Arduino TFT + Touchscreen for the uBitx sketch written by VU2SPF and VE1BWV. The best place to start with this software is this UBITX.NET site page.

Because the Adafruit 2050 TFT Touchscreen display is not designed as an Arduino shield, it is necessary to configure the pins used as though it were an Arduino shield. Detailed information about the Adafruit display may be found here.

The modifications to the base code consists of two primary changes:

The data pins. The display D0 and D1 pins connect to the Arduino ATmega2560 digital pins #8 and #9. The display D2 through D7 pins connect to the Arduino ATmega2560 digital pins #2 through #7. NOTE: the pins used on the ATmega2560 correspond to the usual Arduino UNO shields. Not the digital pins #22 through #29 as sometimes seen.
The touchscreen pins. In a lot of the sketches I have seen, the touchscreen pins (Y-, X-, Y+, and X+) are shared with other display pins (#9, C/D, CS and #8). While this is 100% supported, the software engineer in me felt it was unnecessary with all the I/O pins available on the ATmega2560. In my case, using the Meduino Mega2650 Pro Mini, using separate pins made the cabling easier.
As the Adafruit display is a 480x320 display, some of the positions of the text in the display will require some adjustment. (I have not done this yet.)

In the process of implementing support for the Adafruit 2050 display, a bug was discovered in the MCUFriend TFT support (used by the VU2SPF/VE1BWV sketch) for the H8357D display controller. This bug manifested itself as having all the colors in the display inverted. It is worth mentioning the work around is very simple. The MCUFriend owner/developer is aware of this bug.

I hope you have enjoyed hearing about this project. It was a fairly straight forward, and easy, project. I'm sure it will be lots of fun to operate, until I decide on the next enhancement. VBG

Mark, N1VQW

May 1, 2018

Here is an example of the layout technique I used for making all the necessary holes in the project box. I covered the panel with (easy to remove) masking tape and then used a pen to mark the locations.
Here is the completed front panel with all the necessary holes drilled and the opening cut for the display. From left to right, the opening / holes are for A large rectangular opening for the TFT display. Holes for the key, microphone, and headphones. (I haven't yet settled on the order.) A hole for the volume control. A hole for the tuning encoder. Holes for the power LED (top) and power toggle switch (bottom).
Here is the completed rear panel with all the necessary holes drilled. From left to right, the holes are for A hole for the BNC antenna connector. A hole for the PA fuse. A hole for the main board, display, Mega2560, and Si5351 boards. A hole for the power connector. A small hole for a mini-USB connector.
Here are pictures of the Mega2650 and Si5351 boards mounted to the top of the cabinet, the rear panel with all the hardware mounted, and the front panel with all the hardware mounted.
Here is the uBitx main board mounted to the bottom of the cabinet. While not shown in the above pictures, the front and rear panels had to be notched to allow room for the standoffs used to mount the uBitx board.
Here is the picture showing the uBitx board mounted and the front and read panels mounted. This will give you an idea of the layout.
Because there are a number of new boards requiring 5VDC power, I decided to not only add a bit of internal shielding but add a separate 5VDC voltage regulator and distribution buss. I used a two row header with plus on one side and minus on the other. This is very convenient for using two pin headers to the various new boards.
Here is the picture showing the side of the shield facing the uBitx board. At the bottom are two tabs used to mount the board to the uBitx board standoffs. The corners of the tabs were removed to make sure there was adequate clearance.
Finally, I added some flexible channel to the shield PCB to make sure nothing would accidentally short out.

This is the start of the wiring up. This picture of the Meduino Mega2650 Pro Mini with the wiring for the TFT display and touchscreen as well as the I2C and power lines for the Si5351 Clock Generator board.
Because of all the additional 5VDC requirements, I added a separate 5VDC supply and distribution buss.
This is a good picture of the TFT touchscreen display. I added the KF2510 connectors to the display as well as the plastic spiral cable wrapping to keep things organized.
Here is the wiring for the power switch, power LED, and the tuning encoder. The cables are not yet wrapped as there is still more to be done.
Here are some pictures of the display running my sketch, as well as the other front panel controls. Unfortunately, I drilled the holes for the power switch and LED without the tuning knob in place. This resulted in the power LED being slightly obscured. Oh well, I guess I could fit a smaller knob.