Circuit6040 - Home Page - N3FJZ

Updated: 12-22-2020

Visit my ZX-SSB-II Homebrew Project:

Schematics - YouTube Videos - Firmware (Arduino Sketch)
Note: The ZX-SSB-II is still a work in progress...

The ZX-SSB-II HF SSB transceiver project IS NOT a kit, nor is it an exhaustive step-by-step guide for the first-time radio builder; it's simply a documented accounting of my latest homebrew Amateur radio rig that performs reasonably well for my needs at this time, with schematics, component layouts and Arduino sketch (source code). I'm presenting it here as my way to "give back" to the Amateur radio community in some small way and to contribute in the advancement of the radio art. I make no claims that the ZX-SSB-II design upholds the best practices in RF design, I simply studied, adapted and recreated selected circuit ideas from the works of many of the well known homebrew Radio Artisans that have presented their endeavors to the world. My criteria in the selection of circuits included in the design were to keep the building blocks as basic as possible, but still be able to provide reasonable performance using low cost components available today. I used an Arduino microcontroller as the user interface and an Si5351 PLL oscillator for the VFO and BFO for frequency stability and accuracy.

Its features include:


What's new:
2020-11-06 - A new build (#20201106) of the Arduino Sketch (source code) is available. This new build makes changes to the Tune GUI page as follows:
- SWR measurement now fully functional.
- Improved Forward and Reflected power measurement method allows bar-meters to be linear.
- Numeric indicators for Forward power, Reflected power, and SWR added.
- Temperature sensor code and temporary temperature readouts added to Home GUI page for development. These rudimentary temperature sensors use low cost switching diodes as the mesurement elements and only have a resolution of 2.2c (4f) degree per count but will provide sufficient resolution to support the high temperature shut-down protection to the PA final transistors.

2020-09-05 - A new video (Part 16) shows the improvements to the Tune GUI screen's SWR, Forward and Reflected bar-meters along with the circuit changes necessary to the RF detector module and Front Panel to support those improvements.

2020-09-05 - Circuit changes to the RF Power detector circuit. The changes are as follows: Remove the calibration potentiometers in the RF detector module so that the output of the Stockton bridge goes directly to the front panel

2020-09-05 - Circuit changes to the Front Panel. The changes are as follows: Replace the zener diodes on PWR_FWD (A5) and PWR_REV (A6) (to ground) with 470k resistors. Replace the series 1k resistors on PWR_FWD (A5) and PWR_REV (A6) with 220k resistors.

Older Updates:
• 2020-08-20 - A new build (#20200820) of the Arduino Sketch (source code) is available. This new build reads the analog outputs from the Stockton bridge and makes the Forward Power and Reflected Power bar-meters on the Tune GUI screen functional. This update is in preparation for the final bit of work which will more precisely calibrate the bar-meters themselves, and finally make the SWR bar-meter functional using calculations fed by the forward and reflected power values.

2020-08-20 - A new video (Part 15) shows the Tune GUI screen and initial tests conducted on the Forward and Reflected bar-meters.

• 2020-07-19 - Added S-Meter detector circuit.

• 2020-07-12 - A new build (#20200712) of the Arduino Sketch (source code) is available. This new build implements a "Tune" GUI screen with SWR, Forward Power, and Reverse Power bar meters. While on this screen, a control line will unbalance the balanced modulator so that when the PTT is pressed, the PA will produce a CW RF output signal allowing the adjustment of an antenna match while monitoring SWR, Forward and Reverse RF output power; however, while the bar meters are indeed present the screen, they are only static at the moment; i.e. logic has not yet been completed to couple the bar meters to the analog inputs of the Arduino.

• 2020-07-12 - A new build (#20200712) of the Arduino Sketch (source code) is available. This new build implements a "Tune" GUI screen with SWR, Forward Power, and Reverse Power bar meters. While on this screen, a control line will unbalance the balanced modulator so that when the PTT is pressed, the PA will produce a CW RF output signal allowing the adjustment of an antenna match while monitoring SWR, Forward and Reverse RF output power; however, while the bar meters are indeed present the screen, they are only static at the moment; i.e. logic has not yet been completed to couple the bar meters to the analog inputs of the Arduino.

• 2020-06-22 - A new video (Part 12) shows how to change the default baudrate in the Ublox NEO-6M GPS module using Ublox's U-Center.

• 2020-06-26 - Several wiring additions have been made to the ZX-Front-Panel schematic to support the inclusion of PTT (Push To Talk) control via the Arduino controller. If you've built the ZX-Front-Panel from an earlier schematic (prior to 6-26-2020), you'll need to make the following wiring additions to be able to use the new PTT control functionality in firmware releases dated 6-26-2020 (20200626) and later:

- Add a connection from an external N.O. (normally open) momentary switch and capacitor to pin 38 of the Arduino to ground. This is the connection from the PTT switch, typically on the microphone, that when grounded (pressed) indicates that the operator wishes to Transmit.

- As shown in the ZX-Front-Panel schematic, add a 2N3904 (or any general purpose NPN switching transistor), two resistors, and a capacitor between the Arduino pin 39 and the rig's /PTT (active low) control circuit. The /PTT (active low) line typically controls the PTT relay or other power control mechanism that, when low, switches the RF circuits from Receive to Transmit.

By passing the PTT request through the Arduino, features such as shutting down the transmitter when the final transistors get too hot or when there's a high VSWR, limiting the time the transmitter is on, preventing transmissions outside the Amateur band, putting the transmitter into 'Tune' mode, and implementing a station I.D. reminder timer, et cetera, will be possible.

• 2020-06-26 - A new build (#20200626) of the Arduino Sketch (source code) is available. This new build implements the PTT (Push To Talk) control via the Arduino controller as described above.

• 2020-06-23 - A new build (#20200623) of the Arduino Sketch (source code) is available. This new build includes the real-time display of the 10 MHz reference on the crystal trim screen on both the color and monochrome displays. This allows the operator to trim the Si5351 master crystal oscillator while monitoring the 10 MHz reference error.

• 2020-06-21 - A new video (Part 11) showing the features of the new sketch build (#20200621).

• 2020-06-21 - A new build (#20200621) of the Arduino Sketch (source code) is available. This new build includes a GPS disciplined RF frequency counter that uses the Ublox NEO-6M GPS module's 1-PPS signal as its gate.

• 2020-06-19 - Made several wiring changes to the ZX-Front-Panel schematic in preparation for the inclusion of the frequency counter, a second rotary encoder, and assignment of pins for future functionality. If you've built the ZX-Front-Panel from the earlier schematic (prior to 6-19-2020), you'll need to make the following wiring changes to be able to run any firmware releases dated 6-19-2020 (20200619) or later:
- Move S-Meter input from A10 to A7 (currently this is the potentiometer used during development)
- Move the LED for General Class TX Privilege from 22 to 45
- Move the LED for Extra Class TX Privilege from 23 to 44
- Add the 74LV8154 chip and associated connections to the Mega 2560
- Add a connection from the GPS module's 1-PPS output to pin 7 of the 74LV8154 and to pin A11 of the Mega 2560
- Add the second rotary encoder and associated connections to the Mega 2560

• 2020-06-14 - A new build (#20200614) of the Arduino Sketch (source code) is available. This new build includes indicators showing the license class that has TX privilege for the dial frequency.

• 2020-06-13 - A new video (Part 10) showing the GPS clock on the monochrome display.

• 2020-06-11 - A new build (#20200611) of the Arduino Sketch (source code) is available. This new build includes the ability to adjust the Si5351's output level real-time from the user interface and other improvements.

• 2020-06-11 - A new video (Part 9) showing the new features.

• 2020-06-05 - New Arduino Sketch (source code) and schematic for the new ZX-Front-Panel with color display and GPS linked clock.

The navigation bar on the left contains the following sections:

-Projects-
This section contains links to actual construction projects that contain full documentation and source code from which you can reproduce the project. If the notation "(Still in Development)" appears, the project documentation is not yet complete and subject to revision as I refine each module.

-Reference-
This section contains links to other projects I've built, but are being presented as-is for reference only with no plans to develop the documentation beyond what's currently presented.

-Links-
This section contains links to other websites that I've found to be a valuable resource.


Disclaimer:
SOME OF THE ARTICLES CONTAINED HEREIN DESCRIBE THE BUILDING OF RADIO TRANSMITTING AND RECEIVING DEVICES WHICH REQUIRE THE BUILDER TO HOLD A VALID USA FCC AMATEUR RADIO LICENSE (OR OTHER GOVERNMET ISSUED LICENSE FOR THE COUNTRY OR LOCATION IN WHICH THE BUILDER RESIDES), WHICH MAY NOT BE CLEARLY IDENTIFIED AS REQUIRING SUCH LICENSE, TO BE ABLE TO ACTUALLY CONSTRUCT AND USE SAID DEVICES TO RECEIVE AND OR TRANSMIT ON THE AIR USING FREQUENCIES AUTHORIZED BY SUCH LICENSE. IT IS THE RESPONSIBILITY OF THE INDIVIDUAL READER TO VERIFY THE LEGALITY OF ANY ACTIONS DESCRIBED IN THESE FILES.

ALL INFORMATION, INSTRUCTION AND OR COMPUTER SOFTWARE CONTAINED WITHIN THIS WEBSITE IS BEING PROVIDED 'AS IS' AND WITHOUT WARRANTY OF ANY KIND, EITHER EXPRESSED OR IMPLIED. THE ENTIRE RISK AS TO THE SUITABILITY, QUALITY, SAFETY, AND PERFORMANCE OF THE INFORMATION, INSTRUCTION AND OR COMPUTER SOFTWARE IS BORNE BY THE USER. SHOULD THE INFORMATION, INSTRUCTION AND OR COMPUTER SOFTWARE PROVE DEFECTIVE IN ANY RESPECT, THE USER WILL ASSUME THE ENTIRE COST OF ANY SERVICE AND REPAIR AND WILL ASSUME FULL LIABILITY FOR ANY INDIRECT, SPECIAL, INCIDENTAL OR CONSEQUENTIAL DAMAGES ARISING OUT OF THE USE OF OR INABILITY TO USE THE INFORMATION, INSTRUCTION AND OR COMPUTER SOFTWARE, INCLUDING, WITHOUT LIMITATION, DAMAGES FOR LOSS OF GOODWILL, WORK STOPPAGE, COMPUTER FAILURE OR MALFUNCTION, OR ANY AND ALL OTHER PERSONAL DAMAGES, INJURY OR LOSSES, EVEN IF ADVISED OF THE POSSIBILITY THEREOF, AND REGARDLESS OF THE LEGAL OR EQUITABLE THEORY (CONTRACT, TORT OR OTHERWISE) UPON WHICH THE CLAIM IS BASED.