assembly of sandwich digital vfo mod ii · 1 – 3 mm dual color led 1 – 27 mhz crystal 5 – 1 k...

1

Assembly of Sandwich Digital VFO MOD II 26 August 2020

Original Sandwich Module Sandwich II (or 2)

Contents Part List ................................................................................................................. 2

Product Overview: ................................................................................................ 3

Assembly Overview: .............................................................................................. 5

Header Pin Assembly: ........................................................................................ 5

Assembly Begin: ................................................................................................. 8

Function Description: .......................................................................................... 11

In normal mode ................................................................................................ 11

Calibration ........................................................................................................ 11

Modification Possibilities .................................................................................... 13

With this new PCB ............................................................................................ 13

2

Part List 9 – 104 capacitors 1 – Rotary encoder with switch 1 – 3 mm dual color LED 1 – 27 MHz crystal 5 – 1 k resistors 3 – 330-ohm resistor 1 – PCB – Main PCB with the si5351a pre-mounted 1 – PCB - 3.3V/8MHz Arduino pro mini compatible PCB – preprogrammed. 2 – 4 pin 2.54 mm pin headers (may be in package for you to separate) 3 – 2 pin 2.54 mm pin headers. 1 – 2 pin yellow header is used for the I2C bus for additional capability. 1 – 6 pin right-angle header for programming the Arduino – optional. 2 – single right-angle header pins for 8VDC and GND connection.

Arduino Mini – 3.3 v core.

RAW: 5.5v to 12 vdc.

Product may vary slightly

3

Product Overview: Sandwich II is a Digital VFO which is electrically equivalent to the original

Sandwich model produced by CRKITS.com. The original is no longer available.

The new board contains all the components contained on the original Control and

OSC boards. The same Arduino attaches to the back of the new PCB instead of

being between the Control and OSC boards.

The new board will plug into the space vacated by the TUNE control on the

original KN-Q7A for ground and 8vdc connections. Present models, KN-Q7A, CS

Series SSB Transceivers produced by CRKITS.com are compatible with this module

as they were with the original Sandwich. The yellow header pin extends the I2C

connection capability for additional add-on options such as a digital frequency

display (Arduino program must be modified).

By adding the Sandwich, you can have full band coverage with LED frequency display. The frequency stability is the same as a crystal with little thermal drift even when you transmit all the time. Unlike a DDS, the Sandwich digital VFO will not bring lots of birdies. It supports BFO calibration so both USB and LSB modes are supported. It also supports crystal frequency calibration so you will be exactly at the kHz or 100 Hz. JP10 = Jumper to select band high limit, BFO and default operation frequencies. Start up frequency is determined by the Arduino Software. Band Hi limit and Band Low limit are also determined by the Arduino Software. USB/LSB limits are also determined by the Arduino Software.

4

Calibration values are stored in the internal memory of the Si5351a chip. Values for the USB or LSB can also be stored in the internal memory of the Si5351a chip so that on power up, the start up frequency and setting of the USB/LSB will be the same as prior to shut down.

Frequency Examples:

80 Meters

a) High Frequency: 4.0000 MHz

b) Low Frequency: 3.5000 MHz

c) Start Frequency: 3.8000 MHz

d) BFO: IF Frequency +/- 4 KHz

40 Meters





20 Meters





15 Meters





Frequency can be adjusted for your region in the Arduino software.

5

Assembly Overview: DO NOT ASSEMBLE YET

Note: The main board is dual sided. Assemble the resistors and capacitors first. Follow by the header pins and then the Rotary encoder last.

Back Front

Header Pin Assembly: For ease of assembly header pins are assembled as a 4 in line header pin or a dual

in line header pin as follows:

A. JP1 and JP3 use a 4-header pin connector black.

B. JP4 and JP6 use a 4-header pin connector black.

C. JP2 is a yellow dual header pin

D. JP5 is a dual pin black

E. JP10 is a dual pin black

F. JP11 is a dual pin black

Note: JP5 may be labeled as JP9 on PCB

JP1 location is to be inserted on the Back and soldered on the Front for

connection to the Arduino pin D2 and GND.

JP2 location, yellow header pin is to be inserted on the Back and soldered on the

Front for connection to the Arduino pin A4 and A5 (I2C bus). Short side is

soldered while the long side will extend through the Arduino.

6


connection to the Arduino pin D4 and D3.


connection to the Arduino pin VCC and RST (RST pin is not used) (VCC pin is for

3.3VDC to Si5351a chip. JP4 is not used if the Arduino is a 5vdc core.


connection to the Arduino pin D10 and D11.


connection to the Arduino pin RAW and GND. (RAW pin is 8VDC from main Radio

board).

JP10 location can be soldered on the front or back. It can be a jumper wire or left

open. An option would be to put a header pin with a shorting jumper if you

wanted to use this connection as a programming option.


connection to the Arduino pin D7 and D6 (D6 is not used)

LSP1 – GND connection to radio PCB

LSP2 – 8VDC connection to radio PCB

Component Location (Front or Back)

FRONT

1) Rotary encoder with switch 2) Dual-color LED

3) Capacitors:

a. C1 – 0.1 uf

b. C2 – 0.1 uf

c. C3 – 0.1 uf

4) Resistor R3 (1K ohm)

5) JP10 Optional Front of Back

BACK

1) X2 – 27 MHz crystal

7

2) IC1 – Si5351a chip (pre-soldered)

3) J1 – 3.3 VDC regulator (not used, not included)

4) Capacitors:

a. C4 – 0.1 uf

b. C5 – 0.1 uf

c. C6 – 0.1 uf

d. C7 – 0.1 uf

e. C8 – 0.1 uf

f. C9 – 0.1 uf

5) Resistors:

a. R1 – 1K ohms

b. R4 – 1K ohms

c. R5 – 1K ohms

d. R6 – 1K ohms

e. R7 – 330 ohms

f. R8 – 330 ohms

g. R9 – 330 ohms

6) Header Pins

a. JP1 & JP3 (black)

b. JP4 & JP6 (black)

c. JP2 (yellow)

d. JP5 (black)

e. JP10 (optional front or back)

f. JP11

8

Assembly Begin: Capacitors and Resistors

Insert C1, C2 and C3 on the Front side of the PCB.

Solder three capacitors on the Back side of the PCB and clip wires

Insert R3 on the Front side of the PCB

Solder R3 on the Back side of the PCB and clip wires.

Insert C4, C5, C6, C7, C8, C9 on the Back side of the PCB

Solder six capacitors on the Front side of the PCB and clip wires.

Insert R1, R4, R5 and R6 on the Back side of the PCB

Solder four resistors on the Front side of the PCB and clip wires.

Insert X2 (27 MHz crystal) in location on Back side of PCB

Solder X2 on Front side of PCB and clip wires

Note: R8 will fit tight if inserted and soldered prior to installing X2.

Insert R7, R8 and R9 on the Back side of the PCB

Solder three resistors on the Front side of the PCB and clip wires.

Other components

Alignment might be easier if the pins are inserted in the Arduino for alignment

with the PCB. Do Not solder the wires on the Arduino at this time. Remove the

Arduino after the header pins have been soldered to the Front of the PCB.

Insert the JP1&JP3 header pins from the Back side of the PCB.

Solder JP1&JP3 from the Front, clip, and trim wire on the Front side.

Insert the JP4&JP6 header pins from the Back side of the PCB.

Solder JP4&JP6 from the Front, clip, and trim wire on the Front side.

Insert the JP5 header pins from the Back side of the PCB.

Solder JP5 on the Front side of the PCB, clip, and trim wire on the Front

side.



side.

Insert the JP2 header pins (yellow) from the Back side of the PCB.

9


side.

Remove the Arduino for later installation.



side.

Insert dual color LED on Front side of PCB and adjust height to about (0.2

inches or 5.10 mm) from the PCB to the bottom of the LED.

Solder dual color LED to Back side of PCB and clip wires.

Insert Rotary encoder with switch on Front side of PCB

Solder Rotary encoder on Back side of PCB and clip and trim wires.

Insert a single right-angle header pin (LSP1) on Front of PCB

Solder LSP1 on Back side of PCB clip and trim wire, remove BLACK plastic

section.

Insert a single right-angle header pin (LSP2) on Front of PCB

Solder LSP2 on Back side of PCB clip and trim wire, remove BLACK plastic

section.

Final Assembly

Align the preprogrammed Arduino with the Back side of the Sandwich PCB.

Component side of the Arduino should be facing the Sandwich PCB.

Do not press the Arduino tight to the base of the header pins. The Reset

button and other components need to be above the Back PCB components.

Solder the pins on the back side of the Arduino.

DO NOT Trim the yellow header pins. This is the I2C external connection.

Trim the other header pins.

Connections to CLK0, CLK1 and CLK2 will not be done at

this time.

Prepare the SSB Radio for insertion of the Sandwich Module

Insert the LSP1 and LSP2 pins in the TUNE block of the PCB on the radio.

The edge of the PCB should be flush with the radio PCB at a right angle.

10

Solder pins and trim.

Connect the CLK0 pin to the appropriate spot on the SSB Radio PCB. The

CLK0 is the Oscillator control. Radio Frequency = CLK0 - IF frequency.

Connect the CLK2 pin to the BFO section of the radio.

11

Function Description: Based on original software included with the original Sandwich, the current firmware dated February 26, 2017 supports two modes: Normal mode and Calibration mode. The latter is activated by pressing and holding the encoder button at power on. In calibration mode, pressing the encoder button can toggle between BFO calibration and crystal calibration. At power on, you can easily tell the mode from the color of the LED: red for Normal mode and orange for BFO calibration mode.

In normal mode With power on, pressing the encoder button will toggle between step 1 kHz and 100 Hz, and it is good enough for SSB application. In 1 kHz step mode, LED green means 1, 3, 5, 7, 9 kHz, LED out means 2, 4, 6, 8 kHz, and LED orange means 10, 20, 30, 40, 50, 60, 70, 80, 90 kHz, and LED red means 100 kHz, 200 kHz, and LED red also means out of band. In 100 Hz step mode, every 2, 4, 6, 8 kHz, you can also see green. See the following table to understand it better.

In calibration mode, pressing the encoder button will toggle between BFO calibration and crystal calibration, and meanwhile memorize the last setting to EEPROM. In BFO calibration mode, LED is orange unless it is tuned out of range (red), and the step is 100 Hz. In crystal calibration mode, LED is green, and the step is 20 Hz.

Calibration Press and hold the button on the rotary encoder, then power on the radio. You will see LED is orange meaning it is in BFO calibration mode. Press button again to enter crystal calibration mode, carefully hook a frequency counter to JP8 (CLK1), turn the encoder counter-clockwise for about 70 steps and monitor the frequency counter to as close as 10.000000 MHz, then press the button to memorize the crystal calibration setting. (Setting is stored in memory of Si5351a chip) Remove power supply from radio. Re-enter BFO calibration mode by pressing and holding the button and power on again. Same as KN-Q7A, you will need to

12

download an audio spectrum analyzer software from: http://www.qsl.net/zl1an/Software/Spectrum3.zip. (Personally, I adjust while listening to an SSB audio signal for my liking.) Unzip and double click the spectrum2.exe file to run. Connect the speaker out to the microphone input of the sound card on PC. You will also need to connect a noise generator or simply an antenna to the antenna connector and apply power supply to KN-Q7A radio. Follow the setup on the screen capture below, and click start, you will see a similar audio spectrum. If not, you may need to turn clockwise or counterclockwise the IF GAIN control. In BFO calibration mode, tune encoder to move the passband to the left or to the right. You can use the cursor to read the frequency and level of the signal (on the left bottom corner) to identify the low and high end of the pass-band, so you can get about 350 Hz~2200 Hz range. If you have wider or narrower range, please make sure you still set the lower end of 350 Hz. Please note that, if you are using an antenna to do this, you should tune away from any signal to use the band noise as a random noise source, or the spectrum will jump up and down making the measurement very difficult. Please also note, both LSB and USB will be possible since the BFO calibration range is wider now. If you can see correct audio spectrum range but cannot receive clear voice signal of the intended side band, you might need to tune encoder again to use the correct side band. Normally, the default value should be very close to the intended mode. Just a few steps tuning should be okay. Once it is done, press the button to memorize the setting to EEPROM.

http://www.qsl.net/zl1an/Software/Spectrum3.zip

13

Modification Possibilities Sandwich is a small kit providing the basic feature as a digital VFO. If you know Arduino and electronics quite well, you might want to add a few features by yourself. On the Main board, you can find a few unused pins of Arduino board, including analog pin A3 and digital pin D6 (PWM output possible). You probably need to detect TX or RX status, so you can show different LED colors, or provide TX/RX offset for CW mode. You probably also need to detect SWR, RF power and other analog parameters. Another great idea might be adding an audio Morse Code reporter of the current frequency instead of counting all the time. The fun of a kit is not only building but modifying and sharing. Please share your great ideas to the team at: http://groups.yahoo.com/group/CHINA_QRP/ Also check my website at https://qrvtronics.com/ Arduino software is available upon request from https://qrvtronics.com/

With this new PCB With this new PCB, it is possible to add the Optional Arduino Nano adaptor board. This will allow the use of the Arduino Nano instead of the Arduino Mini. Even though the Arduino Nano costs a few dollars more, it has a built in USB programming connection, more memory, and a faster processor.
http://groups.yahoo.com/group/CHINA_QRP/https://qrvtronics.com/https://qrvtronics.com/

assembly of sandwich digital vfo mod ii · 1 – 3 mm dual color led 1 – 27 mhz crystal 5 – 1 k...

Documents