Building the Minima An Arduino based HF Transceiver

Thomas - KK6AHT Pacificon 2014

Licensed in 2012 at Pacificon Extra license with K6BJ classes in Dec 2012

Farhan aka VU2ESE

Author of the BITX20

The Minima

Announced on January 16th 2014

General coverage HF Receiver 0 to 30 Mhz

CW and SSB operation

Power output 5 watts (w/ amplifier)

LCD Display - Arduino controlled

Open Source Code

RIT and two VFOs

Super Heterodyne with IF at 20 Mhz

Cost under $100

Arduino - LCD Display Si570 XO (VFO+20Mhz) KISS Mixer

Crystal Filter 20 Mhz

RX Pre-amp

BFO 20 Mhz

Diode Mixer

AF Pre-amp

AF Amp

34.285

CQ CQ … 20 Mhz

CQ CQ … 14.285

CQ CQ … 20 Mhz

CQ CQ …

Ardu

ino

- LC

D

Dis

play

Si

570

XO (V

FO+2

0Mhz

)

KISS Mixer

Crystal Filter 20 Mhz

RX Pre-amp

BFO 20 Mhz Diode

Mixer

AF Pre-amp AF

Amp

Arduino - LCD Display Si570 XO (VFO+20Mhz) KISS Mixer

Crystal Filter 20 Mhz

TX Pre-amp

BFO 20 Mhz

Diode Mixer Mic Amp

34.285

CQ CQ … 20 Mhz

CQ CQ … 14.285

CQ CQ … 20 Mhz

CQ CQ …

LPFs

Ardu

ino

- LC

D

Dis

play

Si

570

XO (V

FO+2

0Mhz

)

KISS Mixer

Crystal Filter 20 Mhz

RX Pre-amp

BFO 20 Mhz Diode

Mixer

AF Pre-amp AF

Amp

Mic Amp

LPFs

TX Pre-amp

CW Tone

TX / RX

Serial Port

Homebrewing the Minima

Measuring the crystal filter

Measuring the crystal filter

• Converting Voltage into Power?

• Impedance of my signal generator?

• Impedance conversion?

• Termination?

Measuring the crystal filter

Reminds me of the roman army in the Asterix and the Roman Agent.!- f

Toroids …

• Do not be afraid

• Get a LCR meter (AADE - $100)

• Watch YouTube videos

• Get multi color magnetic wires for transformers

Home made Arduino

Home made Arduino

• Get a Atmega328P with an Arduino bootloader

• Or better, burn the bootloader yourself

• Enjoy the binary (works / does not work) aspects of the controller board ;)

• If you are not familiar with Arduino, stick to the standard setup for now

Ardu

ino

- LC

D

Dis

play

Si

570

XO (V

FO+2

0Mhz

)

KISS Mixer

Crystal Filter 20 Mhz

RX Pre-amp

BFO 20 Mhz Diode

Mixer

AF Pre-amp AF

Amp

Receiving signals

• It is a lot easier than you think!

• Learnt how to debug amplifiers via transistor biases, temperature and AC-coupled measurements

• Built my first VXO and generating sine waves at 20 Mhz

Finishing up

• Mixer fun: Carrier Suppression, Conversion Loss and IIP3

• Output power, Harmonics and the FCC

• From 50mV to 50V

Lessons learnt

Blocks

• Learnt to see a circuit as blocks and stages

• Everything can be tested and measured independently

• Build, Test, Move on - Each stage is a project

• Keep a notebook - Take lots of notes

Tools• DVM, Scope

• Soldering Iron, MePads, Glue

• LCR Meter

• Some sort of signal generator

• BNC Connectors, 50 Ohm termination, Cables, etc

• Spectrum Analyzer or PHSNA is nice to have

Reference• Minima Initial Article

http://www.phonestack.com/farhan/minima.html

• Minima Mailing List

• And all the Minimas that have been built!

• Experimental Methods in RF Design (EMRFD)

• ARRL Handbook

• Chat With The Designer Podcast (cwtd.org)

Solder Smoke

Bill Meara - N2CQR Book Blog Podcast!!http://soldersmoke.blogspot.com

Closing Remarks

Project Status• Still actively being developed and designed

• The KISS Mixer will probably be replaced by another mixer in the future

• This should not stop you! !

• A few PCBs were made but distribution is limited until the design is finalized !

• You will need the RF386 Power Amplifier (or similar)

Open Source Software• Many contributions to the Minima software

https://github.com/afarhan/radiono

• WA0UWH leading the charge with WSPR support, CW ID, Rotary encoder, etc https://github.com/wa0uwh/radiono_erb

Join the club!Already 4 known Minimas in the bay area.

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Questions? Demo!!

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!Thomas - KK6AHT http://sarfata.org/ham/minima @sarfata

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