Posts Tagged ‘buildathon’
CW decoder – The electronics
July 30th, 2015 | 
Author: I found a circuit online that refers to a QST article in 1999, that shows a CW zero beat decoder. It uses a LM567 that converts the audio signal and switches on a LED to show the operator has achieved a zero beat. The project has a variable resistor that can be used to tune or “swing” the centre frequency – This was a good start for me, and I created the following schematic for the build and set to work constructing it on the breadboard.
As you can see its very simple indeed. I did differ from the published design and found that I could use a single .22uF capacitor across the output pins. So here is a breakdown of the build :
C1 0.1µF
C2 0.1µF
C3 1µF
C4 0.22µF
C5 0.47µF
VR1 10kΩ
R2 470Ω
IC1 LM567
LED1
Arduino Uno – Rev 3 (or any suitable Arduino copy etc)
20x4 LCD display ( Im using a I2C display. This takes up less wiring to achieve the same result)
Once I had built the electronics, and before I tested it on the Arduino it was time to feed the circuit with some audio. Luckily I have a audio output from the FT-2000 which had enough volume to trigger the IC.
After some adjustments on the potentiometer the LED was flashing in time with the tones being received on the 20m band at 750Hz audio frequency, This was great, with no mistakes and on the 1stattempt the circuit burst into life. here is the breadboard layout of the 1st attempt. It is laid out subtly different - for ease of understanding only. (also be aware I'm using an I2C display - and in this version I was using a 2 line display)
CW decoder – The electronics
I found a circuit online that refers to a QST article in 1999, that shows a CW zero beat decoder. It uses a LM567 that converts the audio signal and switches on a LED to show the operator has achieved a zero beat. The project has a variable resistor that can be used to tune or “swing” the centre frequency – This was a good start for me, and I created the following schematic for the build and set to work constructing it on the breadboard.
As you can see its very simple indeed. I did differ from the published design and found that I could use a single .22uF capacitor across the output pins. So here is a breakdown of the build :
C1 0.1µF
C2 0.1µF
C3 1µF
C4 0.22µF
C5 0.47µF
VR1 10kΩ
R2 470Ω
IC1 LM567
LED1
Arduino Uno – Rev 3 (or any suitable Arduino copy etc)
20x4 LCD display ( Im using a I2C display. This takes up less wiring to achieve the same result)
Once I had built the electronics, and before I tested it on the Arduino it was time to feed the circuit with some audio. Luckily I have a audio output from the FT-2000 which had enough volume to trigger the IC.
After some adjustments on the potentiometer the LED was flashing in time with the tones being received on the 20m band at 750Hz audio frequency, This was great, with no mistakes and on the 1stattempt the circuit burst into life. here is the breadboard layout of the 1st attempt. It is laid out subtly different - for ease of understanding only. (also be aware I'm using an I2C display - and in this version I was using a 2 line display)
CW decoder – Introduction
If you do follow me on twitter (and if you don’t – you really should) you will have no doubt seen my recent tweets about constructing a CW decoder. After a number of retweets, and favorites from other very interested hams – I did promise that I would collate all my knowledge into a blog posts and share the details with you all.So, for those who have not been following me on twitter – here is the sales pitch. I recently started looking at some projects that I could get my Arduino Uno involved in with the radio hobby. I have a number of reasons why I want to combine radio, Arduino and some electronics – more about this later.
I stumbled across a video on YouTube where Budd Churchward showed his Arduino copying and decoding CW straight off the HF band and at a reasonably high speed. I ventured further and wanted to know what electronics Budd was using to achieve this excellent little project.
I used the limited shared knowledge and discovered that the electronics is basally a LM567 – Tone decoder chip that (I have since discovered the chip is used in the ARRL book for Arduino Projects) I discovered takes an audio input and converts this to a HIGH / LOW output suitable for the Arduino to use as a signal for decoding.
Finding a suitable project for the LM567 and trying to work out how fellow constructors had configured their LM567s was not an easy task. This did indeed take quite a lot of chasing and head scratching. I will go into more technical detail on the next post – but for the reason why I wanted to complete this ? very simple. I w
ant to create a project that would “inspire” young electronically minded students that might have an interest in radio – (i.e the morse code) some coding experience and some construction / electronic interest. This project covers all 3 areas, and only lightly covers each subject area.
In the next post – I show the LM567, the schematic and give you the list of parts required.
CW decoder – Introduction
If you do follow me on twitter (and if you don’t – you really should) you will have no doubt seen my recent tweets about constructing a CW decoder. After a number of retweets, and favorites from other very interested hams – I did promise that I would collate all my knowledge into a blog posts and share the details with you all.So, for those who have not been following me on twitter – here is the sales pitch. I recently started looking at some projects that I could get my Arduino Uno involved in with the radio hobby. I have a number of reasons why I want to combine radio, Arduino and some electronics – more about this later.
I stumbled across a video on YouTube where Budd Churchward showed his Arduino copying and decoding CW straight off the HF band and at a reasonably high speed. I ventured further and wanted to know what electronics Budd was using to achieve this excellent little project.
I used the limited shared knowledge and discovered that the electronics is basally a LM567 – Tone decoder chip that (I have since discovered the chip is used in the ARRL book for Arduino Projects) I discovered takes an audio input and converts this to a HIGH / LOW output suitable for the Arduino to use as a signal for decoding.
Finding a suitable project for the LM567 and trying to work out how fellow constructors had configured their LM567s was not an easy task. This did indeed take quite a lot of chasing and head scratching. I will go into more technical detail on the next post – but for the reason why I wanted to complete this ? very simple. I w
ant to create a project that would “inspire” young electronically minded students that might have an interest in radio – (i.e the morse code) some coding experience and some construction / electronic interest. This project covers all 3 areas, and only lightly covers each subject area.
In the next post – I show the LM567, the schematic and give you the list of parts required.
Intermediate is go
In class students are also welcomed to join the distance learning students so missing a lesson is no longer such an issue.
Over the coming weeks I will be creating some companion videos showcasing the practical elements of our in lesson activities.
So far we have 5 in class and around 30 distance learning joining us for the next 10 weeks.
Foxx 3 TRX build
So it was my birthday recently and to celebrate the turning of another year and that I had indeed taken a day off – I decided to build a FOXX 3 QRP CW transceiver. These little kits are available from Kanga-products.co.uk and are designed to fit in a Altoids tin.The kit comes pre bagged up in separate bags, and its just a case of soldering the correct component to the correct area on the circuit board. The kit itself is a 1 Watt QRP transceiver that can be bought on various bands. Mine was for the 20m band.
The board has a clear and easy to read Silkscreen and the pads are suitably wide enough to allow anyone with different levels of skill to create the kit. Each step allows you to test each part of the board, so you learn how each part of the kit relates to the transceiver as a whole.
I had a great time building it, it’s a simple, easy and great fun little kit. I hope to take it out and about – so hopefully you can hear my tiny signal on 20m soon.
