4 Band CW QRP Transceiver by DL6ZB
Here's a weekend project for the homemaker.
An Analog Devices AD9850 DDS module from the Internet is the heart of
this tiny multibander. These DDS modules are usually available for less
than 15 US$ / € at Ali, Amazon or ebay.
The AF of the DC receiver is basically a pair of NPN BJTs, a JFET and a
single TL084 quad op-amp. I would say that this is the minimum of
semiconductor components to make a well working shortwave amateur radio
The front-end mixer is a 74HC4066 CMOS switch. This mixer is so good
that almost no additional filters are needed before the mixer. I added
a 3 MHz high pass filter as a precaution to keep strong noise below the
filter's cutoff frequency away from the receiver input. In addition, I
used a widely available microprocessor and a widely available 0.96"
OLED display of type SSD1306 with a size of 128x64 px.
So no components that are difficult to get. Most of it might be found in the junk box of a ham homemaker.
+ AD9850 DDS generator module
+ Microchip ATMEGA328P-PU, 16/20 MHz
+ Rotary encoder for frequency and menu
+ 9k6 RS232 Remote Control, Kenwood system
+ QSK with frequency shift and RX mute
+ Microcontroller sidetone generator
+ Automatic CQ call, also with CQ loop
+ Setup of your individual callsign
+ CW Filter fix for 700 Hz center frequency
+ Contest mode
+ Receiver RIT for split mode operation
+ Relative signal strengh display
+ Battery voltage display
+ I2C OLED display 128x64
+ smooth working IAMBIC keyer WpM 5 to 50
+ Single lever, straight key option
+ Bug key simulation option
+ Output power 5 Watts, MOSFET
+ Elliptic LPF, 80&60 plus 40&30 mtr band
RF LOWPASS FILTERS:
These filters have an
input and output impedance of 50 ohms. I recommend Cauer elliptic
filters for sufficient harmonic suppression.
On the photos you can see
that I do not use cores with the identification color red (T-50-2). Of
course you can do it that way. T37 cores should just work without
heating up too much. However, there is still some room for
experimentation here. Please email me if you have any suggestions for
improvement. The table shown here is just an example.
AF BANDPASS FILTER:
like it when the CW signal I'm interested in is boosted, but the
environment around the frequency still remains audible. Not everyone
likes that. Some like a sharp filter that filters out only the signal
of interest. This example of a DC receiver offers a lot of room for
your own solutions. On the Internet there are a lot of suggestions for
narrowband AF filters that are suitable for use in this receiver. I
took a picture of the actual frequency response from the band noise
from the antenna using SDR software. Note: You can neglect the dB
scaling of the ordinate, because it is only relative.
The transceiver has 2 push buttons: <ENC> and <WpM>.
<ENC> is the rotary encoder's push button.
<WpM> is the multi-function WpM button
|TX ZERO BEAT
|CW SPEED / WORDS PER MINUTE
|<ENC> + <WpM>
Auto CQ Loop, 10 times CQ, spacing 10 seconds
Auto CQ loop, 10 x, spacing 2 seconds
Table of functions for both push buttons on the front panel.
AUTO CQ may be interrupted by pressing either push button <WpM> or <ENC>.
Without valid callsign AUTO CQ is disabled.
PC REMOTE CONTROL:
The transceiver partially
emulates the Kenwood TS-480 PC remote control. The RS232 speed is 9600
baud, 8N1. I have tested the remote control with several PC ham radio
software like CQRLOG, DXLab and others. However, I haven't implemented
every KENWOOD command, so I can't guarantee that it works with every
available PC software.
Click here for download: FIRMWARE ZIP FILE
Clock speed is set to 20 MHz.
Latest: MARCH 31, 2023 V 1.0.12
Please send me an e-mail if you have any questions about the project. firstname.lastname@example.org
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The software for DL6ZB's ZB-4 CW QRP Transceiver is freeware in the best sense of "Ham Spirit" with
the following restrictions. You may download and use the software for
your projects and copy and distribute the download link as you want.
You may redistribute the software, but you may not modify the software
without my permission. You may not modify the copyright notice.
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