DL7PK

Contact:
qsl --@-- dl7pk.de

Here Is Your QSL CARD:

enter your call sign (upper case):
        
date of QSO (YYYY-MM-DD) :    

I use eQSL too !!!    www.eQSL.cc

CALLDATEQTRQTHCOUNTRYQRGRST
DD5VL2025-10-3016:27DRESDEN7.19059 /
DL7SL2025-10-3016:267.19059 /

My Shack:


License since 1969

My Homebrewed Transceiver (Vers.2)

This homebrewed QRP-transceiver was designed and built by myself between 2018 and 2021. I use SDR technology for signal processing (2 Raspberry Pies with high-quality USB sound cards) and I also use a number of analog modules. It is designed for amateur bands between 80m and 10m and has an output from 5 Watt to 30 Watt (more with external equipment). (Top View).

Picture in Picture for S-Meter and Spectrum

I use a DDS-Generator from AK-Modul-Bus (0 to 24 MHz) to generate the VFO-Signal. It is controlled by the TX-Raspberry-Pi (1,75 MHz to 15 MHz) and followed by an OPAMP. (Foto).

The RX-Mixer is a small board from China. I added an 8 times frequency-multiplier (from AK-Modul-Bus) to get the max. Frequency of 120 MHz. This signal is devided by 4 using two FlipFlops to get two signals with a Phase difference of 90 degrees (3,5 MHz to 30 MHz). With two of these Mixers I get the IQ-Signals for the Stereo Sound card (24 Bit, Delock 61961 or 63926). In Front of this I use a RF-Amplifier-Board from China.

The following diagram shows the RF-Part of the receiver using a hungarian Filter switched by Diodes and a homemade RF-Amplifier with 3 resonant circuits, tuned by C-Diodes (Diagram).

The Transmitter uses the same Mixers for Modulation. It is followed by a RF-Poweramplifier (Kit) from KN-Electronic (max. 50 W) and a Lowpass-Filter (Kit from KN-Electronic).

My Transceiver Software:

The Raspberry-Pies are running under DEBIAN Linux. I use the Module "GNU-Radio" to generate the Top-Classes of my PYTHON-Programs. These classes process the audio signals and suppress the reception of the image frequency (gnuradio-companion).

    

I use object-oriented programming with inheritance, using hardware interrupts to respond to switches and software interrupts to respond to touchscreen input. Some shell scripts help to establish communication between the two Raspberry-Pies (via LAN / TCP-IP) and the VFO (V24). LEDs and relays are switched by GPIOs. A connection to the internet is not absolutely necessary. My PYTHON code is about 8000 lines.


This touch-screen allows to document each QSO. If there is an internet connection, all QSO-Data will be sent to my server in ADI-Format to use with eQSL (http://www.eQSL.cc) or QRZ (http://www.qrz.com).


WSPR - on 20 m - 2,5 W - TX and RX mixed

My Homemade QRP-Antennas:

     

My Loop-Antenna for 20m and 40m and my Horizontal-L-Antenna (80m .. 10m)


 

 

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Dr. Bernd Kokavecz
Berlin Reinickendorf
21.11.2021