Hardware Projects


speech processor

One of my first amateur radio projects was the construction of a dynamic compressor in 1976. This small additional device is looped into the microphone line and gives the voice a higher "assertiveness" during SSB operation. Today, this technology is already built into the tranceivers.

dynamic compressor


10GHz waveguide technics

Inspired by the book "Amateurfunkgeräte für das 10-GHz-Band" by Josef Reithofer (DL6MH), I started to build 10 GHz components based on gunplexers / waveguides. After, thanks to the company UKW-Technik in Baiersdorf, the procurement of WG-16 waveguide material also in small lengths was possible, I built various gunplexers as well as single-ended, push-pull and blow-through mixers. Gunn diodes from Valvo or Microwave-Associates were used in the oscillators. Mixer diodes of type 1N23 or 1N415 were used in the mixers. These parts could be purchased, at affordable prices, only at flea markets. The following pictures give an impression of this nostalgic technology.

10GHz waveguide technics (Gunn diode - compared in size with a match head)   10GHz waveguide technics (Mixer diode)

10GHz waveguide technics   10GHz waveguide technics

10GHz waveguide technics   10GHz waveguide technics

10GHz waveguide technics (Test oscillator)   10GHz-waveguide technics (Test oscillator)


test oscillator with attenuator

In the "UHF-Unterlagen" Volume I/II by Karl Weiner (DJ9HO) a fixed signal generator for RX alignment up to 5.67 GHz is described by Michael Kuhne (DB6NT). The oscillator oscillates at 28.8MHz and the output signal can be attenuated to inaudibility by a built-in attenuator (Preh 0-1 GHz capable).

Test oscillator with attenuator   Test oscillator with attenuator


DCF77 evaluation board

In the "Praxisheft 2" of the AATiS the circuit of a time signal receiver DCF77 by Helmut Pape (DK2ZA) is described. This circuit, which is built on a Euro-board, is ideal to understand the technology of time signal transmissions and to fathom it with own experiments.

DCF77 demonstration module   DCF77 demonstration module



Also in the "UHF-Unterlagen" Volume I/II by Karl Weiner (DJ9HO) a SWR meter (reflectometer)is described, whose coupling element consists of a piece of coaxial cable, into which two coupling loops are pulled. This SWR meter can still be used up to the 23cm range.

reflectometer   reflectometer


RF sniffer

A rectifier diode and a small amplifier are mounted on a brass bracket. This small tool can be used for the detection of high frequency.

HF-Sniffer   HF-Sniffer


BayCom packet radio 1k2 modem

With the advent of PacketRadio in amateur radio, the BayCom group was formed. This 1k2 modem was first operated with a C-64 computer and later with a PC under DOS.

BayCom Packet Radio 1k2 modem   BayCom Packet Radio 1k2 modem


RTTY filter converter

This RTTY filter converter is based on the technique of operational amplifiers. Turning potentiometers, which are switched over by a step switch, are provided for the different shelves. A variable shift is made possible by the external helical potentiometer. With the toggle switch the shift position can be switched from normal to reverse. The converter is designed for connection to a C-64 user port.

RTTY filter converter   RTTY filter converter


SSTV modem

The following OP741 based comparator is the only hardware to decode FAX or SSTV with programs like JV-FAX.

SSTV Modem   SSTV Modem


80m foxhunting receiver

I built the kit of the 80m foxhunting receiver to participate in the DARC E29 OV fox hunts.

80m foxhunting receiver   80m foxhunting receiver


144MHz foxhunting receiver

I bought this 2m direction finder receiver at a flea market for 5,-DM. After the necessary restoration I participated with it in OV fox hunts in the district Hamburg and Schleswig-Holstein. (but always according to the motto "to be there is more important than to win").

144MHz foxhunting receiver   144MHz foxhunting receiver


dummy load

A 50 ohm terminating resistor is important for alignment work on transmitter stages. The following pictures show two different models. The left one has a built-in rectifier diode, which allows relative power measurements up to 10Watt at 430MHz. An empty condensed milk can serves as housing. The right model consists of a resistor network in a brass tube. The tube is filled with thermal paste, which transfers the RF power converted into heat to the brass tube.

dummy load   dummy load


RF probe

From the "UHF-Unterlagen" Volume I/II by Karl Weiner (DJ9HO) comes the construction proposal for this RF probe. The electronics are built into a felt pen in the left model and into a mechanical pencil in the right model.

RF probe


simple test oscillator

In a long discussion with Klaus (DL2HAD) the idea arose to build a simple test oscillator for 48MHz with an oscillator assembly from computer technology. The harmonics are ideal for measurement purposes at 144MHz and 432MHz.

simple test oscillator   simple test oscillator


TenTec 50MHz transverter

With the release of the 50MHz band for amateur radio, the company TenTec has brought a 6m transverter on the market, which I bought as a kit and built. Unfortunately I drew a blank at the "lottery" of the 6m licenses.

TenTec 6m transverter   TenTec 6m transverter


analogue AF notch filter

Based on OP741 operational amplifiers a AF filter was described in the December 1997 issue of the magazine "funk". This technology can certainly not keep up with today's DSP technology, but my device still does its job on a FRG-7000.

analogue AF notch filter   analogue AF notch filter


weather RX

Through the initiative of Hein (DL6LAY), 5 weather receivers were set up in winter 2002/2003 at our DARC chapter. With the help of the appropriate software weather pictures can be received, represented and evaluated over the sounding map. Further information can be found on the website of the DARC club M21.

weather RX   weather RX


SDR Softrock evaluation board

Inspired by a lecture about "Software Define Radio" I found the experimental board SoftRock5 at the American QRP group. With this small board the SDR possibilities on 40m and 20m can be tested well. The first impression with simple software like Rocky was convincing. This is clearly the Zunkunft in the receiver technology.

SoftRock50   SoftRock50



At the HamRadio 2008 I bought the kit of a Kent Squeeze Paddle. The following pictures show step by step the different stages of the assembly.

Paddle Paddle Paddle Paddle Paddle Paddle Paddle Paddle Paddle Paddle Paddle Paddle Paddle Paddle
Click on the photos to zoom them!


telegraph relais paddle

The following photos show how to build a paddle from a Siemens telegraph relay.

telegraph relay telegraph relay telegraph relay telegraph relay telegraph relay telegraph relay telegraph relay telegraph relay telegraph relay telegraph relay telegraph relay telegraph relay telegraph relay
Click on the photos to zoom them!


soundcard interface

To avoid hum loops between the computer and the radio, galvanic isolation is required. The easiest way to achieve this is to use two AF transformers. The following picture shows the setup with two transformers and a level adjustment.

The interface can be used for all digital transmission modes.

soundcard interface   soundcard interface schematic
Click on the schematic to enlarge it!

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QRSS beacon

Inspired by a Soldersmoke Podcast I build a QRSS Beacon. The meaning of QRS is „Send slower“ and based on this QRSS signifies very slow speed CW. In this case a dit needs 1 second and a dah 3 seconds. To key the callsign DB/BN you need about 1 minute. The beacon consists of 3 main units: the CW controller based on a AVR Atmel ATTiny45, the transmitter kit Genesis Q5 and a low pass filter. The beacon can transmit in CW and FSK and can produce 500mW Output on 10,140 MHz.

QRSS beacon in its case   top view of the QRSS beacon   bottom view of the QRSS beacon   operating the QRSS beacon at a GAP Titan DX   DL2HAD receiving the QRSS beacon (about 10 km)   G4CWX receiving the QRSS beacon
Click on the photos to zoom them!

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