DL1DXA.de :: QRP :: Home-made Projects
Here is a short summary of some of my QRP and self-made projects
Actually, I built my first QRP transmitter in 1958 consisting of a Colpitts oscillator with the
tube 6V6 and a power amplifier with the 6L6 tube followed by a Pi filter as
antenna tuner. Unfortunately, there are no pictures anymore.
This noise bridge is a very helpful device for measuring impedances
or the resonance frequency of antennas in the shortwave range.
It consists of a noise source with a Z-diode followed by a broadband amplifier.
The bridge balancing circuit, in the true sense of the word, consists of toroidal core of Manifer Mf343 and
makes use of the station receiver, tuned to the frequency of measurement, as a detector.
The bridge is balanced by changing a bridge capacitor and resistor while listening to the receiver for a noise minimum.
Resistance and reactive values can be determined from the variable R and C positions, and may be converted to an SWR or Z value.
This PCB holder is very helpful. The PCB can be turned by more than 210°.
It is applicably for PCB sizes between 25 and 220 mm.
- 1983: 2m transistor PA 50 W
At that time, it was a little bit difficult to build a VHF transistor PA in the medium power range. This PA was designed with a Russian power transistor.
-
1984 (80m CW/SSB QRP TCVR):
The transceiver is based on a
single conversion concept with an IF of 200kHz using two mechanical
filters with 500 Hz and 2.7 kHz bandwidth.
The whole transceiver is completely equipped with parts made in the former GDR.
- 1984: Bias Tee with N-connectors
This self-made bias tee is used for remote power supply of preamplifiers and converters via the coaxial cable. It can be used up to 2.5 GHz.
- 1985 2m FM TCVR (5W Output)
This home-made 2m FM TCVR is equipped with an TDA1047 in the RX.
In the former GDR, each transmitter has to be inspected and released by the "Deutsche Post".
After the inspection test, the TX got a mark transfer consisisting of the callsign and a consecutive number.
This SWR bridge is developed especially for the 23 cm band and is
based on a microstrip dual directional coupler design.
As a special feature, the forward wave as well as the backward wave can be depicted simultanously.
- 1986: Braodband amplifier
This broadband amplifier can be used for the 23 cm band to compensate cable attenuations.
This was my first poject using SMD parts.
This prescaler, with a division ratio of 64 or 256, expands
the input frequency range of your counter to 1.6 GHz.
The sensitivity is < 10mV for 3 - 1300MHz and < 50mV for 1 - 1600 MHz. Dimensions: 80mm x 20mm x 25mm. Input impedance: 50 ohms.
In 1987, I became qrv on 23 cm with this TVTR and a homemade PA with two tubes 2C39 (abt 120 W out) and a homemade 5m long Yagi Uda antenna.
At the end of the eighties, packet radio became very popular.
At that time, I built a couple of PR modems.
This is hybrid solution for both packet radio and RTTY. The AFSK signal is generated with an XR2206.
For demodulation, a filter converter ist used for RTTY
and an PLL demodualtor with the XR2211 for PR.
- 1988 PR Modem for both VHF and HF
This is packet radio modem for both VHF and the shortwave where
the world chip AM7911 with an integrated equalizer is used. PTT and computer are separated by an opto-coupler interface.
Last Modification:
