Pa0nhc magnetic active NVIS receiving antenna for the 80m band.
The connection system between the tuner unit and the antenna unit is developed by pa0nhc:
Only one thin 50 Ohm coaxial cable for transport of 3 voltages :
a. DC power
b. DC tuning
c. received RF signal
Professional made PCBs become available if i get enough demands :
- Mass planes.
- Screened signal tracks.
- Metalized vias and holes.
- Solder masks.
- Top silk (with component outlines and texts).
- All components are on the top. Tracks on the bottom.
- Small, unsusceptible antenna unit.
- Antenna PCB and ferrite coil fit in pieces 50mm (ALU/PVC) and 32mm PVC pipe.
- Remotely tunable. This version between 3,5MHz and 3,8MHz (the tuning range is adaptable).
- Antenna directive pattern is like a full size dipole on low height.
Maximal sensitive for signals coming from above (NVIS).
When installed rotate able, local noise source can much be weakened.
- Good sensitivity due to the use of an optimal ferrite rod.
- Very selective. Acts like a good pre selector.
- IMD-free, the specially designed electronics can handle very strong signals.
- The input circuitry is guarded against very strong field strengths like from lightning.
- Only one SMD transistor and one SMD diode. All other components have legs and wires.
- The tuning PCB has a build-in noiseless power supply, and fits inside a nice aluminum cabinet.
The PDFs below contain bottom masks for DIY PCBs. All mass points are interconnected.
The PDF parts list gives easy fitting components with ordering data (www.conrad.nl).
Some design details.
The sensitivity and selectivity are maximal due to the use of an optimal type ferrite rod. REM: a test with a balanced or screened coil gave much weaker signals.
Superb large signal properties are obtained by "Back-to-back" connected capacitance diodes, a FET source follower driver and the emitter follower output with large supply currents. The input circuitry is guarded against damages by fast switching diodes.
To prevent injection of noises from mains power lines, the tuner PCB is designed for maximal RF-isolation between the mains and
the 12Vdc output :
- All mains-related components are on the back of the unit.
- All other components are separated to the front side.
- The whole unit is NOT connected to the mains safety ground.
- On the output side of the line noise filter, the "ground" is connected to the housing of the tuner unit.
- The little mains transformer has separated chambers for pri. and sec.
- The rectifier diodes are bypassed with capacitors to prevent rattle and IMD.