active NVIS receiving antenna for the 80m (and other) band(s).
The use, copy and modification of all info on this site is only
permitted for non-commercial
If a link does not work, then the item was renewed by me. Remedy : first press F5, and try again.
- Unsusceptible antenna unit.
- Much smaller size than a rotate able dipole antenna or loop antenna.
- Antenna directive pattern is like a full size dipole on low height.
Excellent NVIS antenna when for 80m or 160m or 40m..
If rotate able, noise sources within short range can be "nulled".
- Very selective. Acts like a good pre selector.
- Good sensitivity due to the use of an optimal ferrite rod and Hi-Z FET input.
- IMD-free, the specially designed electronics can handle very strong signals.
- The input circuitry is guarded against very strong field strengths like a local transmitter and nearby lightning.
- Remotely tunable with :
Super simple (one coax) connection between tuner unit and antenna unit ( developed by pa0nhc).
- This version tunes between 3,5MHz and 3,8MHz.
- But the used ferrite rod is optimal for high-Q antennas between 0.1 and 21 MHz.
- The antenna PCB fits in a piece of 50mm (ALU or PVC) pipe.
- The antenna ferrite rod fits inside a piece of 32mm PVC pipe.
- The antenna PCB contains a coax mantle current choke.
- The tuner unit contains a noiseless power supply and an optimal mains noise filter.
- The tuner PCB fits inside a neath and cheap Proma ALU enclosure.
- The PDF parts list gives suggestions for perfect fitting components, with ordering data for "www.conrad.nl", and component details for other suppliers.
New designed, military grade PCBs. See : "Available PCBs"
- Double sided
with on both sides mass planes for clean signals.
- With wide top and bottom inter connecting vias.
- No cooling profiles needed. All SMD semiconductors are contact cooled by soldering hem directly onto the PCB plane.
- All parts soldered on top plane
- Enlarged SMD solder pads for easier soldering.
- Optimal combination of through-hole and SMD components
- Green top and bottom solder masks => NO undetected short circuits.
- White top silk with clear component outlines and texts for easy assemblage.
by others, schematics below do not contain component IDs nor
- both PCBs contain top silks with all component IDs.
- a complete component IDs list will be send to you together with ordered PCBs.
Correct placing of components should be easy.
REM : If Conrad.nl does not sell to your country, please do use the component details mentioned in the ordering data below, or from the Conrad site, for ordering from other suppliers.
Some design details.
The sensitivity and selectivity are maximal due to the use of an optimal type ferrite rod.
REM: a test with balanced and a screened coils gave much weaker signals.
Superb large signal properties are obtained by "Back-to-back" connected capacitance tuning diodes, an optimally setup source follower buffer/driver with a very steep single gate MOSfet, and the emitter follower output using a very high-Ft UHF transistor.
The input circuitry is guarded against damages by fast switching diodes.
An on-board mantle current choke blocks noises coming from the coax mantle.
The antenna unit PCB (not at the
BNC-bus) should be grounded directly onto a
noise free grounded mast.
tuner unit has a build-in noiseless power
supply with mains noise filter.
To prevent injection of noises from mains power lines, the tuner PCB is designed for maximal RF-isolation between the mains and the DC-output :
- All mains-related components are on the back of the unit.
- All other components are at the front side.
- The whole unit is NOT connected to the mains safety ground.
- The "ground" connection at the output side of the optimal type mains noise filter, is connected to the (grounded) housing of the tuner unit, not to the with noises polluted mains safety ground.
- The little mains transformer has very small parasitic coupling capacitances, due to separated chambers for primary and secondary windings.
- The bridge rectifier is a low drop type, with all diodes bypassed with capacitors to prevent rattle and IMD.
- Both PCB sides contain screening ground surfaces.
and safety (your own responsibility !) :
Your mains power group should contain an automatic ground current leak detecting safety switch.
IF the antenna
unit PCB is grounded to a noise free grounded mast :
the receiver and the tuning unit should NOT be grounded, but only be "grounded" via the coax cable to the antenna unit.
IF your antenna PCB is not
The tuner unit, and the connected receiver, should all be connected to one noise-free ground.
As the unit contains a mains noise filter,
including filter capacitors, a little ground leak current will flow.
To protect static sensitive equipment, and avoid an unpleasant feeling when (dis-)connecting cables, i advise you to plug the 240Vac mains cable only into a wall socket, when all other cables are connected.