Pa0nhc 0,03-30MHz active broadband (DX) receiving antenna.
- New version, using modern BF998 and a BD139 semi conductors
- Real class A circuitry, clean reception without IMD.
- One coax connection.
- Easy soldering : only one SMD part
- PCB grounding connections have thermal relief lines
- Broadband R/C coupling to the receiver, no transformer
With advises for cheap and effective de-noising ferrites
You need a clean, 13.6V / 150mA external power supply, fused at 0.2A.
A design for a little, noise- and rattle free power supply, is here.
Please read :
Theory about the practice of the Miniwhip antenna (written by pa3FWM).
You can listen to :
The broad band websdr at the university Twente (50kHz to 30MHz).
They use a Miniwhip.
As the MINIWHIP is vertically polarized, it is NOT suited for reception of NVIS signals.
It is well suited for wideband reception of signals below 2MHz and DX signals above 3MHz.
Regional signals on 80m and higher therefore will be received weaker.
For this project you canNOT anymore order the PCBs. All are sold-out.
PDF masks for DIY printed circuit boards :
Antenna unit BOTTOM copper PDF
Antenna unit TOP copper PDF
Splitter unit BOTTOM copper PDF
Splitter unit TOP copper PDF
PDF parts list including
Please also read on this page information about alternative components, adjustments and installation.
PDF construction and installation instructions
IMPORTANT : For T1 do NOT use a Jfet.
T1 MUST be a MOSfet, as it must :
- have a low input capacitance and
- be able to draw 40mA peak (!!)
IMPORTANT : T2 should have a high Ft.
The used BD135/137/139 is a NPN audio driver with high Ft (>= 190MHz).
You could also use a 2N4427 or 2N3866 with a cooling star.
Two 2N5550 in parallel is also a possibility. Select two equals from a larger batch.
R3 and R8 could be replaced by a small ferrite bead (for lower self-noise).
ZD1 protects some types T1 against to high supply voltages.
Factory-made splitter and antenna PCBs, ver.20160701 (NOT available anymore).
The antenna unit should be installed vertically.
After installation, all PCB surface above T1 should be ABOVE the top of the mast !!
Do not install the antenna surface in parallel to the mast.
h2 must be used to connect the antenna unit directly to the noise free grounded antenna mast.
h1 can be used to hang the PCB on a 50mm long M3 screw which is drilled through the plastic pipe.
The total value of R2 + R2a depends on the transistor type used for T1.
The drain current of T1 (20mA) should be adjusted by replacing the bridge at R2a with a resistor.
Adjust its value so, that Ur4= 3.0V +-10%. Try R2a=1Mohm first.
MOSfet T1 is soldered on top.
A BF998 tetrode can be soldered with both gates soldered to island "g1+g2".
If a BF999 triode is used, it must be positioned upside-down.
REM: The connecting islands for T1 are big enough to solder older types dual gate MOSfets with its legs (BF961/982/40673).
|For your own safety, place a 0.2A fuse in series with the +12V
Every antenna performs as good as its installation permits it to.
- For max. sensitivity :
- this antenna should be positioned as high and free from metal conductors as possible
- the ground plane of the PCB must NOT be lower than the top of the mast
(the connecting trace between the electronics and the antenna surface, and the antenna surface itself must ALL be ABOVE the top of the mast).
- For best signal-to-noise ratio :
- install the Miniwhip onto a well grounded mast
- connect "GND" of the Miniwhip PCB (h2) to that mast
- place HI-Ui ferrite cores (Ui between 3000 and 10.000) on the beginning and end of all cables, to block cable noise currents (see below).
For best noise free reception:
Be sure you are protected by :
TIP : useable and cheap ferrite rings:
Here a few windings through a HI-Ui ferrite core (Ui=5000 to 10,000) block noises coming from the coax cable.
3 times through the hole = 9 times more effective than 1 time straight through the hole.
==>> The ground plane of the PCB should be connected to a noise-free grounded mast at hole h2.