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Pa0nhc improved version of
pa0rdt "Miniwhip" active wideband receiving antenna.
20200215
(C)
The use, copy and modification of all info on this site
is permitted, but only for non-commercial
purposes, and
thereby explicitly stating my radio amateur call sign "PA0NHC"
as the original writer / designer / photographer / publisher.
Youtube
video presentations :
English
version
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To prevent un-authorized commercial
copies, NO component details are given in the schematic diagrams below.
No Gerber nor PNG PCB files will be provided.
All copies sold at other sites, which refer to my call, and for details to my
internet site, are illegal.
Installing parts should be easy for
experienced builders.
Both parts lists will coincide with the white PCB topsilk imprints and part
placement drawings.
Construction details, test data and de-noising instructions are given in the
downloadable texts.
Bandwidth : 5kHz to 148MHz +0/-3dB.
Sensitivity :
- Using the internal antenna surface only : abt. -17dB.
- With added external 1,5m x 1cm antenna rod : abt. -12dB.
Input RF impedance abt. 7 Mohm // 6pF.
Input DC resistance 22 Mohm.
Includes over-voltage protection.
Output impedance : 50 Ohms asymmetrical.
This version Miniwhip :
Is an excellent DX antenna for vertically polarized wide band reception of :
VLF,LW,MW,SW,FM broadcast, airplane band and 2m amateur
band.
However :
=> Between 1.8MHz and 7MHz, the reception of regional signals
(20-400km range) will be weaker. <==
The Miniwhip is NOT an NVIS antenna (like every vertically polarized antenna).
IMPORTANT :
Every active receiving antenna
needs careful de-noising measures.
E-field antennas (like this Miniwhip) also must be connected to a dedicated noise free
ground.
1. Most effective CMC if wound with firmly
twisted, or paralleled 0.5mm lacquered wires.
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2. Coax version. |
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LATEST
UPDATES.
20200208
Antenna unit.
Common mode choke L5 :
a. For best results ONLY use #31 ferrite (high
loss Ui=1500).
Core : 29 / 19 / 12.5 mm (FairRite item 26 31 80 12 02 -
Mouser.com).
Wind until the core hole is filled.
Every turn must lay beside the former as shown below.
Do NOT cross another turn.
Best choke :
Picture 1 : two
firmly twisted, or two paralleled, lacquered wires 0.5mm.
This will have a characteristic
impedance of 50 Ohms AND largest choking impedance.
OR
One twisted wire pair retrieved from an UTP cable.
Mind "plus"
and "minus".
Check the insulation between
:
wires and wires,
and
the wires to the core.
Picture 2 : THIN coax, RG174 or RG316
--------------------------
Splitter
unit.
b. Insert an extra choke between the PWR+ connection on the
PCB, and the power+ connection on the PWR-bus.
Choke construction :
Wind as much as possible turns thin (0.25-0.5mm lacquered wire) in the
hole of a :
small FairRite #75 core 26 75 62 64 02 (high Ui=5000)
OR
small FairRite #31 core 26 31 48 01 02 (high loss Ui=1500)
c. Do NOT connect the PWR-minus on the
PCB.
The PCB mass planes must electrically only be connected to the INSIDE of
the splitter box
via the 3mm screws.
d. The power bus and BNC buses MUST all be fully
metal
and
installed in perfect electrical contact with the OUTside of the box.
e. Use CMC's on all cables (see de-noising)
f. GROUND the antenna PCB, nothing else.. |
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The influence of temperature changes in Common Mode Chokes.
20200530.
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Unique pa0nhc antenna input circuit for highest IMD-free output, widest
bandwidth,
and a wideband output circuit including an effective common mode choke.
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Measured frequency
characteristics.
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50kHz - 30 MHz.
The -2 dB dip at 15 MHz is a weak choke resonance in the
splitter.
Orange = nanoVNA Ch0 reflection damping
(70cm coax, 50 Ohm // 3p5 coupling).
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50 kHz to 200 MHz, -3 dB @
147 MHz.
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