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pa0nhc 0,1-28MHz active wide band (DX) receiving antenna.
201701017
This is a vastly improved version of the pa0rdt "Miniwhip" active receiving antenna.

Preliminary development data.
(C) The use, copy and modification of all info on this site is only permitted for non-commercial purposes, and
thereby explicitly stating
my radio amateur call sign "PA0NHC" as the original writer / designer / photographer / publisher.
Sets of 2 PCBs are available (with transistors at your wish).


 

You need a clean, 12V to 14V, 120mA external power supply. 
A design for a little, noise- and rattle free power supply, is
HERE 


Left : Miniwhip antenna PCB glued into top end cap, ferrite choke (2x5 t - 2.8mm coax) and red grounding wire, all going into a 25cm x 50mm PVC pipe with end caps.

Link does not work ? Press F5 and try again.

Download the PDF parts list 20170909 HERE.

See also the bottom of this page for important installation advises.


Location of C14

MODs for PCB #13 :
1. C10 must NOT be placed. Leave C10 open.
2. C14 (100p NP0) must be soldered onto the PCB bottom surface, see photo ==>>
3. For L1 do not use 4.7 uH, but instead place a wire link.
Tip: 
If you mainly are interested in VLF reception :
C4,7 must be 0.47uF film,
L2,3 must be 1mH (low Ri, 200mA or higher).

           Properties :
- Fully class A circuitry, clean reception without IMD.

- Output IP3 (7 en 8 MHz) +35 dBm, IP2 (1MHz) +45 dBm  ( ! ! ).

- New version 13, improved circuitry for T1
- Only 0.6dB insertion loss, for higher sensitivity.
- PCBs with enlarged SMD solder pads for easier heating and solder flow.
- Now using commonly available new type very hi-Ft UHF transistor for T2.
- Biggest strong signal handling, max output 2Vrms (!).
- All commonly available parts, only two SMD components.
- The cleanest reception possible if well installed.
- Really wideband with R/C coupling to the receiver, no transformer.

 


    For which signals is the Miniwhip useable ?
The Miniwhip is a vertical positioned antenna. The following properties are valid for all vertical antennas :
- Good results for the reception of VLF / LF / LW / MW / SW short distance ground wave communication.
- Good results for the reception of SW signals at distances over 300km (DX).

The Miniwhip is (like all vertical antennas) NOT suitable for NVIS, that is for the reception of signals of distances UNDER 300km between 3.5MHz and 7.2 MHz..

 


        Listen DX at :
The broad band webSDR at the university Twente (50kHz to 30MHz).
They use a "Miniwhip".

        Highly recommended to read :

Theory about the practice of Miniwhip antenna (written by pa3FWM).



Ready to install.


Antenna PCB glued into a end cap.

        Updated antenna and power circuit.
New version schematics :
1. setting optimal steepness for T1.
2. T2 now is a commonly available modern UHF hi-Ft SMD transistor.

3. R13 is normally a wire bridge.
Exchange it for a 47 Ohms resistor, if T2 should oscillate due to mismatch and unfavorable length of the coax cable.

4. The splitter unit is fused and zenered against damages
if a short circuited coax cable, over voltage or wrong power polarity occurs.

Both PCBs are now double sided.
The splitter PCB is best installed into a shielding metal box. 



The antenna PCB must be installed vertically, in a non-screening, fully closed, rain resist housing.
For instance a 40mm dia. gray PVC pipe, abt. 35cm long, fully closed with top and bottom end caps.

The antenna surface "ANT" must be FULLY ABOVE the metal mast.
The top of electronics surface (C5) should be at the same level as the mast top, or above it.  
"GND h2" must be connected to the noise free grounded mast via a thick wire.

Highly recommended : Leave 13V power always on. Then the internal power dissipation (2Watts) prevents condensation.

The PCB  can be :
1. Glued into top end into a PVC end cap (see photo ==>>).
or
2. hanging on one (plastic) screw through h1
or
3. Screwed at h1 and h3 with distance bushes.

 



When placing the splitter PCB into a metal box, use at each screw h1 and h2 two extra M3 nuts as spacers between the PCB and the box.
For stable mechanical and grounding contact also use tooth locking rings :
1. under the outside flanges of both BNC bushes, and
2. under the M3 PCB top nuts.


The antenna surface (10cm upper part of the PCB) must be fully ABOVE the top of the antenna mast.
Grounding hole h2 must be connected to the noise free grounded antenna mast.

C10 must not be placed. In stead C14 must be soldered onto the PCB bottom surface.
It must be connected to the hot ends of R1 and R11.
See component list.




Assembling.

WARNING: carefully check the type and value of EVERY part, BEFORE soldering. Measure resistors using a digital ohm meter. Removing later on can be difficult.
 
- Solder wire bridge R13 on the bottom plane of the antenna PCB. Prevent a short circuit with ground. Wire ends may not be above the top copper surface.
- Solder all resistors.
- Solder all ceramic capacitors.
- Solder all film capacitors and the fuse holder.
- Solder the elco's and the coils.
- Solder the BNC bus onto the antenna PCB. Check for short circuit between R13 and ground.
 
Take anti- static measures, and prevent over heating while soldering the transistors.
Solder fast with little solder, and let cool down after every single solder connection.
 
- Solder on the PCB bottom surface the MOSfet T1. REM : see the broad pin (drain). The FETs legs are bend down towards the solder pads on the PCB.
- Solder on the PCB bottom surface the SHF transistor T2. First solder the three small pins, and as last and fast the broad cooling fin.


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:

The complete Miniwhip antenna+splitter+power supply may only be grounded at the antenna pole.

Disconnect the ground wires at the receiver and the 13.6V power supply.

Be sure you are protected by :
an automatic ground-current-leak-switch in the mains supply line.

ALSO :
Before connecting plugs, install hi-Ui ferrite material on the beginning and the end of every cable.
Wind cables several times through the ferrite hole for far more effectiveness.
3 times through the hole = 9 times more effective than 1 time straight through the hole!

TIP : useable and cheap ferrite rings:
Conrad NR 534480
(Ui=10.000, remove the insulating shells).
Conrad NR 500683 (Ui=5000, Epcos B64290-L618-X35)
Epcos has more suited ferrite rings (ui=5000-10.000) in different dimensions.


(Earlier version antenna PCB).
Here a sample of a mantle current choke. As much as possible windings through a HI-Ui ferrite core (Ui=8000) will block noises coming from the coax cable.
Use thin coax for maximal number of turns possible through the ring core.
Three times through the hole = 9 times more effective than one time straight through the hole.

==>> The ground plane of the PCB, should at h2 be connected to a noise-free grounded mast. Use a thick wire.