wide band (DX) receiving antenna.
Preliminary development data.
You need a clean,
12V to 14V, 120mA external power supply.
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.
MODs for PCB #13 :
- 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.
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).
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 ==>>).
2. hanging on one (plastic) screw through h1
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
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.
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:
(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.