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Simple noise free stabilized power supply 230V~ input to 12Vdc / 130mAdc out.
A perfect companion for the miniwhip active DX antenna.
pa0nhc.nl .  Parts list and text update 20190511.

This simple little power supply is designed for powering noise-critical instruments, like a Miniwhip active antenna

It can be left switched-on, day and night, thereby preventing condensation in a small outdoor instrument, like the Miniwhip antenna.

It is a well filtered linear circuit, therefore contains no switching circuit, and does not generate any HF-noises. It can  become a little warmer than an SMPS, but this is entirely normal.

Although a double sided PCB is available, a printed circuit board is not strictly needed. See "haystack construction" below.

The PCB is designed for installation into a Hammnond 1254JGY ABS box. With two solder able horizontal PCB connectors, one for AC mains voltage, and one for 12Vdc output.

The specified transformer Tr1, and the low drop stabilizer LM2940IMP-12 are both short-circuit-proof. A fuse is therefore omitted. 
As the LM2940 is virtually indestructible, and gives better performance..
D1 (1N4000) It is only needed if a 7812 is installed. It is omitted when an LM2940 is installed. 
C7 is changed from 100n for 7810, to 47uF/16V low esr, as specified for LM2940.

Rectifier Br1 is now a TS140S SMD low drop rectifier. It  fits at the same location, and is bypassed by four capacitors to prevent rattling noises and cross modulation caused by possible penetrating RF signals. 

Both low drop components will give some extra "headroom'",  and a bit better performance (higher maximal output current).

RF filtering is accomplished by two optimal common mode chokes, wound on 29 mm ferrite cores, which are especially designed for this task (ONLY use FiarRite mix #31 cores !), and 100nF ceramic capacitors. F1 and F2 should be wound with as much as possible turns. As currents are small, use for F1 (240V~) well insulated THIN twisted wire. For F2 could be used twisted lacquered 0.5mm transformer wire.

In stead of a DIN output bus, a more standard 5.5mm DC bus could be used.

If a lower output voltage of 10V can be used, use a LM2940CT-10 low drop regulator.

        Miniwhip.
In my Miniwhip, a bit lower supply voltage to the antenna PCB taen 12V only effects the maximal output voltage, and the consumed supply current. Normally, this should not have any effect on reception quality.
But remember, over a long thin coax line between splitter and antenna, already some voltage drop will occur.


Schematic for PCB v15.
Download the schematic for PCB v15 HERE. 
Download the parts list for PCB v15 / 20190511 HERE


This updated PCB V15 is available.
Double sided factory made PCB including mains- and 12V connectors.
This PCB fits into a Hammond 1554JGY ABS box.
At F2 : Observe - / + at both sides.
DIN connector pins 1,4 are "-12V",  pins 3 and 5 are "+12V". Pin2 is Not Connected.
This output connector could also be a wire connected standard 5.5mm chassis DC bus.

 Stabilizer IC1 = LM2940 SOT223 low drop. Added:C8
Br1 can be a SMD TS140S low drop. 
C7 is at least 22uF / 16V.
D1 is not fitted for IC1=LM2940.
See text.


(Earlier version PCB V12 with 7812 stabilizer)
For F1 and F2 : 
At least 12 turns thin twisted wire through 29mm FairRite mix #31 cores.
See text.

        Simple construction.
The C7 Euro connector mains cable is connected to a C8p PCB bus which is soldered onto the PCB.

The 12Vdc output is from a 5 pole DIN PCB bus, for connecting to a DIN audio plug (1-2 = minus, 4-5 = plus).
REM :
you also could install a standard 5.5mm DC jack, 2.1mm pin Conrad Nr  733946 into the side of the box, and connect it with wires to the PCB.

Before installing te PCB, four fully plastic bushes at the mid of each side must be removed. Use a 9mm drill in a table drill stand
- Use a 9mm drill to drill de round parts of the plastic bushes down until flat with the bottom
- Break the remaining plastic flanges away using pliers.

As currents are small, you should use thin, well insulated (stiff) wire for chokes F1 and F2. 
-  For these common mode chokes, use only cores from FaiRite with #31 mix. 
-  Before winding, firmly twist the the wire pairs at 1 turn each 2cm.
-  Wind F1 and F2 close to the body of the core.
-  Wind as much as possible turns, close near each other (not over each other).
-  Fix the ends coils to the core body by means of plastic straps or hot glue.

Drill a few 10mm holes into the long sides of the box to allow some airflow cooling.


Hole for a DIN bus.
If a 5.5mm DC bus will be installed, a 0.3" or 7.7 mm hole should be drilled. 

 


If no PCB is to be used (haystack construction).

If enough room is available, use a bigger transformer, bigger elco, and a fuse. This enhances the maximal output current.
If a lower output voltage of 10V can be used, use a LM2940CT-10 low drop regulator.

A metal cabinet is not needed. A cheaper ABS box will do.
You could glue transformer, Br1 upside down to the bottom of the box.
Glue C5 at its side to the bottom of the cabinet, leaving its vent free.
Use thermal glue, or quick hardening two component glue. 
Before gluing, roughen the bottom of the box a bit.

-  All connections and coils can be made using thin but well insulated wire. 
-  Screw IC1 on 10cm2 2mm thick aluminum surface for cooling.  REM : the IC1 cooling surface is connected to its - 12V connection.
Use for IC1 ONLY a low drop LM2940CT-12 (TO220). 
-  IMPORTANT : Please do use C6 only with the stated value 470nF, to prevent oscillations of IC1.

The ceramic capacitors should be soldered with the shortest wires possible directly onto the pins of Br1, IC1 and the DC output bus..

    Wire the following connections to a  common ground point, which is the middle pin of IC1 :
a. Connect the minus of elco C5 only to the middle pin of the LM2940CT-12.
b. Connect the minus of rectifier Br1 only to the middle pin of the
LM2940CT-12
c. Connect the minus of output core F2 only to the middle pin of the
LM2940CT-12

Drill a few 10mm holes into the long sides of the box to allow some airflow cooling.