Simple noise free power supply 12V / 185mAdc
This simple little power supply is suited for use with a Miniwhip active antenna. It can be left switched-on, day and night, to prevent condensation in the antenna circuit. It has no noisy switching circuit, therefore does not generate any HF-noises.
A small transformer, a bridge rectifier and a 3-leg stabilizer do all the work. Bridge rectifier BR1 is bypassed with capacitors to prevent rattling and cross modulation caused by penetrating RF signals. High-Ui (5000) ring cores F1 and F2 block possible RF signals on the input and output cables.
Transformer Tr1 and stabilizer MC1812 both are short-circuit-proof. A fuse is therefore omitted. For housing, a Hammond ALU cabiner type 1590S, 1590C or 1590N1 is suited.
Schematic with Conrad orderNrs.
IC1 is screwed onto the flat surface of this PCB for cooling.
!! At screws S1-4 do use standoffs between PCB and the metal casing for 10mm distance !!
On the bottom copper, after soldering cut all wires in the 230V~circuit down to 2mm.
Connect "Out -12V" also to the metal cabinet.
Bottom copper mask 600DPI for a DIY pcb.
Although given here, a printed circuit board is not needed. Both transformer and 4700 uF elco can be glued upside-down onto the bottom of the cabinet, using fast hardening two component glue. Both MC7812 and Br1 can be screwed onto the inside of the box, using a bit heat conducting compound. The other capacitors should be soldered with very short connections onto Br1 and the 7812. All other connections can be made using thin insulated wire.
The 230V~ mains cable should be protected against pulling by a strain relief. The output can be a wire with plug or a jack mounted into the wall of the box. As currents are small, use thin mains and 12V cable, as this can be wound several times through the hole of the ferrite cores F1 and F2 for optimal choking effect.