How to eliminate computer RFI

As promised at other friend’s blog here is the solution I made to eliminate computer RFI.

The main culprit was due to parts saving to lower computer PSU selling cost, and the part is the AC line filter (Schematic diagram below). This filter was supposed to block the switching noise from entering the AC lines and thus entering the radio through the radio PSU.

Double coil filter

The cure is simple, just add the missing filter.

Unfortunately it is not easy to buy or find one in our Indonesian market.

However all is not lost, you can make one yourself  and install it in the place where it was supposed to be. Locate the icon of two paralel coil just after the input circuit from the mains before the main rectifier (you can see the two jumpers). Remove the jumpers and insert the double coil you just made to replace the jumpers.

You have to experiment on the toroid core available to make the filter, normally I found out that 30 turns for each coil will be enough to suppress the 45 KHz noise and it’s harmonics.

The other way is to find a junk functioning external AC line filter (the one with the same input socket as the original power suply mains cable) and replace the original power inlet socket with the junk filter and connect the output of the filter to the mains input of the computer PSU PCB.

One last tip to remember is beware if you r using an old CRT monitor, you may get the same problem from it’s switching PSU.

However please use the standard saftey precautions (remember there are lethal voltages inside the PSU when connected to the mains) and do this at your own risk n may u have a nice contest time with your favorite software.

vy 73 de YB6LD Donny

 

The South East Asia 40m problem, do we want to resolve it?

Any ham radio operator who has operate ham radio here in South
East Asia knows that the 40m band is a band where you have to compete for operating space. Well until late next year we still have our 100KHz allocation which is actually not too bad. However if one works on CW he or She will surely have to compete with the illegal stations operating USB from fishing boats and timber/plantation settlements.

In the 60’s and 70’s where analog VFO’s are the domain there were less illegal stations, but now with the advance technology one very easily obtain a relatively cheap amateur radio transciever for commercial purposes and without a license they just find a frequency they like to operate.

Those illegal stations never feel guilty of breaking the laws and in fact they feel they have the sole right to operate just because they can buy a radio and push the PTT button. What make’s it worse is the authority seems to let them operate illegally without any actions.

When the new WRC regulations come to effect next year (2009) we the CW operators still cannot benefit from the regulations that the IARU has fought for many years, why? just because we will stay at the lower part of the band where the illegal staions play around.

If we want to improve the situation I suggest that we urge and write to our National Ham radio society/association to contact the authorities of each of our countries and also IARU and present them with the situation. Tell them that they has in fact lost income from licenses fees that should go into the government income form those stations. At least if they return they has contributed to the government.

I believed that every ham radio station have to pay a certain amount of money for their license, why do we allow those illegal staions operate without paying any fees and creating a lot of QRM??