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

 

OC-270 Simuelue after my last visit in 2006

It has been quite an emotional trip returning back to visit Simuelue Island after 2 years operating the OC-270 for the first time as YB1BOD/6 and friends,

Many things has changed including the new airport building and a longer runway, new hotmixed road from the airport to the town of Sinabang and of course new buildings rising up.

I’m fortunate to stay at a newly build hotel with the air-conditioning facilities and there are now 3 cell phone company operating (Telkomsel, Indosat and Pro XL).

Unfortunately I did not have the opportunity to operate ham radio since this is a short job assignment with an NGO at a remote sub district of West Simuelue at the village of Malasin.

The Malasin harbour

If I returned back next time I will be able to provide the IOTA chaser an opportunity to get an OC-270 confirmation (hopefully).

It is a nice place to enjoy nice fresh salt water fish but you have to cope with the limited electricity (only at night) at least for the time being.

Will miss the food and hope to return again next time, de YB6LD Donny

 

YB land, beware of electrical spikes

October 10, 2008, it was a bad morning. Since 04:30 in the morning local time the rain pours down heavily and there are constant blast of lightening.

However since I know that my computer and radios are switched off I feel confident that nothing would happen, right?

Wrong, my ups are still on standby and connected to the mains supply.

After the rain stopped, as usual I try to connect to the internet but then the computer did not want to be switched on while the monitor standby led flashes meaning that something must have gone worng with my computer.

I try to investigate and snif arround and I smell silicon burnt!! Bad sign.

When I look further inside the case I found that the smell comes from the power supply. My guess is correct, the power supply was damaged (the switching transistors are burnt along with several diodes). I wonder why it happened since the ups are sound functioning.

Further investiagations lead me to a damaged motherboard, but luckly the hard disk and the DDR memory are still functioning well so no data were gone.

Lesson learned:

1. Never leave your mains supply connected after you finish using your computer. Use a double switch to disconnect the mains, don’t think that spikes can only goes through the hot cable.
2. Always disconnect your telephone line (including your DSL connection) when there are lightening strikes. That is another way the spikes enter your sensitive electornic equipments.
3. Do not trust your spike prevention circuits/device. I use a reputable APC UPS with an anti spike prevention circuit but it did not help (at least in my case). Better be save rather than regret.
4. Check your electrical ground system, make one if it is not available. Most of the house build in this country did not follow the rules in electrical installation (to save the contractor’s money).

Even though you never experience what I have been through I urge you to learn from what happened to me, and I hope this will be the last for me.

To our authorities: Regulations are made to save expenses and please do not think that what happened to others are completely isolated, we live in a connected world, what happened to others somehow will have an impact on us sooner or later.

 

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??

 

Sun spots where are u?

As we have been told by the experts, we have passed the lowest part of the sun spot cycle, and we are now at the start of a new sunspot cycle, however the band conditions are not yet favourable for me (at least). With my lowly rotatable 4 band dipole (40, 20, 15 and 10m) I find it still very difficult to get the attention of those dxpeditioners, amateur radio contests are a chore for me, with luck and CW I’m able to get few rare prefix on 40m but again I have to compete with illegal stations on the lower edge. No government seems to be interested in reducing the illegal staions operating USB on the CW portion of 40m. I long for the days of when 20, 15 and 10 meters are open nearly all of the day, but when will the sunspots are coming?? God knows