Interference from power transformer

[moo9]

I am a passionate Radio Amateur on Shortwave (with license, callsign etc.). I get high level Interferences from a transformer install right next to our house. Strange enough the strength of the interference is usually lower in the daytime, but increases at night. Our village has about 20 - 30 houses and two transformers. Could the noise generation be related to the charge / energy consumption, which increases in the evening when everybody returns home?

I can't work on Shortwave due to the high interference level. I am considering to contact PEA, but one never knows whether they care about. However noise, sparking etc. means loss of energy, so may be this is an argument, as they lose energy nobody pays for. Also a faulty grounding could be the reason. What would be a reasonable approach to the PEA. As we know the producer of the transformer, we could also ask their technicians to do a check (which, depending on the costs, we would pay). In case they find a problem, they would approach the PEA and this should improve changes that they replace or repair the transformer lines.

Cheers

EDIT I've split this out of the electrical earthing thread as I think it deserves its own answers, any EMC experts out there?

[Crossy]

I'm no expert on EMC (my degree is in Electrical and Electronic Engineering), but I can throw in a few ideas

Field strength follows a cube-law, so simply re-siting your antenna further away from the source of interference may be sufficient.

I found this an interesting read http://www.energy.siemens.com/hq/pool/hq/p...formers_EMC.pdf although it concentrates on the design of the transformer to minimise EMC issues.

I don't think you'll have any joy with PEA, they have enough trouble understanding that a supply that varies between 160 and 240V is less than satisfactory

Thoughts anyone?

[genset]

Hi Moo9,

As a former HF operator, I'd like to offer a couple of comments and pose a few questions.

I always operated in remote areas and never erected an antenna remotely close to an electrical transformer, but a transformer such as this will add noise to your HF signal proportionally, according to proximity, rating and load (as will vehicle engines, generators, SCR based loads etc). As the load on the transformer may be greater during the evening hours this may account for the increased noise.

I don't believe PEA will be able to solve this problem for you, re-siting or shielding the antenna should be your first consideration. A few questions if I may:

• What type of antenna are you using; omni-directional whip, sloping wire, half-wave dipole...?
  
• Is the interference present on all frequencies between 3 and 30Mhz
  
• What distance are you communicating over and are you using ground wave (within Thailand) or sky wave (within Thailand or multi-hop to elsewhere on the globe) as your preferred propagation method?
  
• Are you using voice or CW (Morse) to communicate?
  

It may seem counter intuitive from an 'enjoyment' perspective, but working through the noise which is always present on HF (regardless of the additional transformer noise) is a fun challenge and being able to do so effectively represents the skill of a HF operator. If you cannot move your antenna and have to live with the noise (as carrier wave (morse) can be used to communicate on the noisiest of signals (QRK-1)), my suggestion would be to explore other areas of HF comms (if you haven't already done so). I always found the challenge of balancing antenna design, frequency and signal strength selection, to bounce signals between the earth and different layers of the ionosphere (multi-hop) thousands of miles and leaving a footprint where my target was located to be enormously satisfying. I think I still have a Morse training program on one of my computers (random 5 character group and plain language generator at speeds from 1 to 30wpm) and I would be happy to send you a copy and give you some advice if you wish to learn, PM me if you are interested.

Cheers, Genset

Edited February 27, 2010 by genset

[IMA_FARANG]

I am NOT an expert on this but just some points:

1. Strange enough the strength of the interference is usually lower in the daytime, but increases at night. Our village has about 20 - 30 houses and two transformers. Could the noise generation be related to the charge / energy consumption, which increases in the evening when everybody returns home?

Answer: YES....if the transformer is causing the interference by arcing...the more current running thru it, the more arcing....and the more Radio frequencey Interferece (RFI) generated.

2. What are the supports of your antenna tower/structure? Are they metal (wire)? If so, the RFI generated sees those metal wire supports as antennas. You need to break the support wires up so they do not act as antennas to absorb that RFI and re-radiate it into your antenna system. There are RFI filters you can build/buy that can be put into the antenna support wires, and should help remove the RFI to ground/earth. If you can find a American Amatuer Radio Relay Leauge (AARRL) manual (the bible for Radio amatuers in the U.S.) they will probably have articles on how to construct RFI fliters. Unfortunately, nobody execpt real hard-core hams actually BUILDS any radio equipment today....it is just bought from the electronics store.

3. If your using an antenna coupler, something as sinple as enclosing it in metal box with the outside of the case grounded MIGHT help to remove or lower the RFI. But be sure the antenna coupler or antenna won't short out on the metal case.

4. If your radio is capable of it, you might be better off running in Upper Side Band (USB) or LSB, rather than striaght AM on the shortwave bands. It would probably increase your signal to noise ratio on the recieved signal versus the RFI. I had a Sony shortwave radio I ran off a sinple long-wire antenna...I found that I could get shortwave broadcast staions quite well on the USB mode with much less RFI.

5. You might be able to buy/build a sort of pre-amplifier for the Shortwave band, which would also increase your signal to noise ratio.

6. Ideally, the local electric company should be interested in fixing that arcing transformer...because it does waste energy. But I bet in Thailand, they won't bother. It's always worth a try anyhow.

Edited February 27, 2010 by IMA_FARANG

[tjo o tjim]

Do you have a spectrum analyzer to tell where the noise is? There are reasonably cheap gauss-meters out there such as this: http://www.omega.com/ppt/pptsc.asp?ref=HHG191. Not sure where to get in LOS though. With a meter, you can better determine the exact source and magnitude of the problem.

[elkangorito]

The noise you are experiencing sounds like insulator or hardware failure (& not a transformer problem). Check the sounds at the below link;

http://www.rfiservices.com/sound.htm

Most "housing" distribution transformers in Thailand are fed by 22kV. I'd also bet that if you took a walk under the power

line at night, you will witness (hear) arcing across more than one insulator & may even see some lovely blue sparks or flashover.

This problem is usually caused by faulty equipment, pollution or moisture. Most energy authorities treat these problems seriously because if they are not addressed, bigger & more expensive failures can result.

This is only one assumption. I think it would be a good idea to ensure that the RFI is not coming from within your home

first.

http://knol.google.com/k/overhead-line-insulators#references

If the RFI is created by insulator or hardware failure, there is not a great deal you can do to block or reduce the noise.

The faulty equipment must be repaired/replaced to eliminate the problem.

Are you using a transceiver or just a receiver? I used to be an amatuer radio op in Australia.

Good luck.

[moo9]

Thanks for all the interesting replies! My antenna is a Yagi Beam, about 21 m high on a tower which has a 2 m deep concrete foundation. All is properly grounded. The antenna is about 10-12 m above the suspected transformer and about 10 - 15 m away horizontally. I already checked the surroundings of the house with a heldheld scanner on 135 MHz AM and found that most noise is coming from the pole where the transformer is located. So this should be the major noise generating source.

I am transmitting and receiving, mainly talking to friends in Europe (usually SSB but also some digital modes like PSK31). The noise is wide spread over 3 - 29 Mhz, even still receivable in AM over 100 MHz, but with lower strength for sure.

I am using a noise cancelling unit I ordered from the US, which works fine, however also reducing the strength of the desired signal.

I understand, that the PEA would not be much interested in following up this. I try to find some insite contacts at the PEA to help me out. Let's see whether I can make them move. Maybe it is not the transformer itself, but some arcing from faulty ground or insulators (I assume this, as the transformer is relatively new / 3 yrs or so and looks ok).

Why everybody is giving up HAM radio nowadays? It is such a nice hobby. Certainly it is much easier to use Skype or a messenger for communicating, but it is no challenge. It is so interesting to learn about antenna design, propagation and all that stuff, but aparently this is not of interest of the newer generation (although I am not that old, but I was growing up with CB etc. and hold the ham license for more than 25 yrs now).

As we say, vy 73's :-)

[elkangorito]

Transformers hardly ever cause the problems you are suffering. I'll bet my left knacker that the problem relates to faulty insulators &/or surge protectors. They may just need to be cleaned.

You can try the following link re PEA power problems;

http://www.pea.co.th/th/eng/page.php?name=hotline

Re amatuer radio, I had a couple of great old rigs...Collins KWM2, Racal, FT101B, FT707. I used to make all my own antennas & matching gear. I was particularly fond of rhombic antennas (large but fantastic).

73's de ex VK2NRC & VK3APP (RAAF Laverton).

[moo9]

Update:

PEA Pattaya nor Chonburi have equipment to measure EMC noise, so they can not help directly. Trying to contact some transformer producers in BKK who can measure the noise, but no feedback so far.

Well. seems that will be a long struggle! Luckily least noise in the North / Northwest so I can enjoy tallking to some friends in Europe and the US.

73's

[genset]

21m tower and 2m deep concrete foundation... I guess you won't be in a rush to try to re-locate that then...

Given your comments and if the readability of the net is QRK 3 or less, I would again recommend CW (especially if you appreciate the challenge), you will also discover an active and passionate niche community within the larger community of ham enthusiasts. There is a good reason why morse continues to be taught by military units around the world; in the event of a significant EMP which would disrupt or disable most contemporary communication systems, the dots and dashes of chopped up carrier wave will continue to work through the most difficult conditions. I found the software programme I mentioned in my previous post, it's 7.5mb in size, if you want a copy PM me with your email address and I'll send it to you.

Cheers, John.