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Author Topic: Power line noise makes operating on the move impossible  (Read 4320 times)

Posts: 0

« on: November 26, 2011, 04:08:47 PM »

I luckily received an MFJ 9020 SSB rig through the post, (not stopped by the Thai customs for a change), and I've been able to complete my mobile installation, with 200 watt RM amplifier and 20 meter Hustler resonator on a DX Engineering 24 inch mast and Breedlove NMO mount.

I've added many earthing straps and I've had good QSOs with stations out to 5,000 km whilst parked up.

I mentioned in a previous post about the alternator hash/whine.  I added a 'brute force' alternator hash filter and reduced this considerably, but total elimination will have to wait until I can get a new alternator.

But whilst driving my car, I've found that it's impossible to have QSOs, due to the high level of noise from the power lines that run adjacent to most roads, (both 220 volt and high power 3 phase lines).  If I manage to find a minor road with no power lines, then the noise level drops significantly and QSOs are possible.

Is this a unique problem to power lines in Thailand?  Is there anything that can be done to reduce the level of received noise from these power lines?  Otherwise, I can only make QSOs whilst parked up.


Posts: 1485

« Reply #1 on: November 26, 2011, 04:15:52 PM »

Simon, I don't know what can be done about it, but it's certainly a problem (at least, for ME), in the USA.  There's a small part of my regular 24mile drive home (36km?) where the road runs parallel to high-voltage transmission lines, and I get S7 noise on that part of the drive.  I almost never work anybody from that area--so if someone tells you how to make the noise better, I'll be reading over your shoulder!   I'm glad to hear you're getting your mobile rig so well set up!

Posts: 52

« Reply #2 on: November 27, 2011, 04:24:50 AM »

I experience a similar problem driving in and out of the city. Fortunately i can often avoid tose routes. You might try a Timewave ANC 4 noise canceller. I've used one at home and it worked ok. I am not  sure about how well it would work in a mobile installation though.

Good luck



Posts: 9930

« Reply #3 on: November 27, 2011, 12:02:11 PM »

I live in Northern California, there i a streach of road  betwen my town and the next one north which is down in a bit of a hole and has many power lines  parallel to the roadway.  I have almost no radio in that 5 mile streach, even on a 2 meter repeater.  so yes they do make a difference, as you have found.  try going down near the ocean, or on top of a hill and see if it will help.  As far as just driving, you will have to live with it, I think.  Good luck

Posts: 422


« Reply #4 on: November 27, 2011, 12:25:51 PM »

Interference from power lines is problematic and there is not much you can do at the receiver.  I imagine in Thailand, being mostly tropical, corroded hardware probably is a wide spread issue, and is the root cause of your problems.  As another person noted, the only semi-effective filter out there is a JPS (now Timewave) ANC-4.

The ANC 4 does help, but not eliminate this particular problem.  However, it is really designed for use in a fixed station, as it requires a decent sized sniffing antenna to detect the interference.  Another issue if trying to use the ANC-4 mobile, when you move from place to place, the phase of the interference will change. Each change, will require that you retune the ANC-4, thus you will probably end up spending more time fiddling with the ANC-4, than looking for contacts.


Posts: 1418

« Reply #5 on: November 29, 2011, 09:25:19 AM »

Yes Simon, that is a another gremlin while operating mobile. I have it all the time here in Texas. I have found that the bad hardware can radiate quite a distance. it doesn't have to be next to the road you are traveling. Age, and damage of the hardware, plus sloppy install jobs are the culprits. Sitting in my driveway, the power line noise is higher than my ignition noise. I can't test, check for ignition noise without moving to another location.

There are some places I drive the power line noise is S9+20. If I know I will be going through there, I better finish the QSO. Not much an amateur operator
can do about it. Just find the quiet spots in your normal travel area.

I will add the cities are the worse. Open highway gets better. Out in the boonies with no power lines for a mile or more is the best !

You need a storm to come along and take it ALL DOWN ! Then it will have to be re-built.

73 Tony N5UD /M

Posts: 2575

« Reply #6 on: November 29, 2011, 12:57:54 PM »

Usually it is caused by corona discharge at the line insulators. If you live in a place (or country) where they do the bare minimum work to keep electrical service functional you will find many spots where the noise level is prohibitive.

For many utilities it means climbing the pole or using a bucket truck to replace the bad insulator. Usually they get dirt tracking or microscopic arcing at the bottom side of the insulator (where all of the ridges are). In some places they will only fix the problem when the insulator fractures (blows up) or shows an obvious electrical arc that can be seen from the ground or starts a grass fire.

Usually at a well operating utility they are proactive about hunting down these leaky insulators as the affect reliability and power quality. When a line crew tears out a bad insulator it is usually put in the dumpster as soon as the truck gets back to the warehouse. I have seen "other" utilities that stockpile the insulators and try to clean them up, do a rudimentary test and put the insulator back into the parts bin to go back out into the field.

A pole insulator costs anywhere from $50 to $5000 depending upon the voltage, physical size, etc... High tension towers that may have a dozen insulators in series, suspending a few thousand feet of wire are really expensive.

Beyond that, loose hardware, corrosion or misapplied components can be noise generators. Usually loose hardware will burn up or blow up under load. Someone using the wrong sized crimp splice or not prepping the connection can cause arcing. Trees and branches against the wires can make a near constant noise and only stops when the tree catches fire or a ground fault detector trips.

The worst I have seen was a set of high voltage bushings on top of a 161 KV transformer in a substation. They had to let that problem go on for more than a month because it was a custom part. One time I had a single phase surge arrestor blow up like a bomb and drop the bus onto the steel support in a yard. It embedded big chunks of this pineapple sized protector in the ground in all directions out to almost 50'.

In poorer countries where there may not be a mandated maintenance standard it may be almost impossible to get anyone interested in the slightest to your power line noise problem.

Ms. Tisha Hayes, AA4HA
Lookout Mountain, Alabama
Free space loss (dB) = 32.4 + 20 × log10d + 20 × log10 f

Posts: 1003

« Reply #7 on: November 29, 2011, 01:41:23 PM »

General noise level for me is very high here in SoCalif, and it's 1/4 mile to the nearest power lines, but there are LOTS of them around. On HF, I have to use the digital Noise Reductino on my 746Pro pretty much all the time, and it helps a lot. An external NR unit on your MFJ radio might do as well.
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