2m Powerline show stopper

[VK2GOM]

I must be the most persistent radio ham there is, battling through all sorts of QRM on HF from home, but now the Powerline interference on 2m has ramped up a gear.

It is very broadband, right through the Band II broadcast band (although the commercial stations are strong enough to overcome it), all through the AM aircraft band, and right through 2m and beyond. It stops before 70cm.

I tried DF'ing it last night with a 4ele 2m Yagi, but the noise is so strong and close it wasn't possible to get a fix. I thought about using a stepped attenuator, but then someone on Facebook suggested building a switched antenna DF antenna device with an NE555, to generate a phase tone on FM and null on that for bearing finding.

I'm convinced it's a power pole again (but a different one this time), as the noise is the same as last time I suffered it, only far worse. Unless the ACMA come on board again to add weight on Integral Energy once I identify the pole, it looks like my 2m days are certainly over from home. And to think I had dreams of attempting QRP EME from the back yard

As far as the ACMA are concerned, I hear radio hams take low priority when it comes to being suffferers of interference.

A video of what it is like here now.

73 - Rob VK2GOM / GW0MOH

[VK3DXE]

See if you can identify a broadcast service that it affects at your QTH. That should give you a bit more weight.

[VK3AZZ]

Hi,
I have noise like that at home but only at night time and I traced it to the new 12V LED downlights in our family room.

Could that be a possibility at your QTH ?

Cheers,
Mal
VK3AZZ

[VK4TI]

I must be the most persistent radio ham there is, battling through all sorts of QRM on HF from home, but now the Powerline interference on 2m has ramped up a gear.

It is very broadband, right through the Band II broadcast band (although the commercial stations are strong enough to overcome it), all through the AM aircraft band, and right through 2m and beyond. It stops before 70cm.

I tried DF'ing it last night with a 4ele 2m Yagi, but the noise is so strong and close it wasn't possible to get a fix. I thought about using a stepped attenuator, but then someone on Facebook suggested building a switched antenna DF antenna device with an NE555, to generate a phase tone on FM and null on that for bearing finding.

I'm convinced it's a power pole again (but a different one this time), as the noise is the same as last time I suffered it, only far worse. Unless the ACMA come on board again to add weight on Integral Energy once I identify the pole, it looks like my 2m days are certainly over from home. And to think I had dreams of attempting QRP EME from the back yard

As far as the ACMA are concerned, I hear radio hams take low priority when it comes to being suffferers of interference.

A video of what it is like here now.

73 - Rob VK2GOM / GW0MOH

Have you run the radio off a battery whist shutting the whole house down setting a place to start , it might be a bad wall wart or other psu but you have to eliminate by closing things down and then starting one at a time , good luk with it

[VK2GOM]

Hi Mal, no the noise is not at home. With my current portable DF setup (Yagi and FT817 on batteries) there is no noise near home; it's only when I walk 100m or so down the road towards the suspect poles that the noise ramps up.

The reason the noise is so strong in the video is my base antenna (a vertical) is up in the clear and is line of sight to the problem poles.

I will report back more when I have pinpointed the offending source, after I've built a more accurate DF setup.

73 - Rob VK2GOM / GW0MOH

Edit: I just turned the house off at the main switch, and ran the radio from a 26AH battery. The noise is just the same. It had to be a quick test since our house powers the TV preamp/distribution system in the attic for us and the other 9 houses. If it's off for any length of time, they get angry at no TV reception.

[VK5IR]

I know its not a long term solution, but have you tried your radio's noise blanker?

I have the same powerline noise at home on HF but its about S7-S8 at its worst but my FT-840's NB cleans it up pretty well.

[VK2OMD]

...
73 - Rob VK2GOM / GW0MOH

Edit: I just turned the house off at the main switch, and ran the radio from a 26AH battery. The noise is just the same. It had to be a quick test since our house powers the TV preamp/distribution system in the attic for us and the other 9 houses. If it's off for any length of time, they get angry at no TV reception.

Good, an important test.

Pity isn't local, usually easier to fix.

In all of the video, I found a couple of seconds when the dial was stationary and you weren't talking.

There is a distinct periodic pattern of 10ms, though alternate peaks are different.

So, this (and the apparent broadband distribtion of the emission) shows the hallmarks of something derived from the mains, a signature like a lot of leakage sources (transformer bushings, cracked insulators, leaky surge supperssors.

So taking a Yagi out and looking for pole hardware on HV lines, transformers (bushings, surge suppressors) might yield result. BTW, those sources would probably not vary during the day (except perhaps for the effect of dew on dirty insulators).

Keep hunting.

Owen

[VK2GOM]

Thanks Owen. At least I am barking up the right tree - or should that be pole?

Theo: the IC910 noise blanker isn't all that great. It doesn't have much effect, if any. You can't tune the parameters of it like depth or width. It deals OK with pulse type noise, but as Owen's waveform shows, this isn't really pulse noise.

73 - Rob VK2GOM / GW0MOH

[VK3PY]

I had the same noise at my QTH. Noise blanker useless. DF'ed it to a specific QTH some 200m from my home. Turned out to be LED downlights. The "offending" householder acknowledged that he had to turn off the kitchen downlights when he wanted to watch TV! I suggested to him that his neighbours would be grateful for that too, as I would be. To his credit, the noise has never returned.

I understand that Mirabella had a recall on their offending products. There will be others.

Chas
VK3PY

[VK2GOM]

Chas, what was your DF technique? Just a Yagi and a receiver? Or did you use some sort of Doppler nulling setup?

73 - Rob VK2GOM / GW0MOH

[VK2OMD]

Chas, what was your DF technique? Just a Yagi and a receiver? Or did you use some sort of Doppler nulling setup?

73 - Rob VK2GOM / GW0MOH

In capable hands, a portable receiver and half wave dipole or small loop can be powerful tools. Though ambiguous, the sharp nulls are often the most usefull tools in getting a bearing for triangulation.

For my HF investigations, I use a 600mm square loop with balun on a ICR20 portable receiver. For VHF, the receiver with its telescopic whip is often enough to locate noisy power supplies, LED lighting power supplies, etc... but again a very small loop can help identify noisy components on a board.

If it is power line hardware and you can identify the pole, power utilities usually have quite sophisticated equipment for pinpointing faults like cracked insulators (often accoustically), loose hardware (sledge hammer) etc.

Your whole video said to me just two things:
1. the waveform when listening in a 2kHz slot shows 10ms periodic effects, with differences in the alternate peaks;
2. the emission is uniformly distributed over MHz.

(Gee, that was a lot more condensed than MB of video, and extracting a wav file from a Youtube video is non-trivial.)

1 hints involvement of power frequency, either solely or perhaps driving some kind of noise maker like a SMPS.

2 suggests is is less likely to be a SMPS because the emission from them would usually be clustered as sidebands around harmonics of the switching frequency.

Is the noise apparent on HF? What is the nature (no, not another video, just an intelligent analysis of waveform and spectral content).

Is ANY broadcast service adversely affected. If you are within the designated service are for the service, that may help in getting attention from ACMA and the maker of the emission.

Owen

[VK2GOM]

Hi Owen,

I have always had very bad local noise on HF, which appears to be from multiple sources including more distant powerlines and the general hospital just over the road, plus the usual switch mode PSU's and Plasma TV's locally. I'd be hard pressed to determine if there was any new noise on HF. Having said that, 40m is by far the noisiest, 20m slightly less so but still generally unusable, and 10m is just about usable some days.

The 2m noise doesn't seem to affect the local (Sydney) FM broadcast stations. Even with the inefficient antenna on our portable radio, the broadcast signal is far stronger than the QRM. The noise is only really evident in spectrum like 2m and the AM airband which should be quiet, by default.

Strangely, this morning, the noise on 2m stopped completely. IC910 S meter not moving. It had been going for at least 3 days solid, 24/7. I am now of course waiting for it to come back. If there is still no RF noise late this evening when there is no traffic about, I will take a walk out to the suspect pole again and determine if I can still hear the high frequency arcing/buzzing. It wouldn't be easy to hear it over the daytime traffic noise of the main Northern Road running adjacent to it during daylight hours.

73 - Rob VK2GOM / GW0MOH

[VK2CSW]

Is ANY broadcast service adversely affected. If you are within the designated service are for the service, that may help in getting attention from ACMA and the maker of the emission.

Owen

Don't forget to check the signals on the NFM stuff around 150Mhz. They are quite close to your trouble and might be being "interfered with".

[VK2GOM]

Hi Colin, I haven't heard anything in that 150MHz up band in English, and the only gear I can receive it on is ham radio equipment, so I doubt I could use that as just cause to speed the ACMA along.

That said, 2m is a primary allocation, to just ham radio - so why is it not afforded the same spectrum protection? Because we pay less isn't really a valid reason. We are not commercial entities like those stations with revenue..

73 - Rob VK2GOM / GW0MOH

[VK3PY]

Quoting Rob VK3GOM:

Chas, what was your DF technique? Just a Yagi and a receiver? Or did you use some sort of Doppler nulling setup?

Rob, I had a very good beam heading from my station 2m antenna. I plotted a line on that bearing on Google Earth just to see where it pointed to. I then took a 3-element yagi and my FT-290R for a walk after dark, heading on an intersecting bearing. As I approached the imaginary line, the noise rose quite strongly and peaked at the offending residence. As luck would have it, the house next door was unoccupied, which allowed me to walk up alongside the offending house, where the noise became dreadful. Just to be sure, I walked across the road and took several bearings from various positions along the street - no doubt about it, I had the right place.

When I confronted the householder I had with me the flyer from Mirabella (see attachment). It turned out that the noisy downlights were indeed Mirabellas, but even had they been some other brand, having an official-looking piece of paper in your hand that proves such lamps can be a source of RFI lends you some street-cred.

Chas
VK3PY

[VK2AZ]

Strangely, this morning, the noise on 2m stopped completely. IC910 S meter not moving. It had been going for at least 3 days solid, 24/7. I am now of course waiting for it to come back. If there is still no RF noise late this evening when there is no traffic about, I will take a walk out to the suspect pole again and determine if I can still hear the high frequency arcing/buzzing. It wouldn't be easy to hear it over the daytime traffic noise of the main Northern Road running adjacent to it during daylight hours.

Probably gone because it rained during the night - just wait a while for the dust to settle again

BTW, I pass your QTH everyday on the way to work, and park my car in the next street - I work at the Hospital.

Hilary
VK2IUW

[VK2OMD]

I must be the most persistent radio ham there is, battling through all sorts of QRM on HF from home, but now the Powerline interference on 2m has ramped up a gear.
...

Ah, perhaps you would be attracted to a low noise antenna! That sort of magic would be just what you and lots of us need.

The LFA (Loop Fed Array) Low-Noise Yagi is very different from the traditional dipole fed Yagi in many ways with its primary benefit being unwanted noise rejection. The LFA has a rectangular shaped, full wave loop driven element that is laid flat on the boom between and in-line with the parasitic elements . Then there is the way in which the loop functions. The smaller end sections which run parallel to the boom, are engineered to be 180 degrees out -of-phase with each other. This provides the same effect as is seen within ladder-line feeder; each side cancels the other out and therefore, minimum radiation occurs.

Don't get your hopes up, it can't selectively reject noise whilst accepting desired signals in the general case.

The cancellation explanation plays to a dumbed down ham audience that believes that ladder line does not radiate, but ladder line with nearly half wave spacing (as in the case of those end sections of the LFA DE) radiates very well. If you had a good product, why would you make perposterous claims... unless it is effective in selling product.

Owen

[VK2GOM]

I have already built a nice 7ele LFA for 2m. I use it out /P now and again in field day contests.

It has decent performance. I think their 'low noise' claims are from a G/T (Gain to system noise) point of view, not susceptibility to power pole noise!

73 - Rob VK2GOM / GW0MOH

[VK3PY]

Quoting VK2OMD:

Ah, perhaps you would be attracted to a low noise antenna! That sort of magic would be just what you and lots of us need.

Guffaw.......!

Touche' Owen!!!

Chas
VK3PY

[VK2OMD]

The LFA (Loop Fed Array) ... Then there is the way in which the loop functions. The smaller end sections which run parallel to the boom, are engineered to be 180 degrees out -of-phase with each other. This provides the same effect as is seen within ladder-line feeder; each side cancels the other out and therefore, minimum radiation occurs.

If we consider a square loop of sides one half wavelength, the above ladder line explanation would suggest that since the current in one side of the loop in magnitude but 180° out of phase with the current in the opposite side that there would be complete cancellation of each other, and the same would apply to the other pair of sides.

But in fact, this is a quite popular antenna on HF, a full wave loop operated on its second harmonic.

Above is the free space radiation pattern from a square loop of sides one half wavelength in the plane of the loop. The gain varies from -2.5dB to +2.5dB.

The ladder line cancellation explanation given by InnovaAntennas for their loop where the sides are almost a half wave apart is plainly nonsense.

This is not to suggest that the LFA might not be a good antenna, but that if it is, it is not for all the reasons given by InnovaAntennas.

Owen