Discussion in 'Amateur Radio News' started by G4TUT, Oct 2, 2019.
I contribute to the IARU so David Sumner can fly to the meetings and still feel useful
Maybe the IARU will do what the ARRL won't/can't. Hope springs eternal.
For those who missed it, this thread in the QRZ General Technical Q&A forum < a year ago covers an interesting QRM incident. It's a long but good read.
Link ---> 75m Phone Wide Interference/Jamming
The story in the thread starts out with general assumptions and misidentification of the interference as being OTHR etc, ie, the usual suspects. The sound it made was incredible.
After some hams got busy gathering RDF evidence through KiwiSDR TDoA, other hams put boots on the ground and reported, then others applied that info to some good investigative thinking and browsing, and the likely culprit was narrowed down to a surprising source.
It seems to have be coming from the vicinity of Penn State University where academic research activity was being performed using a QRO RF drying kiln for curing lumber, as this article explains.
I have not seen complete confirmation of that as yet, but after being reported to the FCC, and a few investigating hams making calls to various professor hams at the school, the RFI suddenly stopped.
Ironic, or perhaps just a mistake too embarrassing to admit.
Power supply, motor, and LED companies usually don't design-in any EMI suppression from the beginning of their project.
They only add RFI suppression parts if they are forced to, because the added parts cost lowers their profit.
Once upon a time, I was a mid-level RF Design Engineer at the RF division of a big electronics corporation.
The company was more well known for its other division, which at that time, manufactured about 75% of the world's switching power supplies.
Even though I wasn't in the Power Supply division, every so often a power supply engineer would show up at my RF lab with a sob story.
"Hey, Bonnie, our new XYZ-123 power supply failed FCC. We can't meet our production schedule. You gotta design us a quick EMI fix. The product release date was supposed to be last month, but the whole factory line is stopped. We have 50k finished units sitting there that need the EMI fix re-work."
But, they never asked for EMI RF design advice until after they had already finished their power supply product design and sent it to production.
They thought that the process of "FCC Lab" test measurement of the radiated and conducted emissions required a completed product, and EMI was a random roll of the dice.
There is something backasswards about that kind of a design and verification process, but it still exists to this day.
I hope that someone clamps down on all the interference being generated by "cheep" and sometimes poor designed electronics being imported into our country. Although I see that they have not made much progress on those non FCC type accepted HT's (another topic all together) so I don't want to get my hopes up quite yet. The noise on the bands is much worse today than it was 30 years ago that's for sure. (Well, we did have that pesky woodpecker until it got radiated). Where is it all coming from? Many times its right in your house! Faulty components in appliances, lights, etc. Other times it is coming from equipment and machinery being used in hospitals and factories nearby, just to mention a couple. I don't see an end to any of it unless someone decides enough is enough and the research begins! I like the story and end results W0PV shared on the possible interference from PA State on 75 meters. It shows that there could be a positive outcome to some of our noise problems if everyone can work together. Hope the IARU can help. By the way, has anyone driven past any of these "electronic" billboards or scrolling electronic signs? My dualband vhf/uhf rig gets S9+ interference from them. A loud open squelch hash noise that is enough to make ya want to turn off the radio! Or use PL on the receive frequencies so long as the repeater has PL on it's output. I live in a rural setting and a small town nearby that has these signs lined up and down the main street. Out of 10 signs, 9 of them generate RF noise on VHF and sometimes UHF. There's only one I know of that doesn't. Could it be that they all have power supplies made in China? I think the one that I don't get an interference from must have a decent power supply in it. Made in USA? Best 73 to all
In February, while you were sitting behind a keyboard arguing that symbol rate restrictions are good things, Dave was at the Conference Preparatory Meeting, moving the ball on 47 GHz toward continued exclusive amateur use and away from the last die-hards who want to reassign the band to high density terrestrial mobile.
I know; I was there.
The IARU and the rest of the amateur radio community
need to join forces with other users that are affected by radio interference and noise, because alone we are not taken seriously.
A close ally may become the radio scientific community, and also the military radio users.
Commercial users also are becoming concerned about interference from electronic equipment, as there has been interference reported on aviation and public safety VHF and UHF frequencies.
However, on lower frequencies, the interest is spotty at best.
Recently, I have been involved in studying the interference potentials from LED-based lighting appliances and billboards, and also from solar energy equipment on behalf of the National Transport Authority.
Preliminary results show that current certification requirements are not sufficient to fully protect weak-signal VHF communications.
Also, the aggregation aspects of having large amounts of appliances within a small volume have largely been overlooked.
This does however only take into account equipment and appliances that actually fulfill the CE or FCC certification requirements.
Unfortunately, many appliances today carry "fake" CE markings, and are much worse than the requirements.
On HF it is highly unlikely that any support could be obtained from the Authorities. Their general view is that HF has become patently obsolete.
The last bastion probably was the German Authorities that into recent times enforced HF receiving interference complaints with the justification that freedom of information also required foreign HF broadcasts to be received reasonably interference-free.
In later years, this policy was abandoned due to lack of interest in HF broadcasting.
In most countries, amateur radio EMI complaints have the lowest priorities. Resource priorities and a general weariness of radio amateurs are among the reasons.
Here, have a cookie.
Stop China from exporting its crap to the world that would be a step in the right direction. Well until some other country starts doing it in there place.
The main problem is not China exporting, but other being so cheap that they are buying the products.
Very few consumers (and a fair share of professionals) are prepared to fully pay what EMC compliance really costs...