That dreaded QRM

This is something old that I kept on editing when things progressed. I just put it here for the records and hopefully not for future reference.

That dreaded QRM that popped up in last year’s WW SSB (note: that’s the 2014 edition) seems to be gone for now. At least in its nastiest form. Knock on wood. There might be a general increase in noise since I first put up a wire here in 2003. I think. I haven’t got actual measurements to prove that. Since the fierce QRM came suddenly a year ago I have been very focused on noise. I may hear high noise levels now that might not even be there in reality. I don’t know what is acceptable by nature.

It’s hard to find the source of a problem if it isn’t always there. It only occurred when it was dark outside so I concluded it was most likely related to either a street light or a neon sign. But I live in a rural village with little commercial activity and the closest neon sign is 1.3 km away. Another thing I noticed was that it didn’t start together with the street lights. Nevertheless it went away at or about the same time the lights went out in the morning. Last fall, about a year ago (fall 2014), I went up to the shack evening after evening for a while to listen but it never showed up. So I gave up. But in a contest after sunset, it sometimes started wiping out 80 completely, rendering 20 useless. It affected 160 and 40 but those bands were still manageable. It was hard to listen through it in CW and it killed my ears in SSB. I never heard it when listening (RX only)  at random times. Yet it was almost always there during nighttime in a contest. So I started to think I triggered the QRM source by emitting 1 kW of RF power.

During the IARU HF Championship 2015 the QRM was there when I was running USA late in the evening. There is a street light on a pole about twenty meters from the tower. I can see it through the window from the corner of my eye when looking at the PC monitors. Suddenly that light went out and then the QRM level dropped significantly. The light came on a few seconds later and along came the noise. It happened a second time somewhat later. This more or less confirmed my theory that I activated the QRM by putting out RF myself. Don’t ask me if or how it’s possible.

I was glad I finally had something to blame. But I was (and still am) not really sure that was the real culprit. Both neighbors to the left and right have those aquarium lights in their fish tanks. And what if someone around here has grow lights for some purpose? What about some new TV sets? Those devilish power line adapters the ISP’s put everywhere? People watch TV at night. But probably not as late as the time of the QRM. It had to be something related to darkness as it wasn’t there in broad daylight.

But that particular streetlight wasn’t really broken and it’s hard to report ‘a street light that might possibly cause QRM on the HF bands and sometimes goes out just to come on again by itself’. The utility company’s technician might think I’m pulling his leg. I briefly considered a slingshot to shorten the lifetime of the bulb. But that’s not my style. A double barrel rifle? I’m one of the few around here without a gun so that would require an accomplice with aiming skills. And deaf neighbors.

July 31st. By coincidence there was another flickering light on the other side of the garden. Also about thirty to forty meters from the tower. I completed an online form to report broken streetlights. I do that often when I see a flickering light in a wide radius around the QTH. The power company usually fixes these lights within a few days. So one summer evening just after dusk the utility technician came with his truck-mounted cherry picker. He parked and blocked the street. That’s why they come at night. Not to hinder traffic. I saw the guy climbing in his elevator basket and up he went. I rushed down the street to tell him about the light and my specific problem. I couldn’t care less that my street is a dark hole and that the lamp is totally broken. But it mustn’t flicker. Try explaining ham radio and short wave reception and QRM to a stranger in a few words. The kind technician was very cooperative. He agreed to wait up high on the pole while I went in to check for noise after he replaced the light bulb. Which is a problem because the noise wasn’t always there and popped up at random times only. After replacing the lamp and visually inspecting it he told me that it was a very old model showing its age, making it prone to flickering and arcing. Let’s hope he and my hunch are right.

Later that summer I got hold of ON3DI’s spare FT-817. Thanks for that OM. I walked around on a couple occasions, with the TRX on a strap over my shoulder and holding a piece of wire in the air. Since it was dark I put on a fluorescent safety jacket. People passing by slowed down and looked at me from their cars as if they had seen an alien. I went up and down and around the block but I didn’t really capture that specific QRM. Not then and not on the transceiver ever since that one particular light bulb got replaced. So I’m keeping my fingers crossed.

A few weeks ago there was another bulb flickering. Just across the street, about ten meters from the living room. And another one three hundred meters from here. And another one almost one kilometer away. They have all been replaced by now. I guess the guy processing the online street light trouble tickets knows who I am by now.

There is one problem that has been there for years that I might track down one day. It’s audible on 20/15/10, loudest on 15 meter and it becomes very loud when I turn the beam from the Caribbean to PY. So when at 300° (USA) it is weakly there but it doesn’t block signals. It gets louder at 270° to become very loud at 230°. It’s not really a show stopper, more a nuisance. Signals sip through. And the yagi is not often pointed beyond 300°. I also noticed this noise when walking around with the FT-817. It’s loud at my front door. And that’s at 270°. That’s also where the coax for broadband and digital TV is. And at 270° there is a coax tap on the pole across the street. By the way: The Panasonic TV makes a lot of noise around 21 MHz. I followed the coax wire in the house to the TV, that’s how I found out. The TV noise itself goes away completely on the FT-817 when I pull the 230V power plug out of the socket. That’s when I’m standing next to it. I should listen in the shack on the yagi and then detach the AC power. But the TV noise is not the other noise I pick up. That noise has been there for ages, even in the dark ages of the vacuum tube TV, long before the LED TV.

Somewhere someone recently said that antenna restrictions won’t kill ham radio but switching electronics will. Well, it doesn’t have to if the design and construction is done right. By accident I came across this item by ON7EQ. Scroll down and look at the last picture. EMC? What EMC? Damn you spectrum polluters! 

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