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[KB1SNJ]

hi all, I have an AA5 tube AM radio that i really like using, and it picks up what sounds like AC hum from the antenna. Is there a 60HZ antenna blocking filter that I can use?

I tried making a loop antenna wuith a short coax feedline but it really didnt attenuate it.

Thanks!

[AA7IS]

You're not getting 60 hz through any antenna connection. DE AA7IS

[KB1SNJ]

I'll post video later. When I touch the antenna it gets louder along with the strong station. Theres a buzz QRM on my property think it's the main powewr line from pole to my house not sure. When I turn into my driveway, car AM radio hears it.

Anyway this AM tabletop gets as strong a buzz as it does the station.

Since it quiets down when i disconnect the antenna, how is it not coming into the antenna?  Sure seems like it is

[N1UR]

You are not getting 60hz at your antenna connection.  You are getting noise on the AM broadcast band frequency that is created by 60hz powerline creating an interfering signal on you listening band. It sounds like a buzz but the frequency is not the sound.

So you can't "filter it out".  You have to find it and mitigate it at the source.

Many of us have been there done that more times than we wish we had to.

Ed  N1UR

[KB1SNJ]

Thank You

[N4UFO]

While it's not exactly filtering 60 Hz, there are ways to filter out 'line noise' which is likely what you are receiving...

https://www.universal-radio.com/catalog/filters/nir12.html

https://mfjenterprises.com/products/mfj-1026

I owned and used the first one years ago... and surprisingly, the worse the interference is, the better it works. Eventually the electric company fixed the problem that was on a nearby pole and I no longer needed to use the device. Which is what you might consider doing... tracking down the source of the noise and getting your power company to fix it. Because they likely WANT to... it is a loss of power and possible future failure for them. You can use a small portable AM radio to walk around and find it and if you get close enough, you might even be able to hear arcing from the pole with your ears.

73, Kevin N4UFO

[WA9AFM]

Is this radio an 'AC/DC' legacy radio?  Is so, try reversing the AC plug.  Also, 'pop the hood' and tap each of the tubes to see if any are 'microphonic', i.e. bad.

[KB1SNJ]

Thanks guys

It's an Arvin midget radio.  I just walked the area in front with a portable transistor and the power lines are emanating some noise for sure. Seems to fade a couple houses in both directions. About 100ft before my driveway is a transformer that is a peak, but my car radio really reacts just as I pull into my driveway. Walking back to my house it lowers that gets harsh at the outside of my house so there's probably a source there too. I cant power down right now but as soon as I can I will try to isolate that. I did call the power company several years ago and I got lucky, a knowledgeable guy showed up with a hi end sniffer and ordered a bunch of insulators changed up to 1/2 mile away. He also found a cable company device making a racket and informally called that in to them. We have a new power company now not sure what they would do but will ask.

Also, it's damp/wet today. I was told that makes a difference, if it happens hen wet thats one issue, when dry it's another (with power line insulators)

One other time it was a bad ballast on a mercury street light on the next street over. It was intermitent like every minute for 20 seconds then off again, and I got them to replace it. (Now we have new LED street lights.)

Because it can be like playing whackamole, I was hoping to just filter it out at the receiver. The MFJ would I'm sure work (I have a few of their stuff, never disappoints!) but I dont want to do that for every radio I have (I have a small collection).

It sounds like the line noise is mixing with the station freq I want to hear and cant be separated? What about a high quality magnetic loop antenna (like what I tried to build but a professionally made one)?

[WA3SKN]

You have a local noise source.  And the solution is to find and filter it.
It is probably being radiated via the power lines and incoming via your antenna.  The problem is that you share that transformer with several of your neighbors.  It could be a device in your house, but it could be in one (or more) of their houses.  Look for digital devices and poorly filtered wall wart type transformers... the usual culprits.

-Mike.

[KB1SNJ]

OK, this is interesting update to this problem. A few weeks ago, a bad wind storm was forecast for overnight. I suggested we sleep in our little camper in the front yard and "enjoy the storm" well at 5:30 am amidst the camper rocking and the wind howling, we were sleeping like babies and a loud crash woke me up (not her though). I popped open the door and there were tree branches everywhere, and our power line tangled in it. We lost our front yard tree and it ripped the power line down from the pole. The power company came out by late morning, and they reattached the line mid-span, (it was closer to the pole before, so they cut in new clean connections and shortened my power lines a bit) and the power was back on.

A day or so later, I noticed that I can actually listen to the little Arvin. Since the power line noise was variable before depending on the weather and temperature, I waited before believing this solved the jamming issue, but, it would seem that it has!

Must have been the power connection up at the pole was corroded or something and creating the RF noise (arcing?).


 

[W6QW]

There's some misconception here.  Power distribution lines do not cause interference in their natural state (no arcing, etc.) in your broadcast band Rx.  The only interference would be at 60Hz - think of the power transmission system as transmitter with a carrier frequency of 60 Hz.

If you are hearing the 'buzz' (commonly called arc-faulting) in you AM radio, that 'buzz' frequency is 120Hz as the arc fault will occur twice per 60Hz cycle.  If you have an oscilloscope, you can easily confirm this by measuring the period between the arc-faults (1/120 Hz = 8.34 mS) of the audio 'buzz' that you are observing. There can be multi-arc faults per cycle but the explanation is beyond the scope of this simple answer.

Lots of info on the web.  I also had a post a long while back in the eHam RFI forum on distinguishing common Rx RFI.  It includes pictures of RFI observations in a receiver.

Good hunting..

[KB1SNJ]

All I know is that the radio was useless then the horrendous buzzing stopped after they made a new connection at the street...

[AC2EU]

All I know is that the radio was useless then the horrendous buzzing stopped after they made a new connection at the street...

It could absolutely have been a corroded connection that was arcing. It will  generate all kinds of harmonics, modulated by 60 Hz. Sort of like an untuned spark gap transmitter!
If all is quiet now, perhaps that WAS the issue. If not, it's time to take another stroll with the transistor radio.

[KB1SNJ]

All I know is that the radio was useless then the horrendous buzzing stopped after they made a new connection at the street...

It could absolutely have been a corroded connection that was arcing. It will  generate all kinds of harmonics, modulated by 60 Hz. Sort of like an untuned spark gap transmitter!
If all is quiet now, perhaps that WAS the issue. If not, it's time to take another stroll with the transistor radio.

You know, about 5 years ago I called the power company to check out all the QRM around here (I live in dense suburban).  They sent a guy with a spectrum analyzer that he was not totally familiar with but he figured it out. He went a mile up and down the main road which has a quite high main "trunk" line, higher voltage than the neighborhood loop. He logged every bad insulator etc, and even found a cable internet unit spitting out noise, and called them as a courtesy. Two bucket trucks came out and they were way up changing insulators all day.  Things quieted down quite a bit. I cannot specifically recall but my local issue must have started after that. Whenever I pulled into my own driveway the AM radio in the car would hear it loud. That was right under this power line. I didnt think to call them again for some reason, just lived with it. In hindsight I should have!

By the way, I learned a tactic that can help find these power system sources, walk around with an AM radio, but when it gets loud, switch to a VHF handheld. The higher the frequency the more deaf the receiver will be to the source and can zero in on it that way.  You probably know this but someone reading this later may benefit.

[WB6BYU]

...By the way, I learned a tactic that can help find these power system sources, walk around with an AM radio, but when it gets loud, switch to a VHF handheld. The higher the frequency the more deaf the receiver will be to the source and can zero in on it that way.  You probably know this but someone reading this later may benefit.

Works best with a VHF receiver using AM mode.  That may
mean listening in the Aircraft band rather than on 2m.

But even with an FM receiver, you may get a meter indication,
in which case a small beam antenna can help pin it down even
faster.  It doesn't have to be very fancy to do the job.