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"Buzz Saw" RFI Off And On, HF and VHF

Discussion in 'Ham Radio Discussions' started by K0DUC, Feb 26, 2021.

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  1. K0DUC

    K0DUC Ham Member QRZ Page

    Recently I've been having a problem in my shack with "buzz saw" RFI noises that seem to come and go, completely, from time to time, both on 11/10 meter and 2 meter.

    For example, a few days ago I heard some skip coming in on CB Channel 6, so I went to the main shack to give 10 meter SSB a try with my Yaesu 450. Couldn't make any contacts, but could hear plenty on parts of the band I don't have privileges on. Then I turned off the tuner and cruised 11 meter with the 450 to listen in and out of band, hearing endless amounts of Spanish in high quality in AM. All the while, noise ground floor was on the floor, did not even want to read on the S meter.

    Like other days and times, my CB/10 meter setup is very clean, I can take weak signal very well.

    Today I hear skip coming in, so I get down to the shack. Even make a contact with a fellow down in Arkansas on CB, short but very clean AM! Excited, I plug in the Yeasu 450 to do work on 10 meter SSB.... only to be greeted with a rhythmic, "buzz saw" RFI pulse, reading 3-4 S units! Disgusted and disappointed, I quit for dinner.

    I remember that this is the same exact "buzz saw" noise I get on 2 meter FM on weak signal. I started to get this a few weeks ago, and it is sometimes so bad I can't check into the local Canadian net across the border. On 2 meter, the noise is always there, but on the Yaesu 450 it seems to come and go.

    My Galaxy 2547 didn't suffer the same noise, plugged into the same tuner and feedline and antenna. Minutes before using the 450. The Galaxy isn't currently grounded.....

    Any help on this issue? Why would such RFI come and go on 10/11 meter? Is it a grounding issue, or ground loop of some sort? The appliances in the shack are few and always on. I've been thinking and looking and I'm stumped.

    Any help is appreciated.
     
  2. K1VSK

    K1VSK Ham Member QRZ Page

    First, check to see if it’s conducted or radiated noise which will eliminate many of the common sources.
     
  3. KC7JNJ

    KC7JNJ Ham Member QRZ Page

    If you can hear it on 2meter FM you can DF it. Check for if with a hand held and a beam. Then turn off power to everything in your house making sure it is not something in your house.
     
  4. KE0QQQ

    KE0QQQ XML Subscriber QRZ Page

    My guess is there is a trickle charger or something of the sort cycling on and off. I have to deal with the neighbor keeping the vette battery going all winter and the landscaper in back of me keeping his equipment charged up. I get 2 different varieties of buzzing myself.
    What cycles on and off in your world? Good luck,
     
  5. K0DUC

    K0DUC Ham Member QRZ Page

    Next door neighbor is half a mile away. So, all sources should be under my control. Main shop on the property is ~80 yards up the hill, main house is 100 yards up the hill from the cabin where I have my main radio setup.

    The trickle charger wasn't being used in the shop. Everything in the main house that was running when the "buzz saw" was on 10 meter was on when there is no "buzz saw" sound going. Currently the cabin with the radios has the same fridge, small electric oil radiator heater, a small digital clock, and a light or two on. The current power supply is a MFJ 4320 switcher, but why would that sometimes make noise on 10/11 meter and sometimes not? In any case, I'm going to replace it with an Astron 70, and it hasn't been done because I'm still figuring out where to put that gigantic chunk of heavy metal.

    That and the Galaxy 2547, which I currently just have plugged into the 120v and using its own power supply.... unless that's it? I would have thought it might have a quiet linear, but I'm not sure. Still, one would expect a radio made for 11 meter CB not to make noise on the very frequencies it operates on!

    I'll have to get a directional and see if I can't hunt it down. Tried it again this afternoon on the 450, and 10 meter was, again, about less than 1 S unit of noise.
     
  6. N0TZU

    N0TZU Platinum Subscriber Platinum Subscriber QRZ Page

    Let’s get specific. Come and go isnt very definitive.

    Is it rhythmic or regular, like some sort of device that is cycling on and off? Or is it random?

    Does day of week, or time of day, or weather affect it?

    Power pole problems can be more or less random, but dependent on weather.

    Cycling on and off is often an appliance, machine, or electrical equipment of some sort. Battery chargers are often noisy.

    Noise radiated by electrical devices can travel surprising distances because the power lines become antennas, and can also conduct the noise to your location.

    Good starting info here:

    http://www.arrl.org/radio-frequency-interference-rfi
     
    WQ4G likes this.
  7. N1YR

    N1YR Premium Subscriber QRZ Page

    One possibility: You have a fridge in the shack. We have a new refrigerator, one or two years old. It must be microprocessor controlled. It has three or four different audible noises it makes. As it cycles through its operating modes, it can jam up any AM radio placed anywhere near it. Older fridges just had a thermostatic control, which ran the compressor, or not.

    Don't forget to check LED fixtures or replacement bulbs with switch-mode current regulators. I also found one compact fluorescent bulb that was so noisy on RF that I had to mark it and hide it away for emergencies. But noise from lights wouldn't come and go like that from a fridge cycling would.
     
  8. K0DUC

    K0DUC Ham Member QRZ Page

    On 2 meter, it seems to be every Sunday evening, for the past three weeks, when I check into the local across the border net, whereas before I had perfectly clean (if weak signal) reception. Thus, I thought the "buzz saw" might be more to do with the Hayfield repeater up in Canada. I don't have the same problem on, say, the NOAA radio stations, even the weak far away ones. I don't get much 2 meter reception here because it is extremely depopulated and not much VHF action going on to test it against. I'm going to test out my reception on other repeaters this afternoon.

    The issue with 10/11 meter seems to just come and go. It is the same rhythmic "buzz saw", with the same frequency and sound when it does occur. For RFI, it is "clean" and has an extremely good rhythm. There is no other commonality, it can show up day or night, at any hour, regardless of what is being run in the shack. That's the head scratcher, it will show up to screw up my reception for a couple hours out of nowhere, then just go away back to nothing.

    The only things that have changed was reinstalling LMR 400 and repairing my MACO 5000 after a major windstorm months back, and I have also added grounding straps to my MFJ 12 volt power strip, as well as my MFJ 969 tuner. Which is why I wonder if my grounding might have caused some problem, even though it seems to be done correctly.

    Fridge is 30 years old, and I can hear it kick in and out, all you can tell is a small blip of static when it does. Very quiet. I've got a fluroescent bulb to light up where I operate! I'll try turning that off and on to see if that can trigger something, maybe the cold weather and the cold shack might be affecting it.
     
  9. W4IOA

    W4IOA Ham Member QRZ Page

    Well pumps can produce a lot of rfi. And they can screw up your radio from a good distance away.
     

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