Noise floor on HF increases at night

Discussion in 'Antennas, Feedlines, Towers & Rotors' started by KE0STP, Sep 16, 2020.

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  1. KE0STP

    KE0STP Ham Member QRZ Page

    I have a My Antennas EFHW-4010 mounted about 25 feet above the ground on an aluminum mast strung to a tripod across the top of my house that is on my garage.

    I am using an ICOM 7100, and the system is grounded to an 8 foot copper ground rod driven into the dirt.

    My problem is that the noise floor on HF during the day ranges from 3 to 5, but when the sun goes down it goes up to 9 and I find it unusable. I live in a rural area not near any high powerlines so don’t know of any outside interference caused by my location.

    I was speaking to another operator locally today who happens to have the same antenna and he has exactly the same experience.

    Is this an inherent issue with end fed antennas or is there something I can do to improve this?

    I emailed My Antennas today, and their response was: “You have classic home-generated noise... if noise increases at night, you need to find the source by switcj=hing breakers in your home... but it could come from far away. The antenna has nothing to do with generating or being prone to noise at night vs
    Further, the noise floor is different from band to the band too... as well as ionosphere changes.

    So, if I have “home generated noise”, and it might not even be from my home, how can I filter it out?
     
  2. NG1H

    NG1H XML Subscriber QRZ Page

    Your house: Run the radio from a battery and turn off all breakers. If noise stops turn them on one by one until the noise starts.

    Someone else' house: You don't to build something this fancy but it will give you some ideas http://www.arrl.org/files/file/RFI/Thompson Noise.pdf
     
    K7JOE and AK5B like this.
  3. N0TZU

    N0TZU Platinum Subscriber Platinum Subscriber QRZ Page

    What band is this on? Lower bands can become more noisy at night when the ionosphere losses are reduced and noise can be heard from far away.
     
    PU2OZT and AG5CK like this.
  4. KE0STP

    KE0STP Ham Member QRZ Page

    20 and 40
     
  5. KE0STP

    KE0STP Ham Member QRZ Page

    Now that I think about it some more, I do have a next-door neighbor with a street light in their yard. I suppose I can watch the s-meter when the light comes on and see if that is it. If it is, then what?
     
    WA8FOZ, AK5B, PU2OZT and 1 other person like this.
  6. W0XA

    W0XA XML Subscriber QRZ Page

    Do you have your coax shield grounded before it comes in the house?
    I had a lot of noise on my efhw and once I grounded all coax at a newly installed grounded panel it all went away.
     
  7. KB1CKT

    KB1CKT Ham Member QRZ Page

    If it is the street light you can complain to the power company about it (? think they own it). If it's a neighbor's light then a visit with a six pack might be in order, along with a good explanation as to why you want to check out the light that they have.

    Lots of places for noise to be generated. Any chance you can get the antenna away from the house? Even just temporarily up on some poles, just to get some distance.
     
  8. KA0HCP

    KA0HCP XML Subscriber QRZ Page

  9. W7UUU

    W7UUU Super Moderator Lifetime Member 133 Administrator Volunteer Moderator Platinum Subscriber Life Member QRZ Page

    Until you rule out your own house, you'll be chasing your tail.

    As suggested above, power your radio from a 12v battery (obviously on "receive" only!) and turn off all of your circuit breakers.

    If the noise stops or reduces dramatically, the problem is in YOUR house. If there's no change, then it's time to start looking into what the neighbors might be up to. If the noise DOES drop, turn on one breaker at a time until it returns then figure out what's plugged into that breaker.

    You would be utterly surprised at what a 2 ounce tiny Chinese wall wart can do!!! I have personal experience with such a wall wart causing S9+10 noise on 80/40 - until I did the "turn off all the breakers" test I would likely never have found it. And don't assume that just because you find one noisy device that there are no more! When I did my big "noise search" 2 years ago, it turned out that 4 "cheap Chinese wall warts" were all contributing

    Dave
    W7UUU
     
    PU2OZT, K7JOE, W9FL and 4 others like this.
  10. WA7ARK

    WA7ARK Ham Member QRZ Page

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