Efficient RFI hunting tips?

Discussion in 'General Technical Questions and Answers' started by KC2VVJ, Feb 26, 2021.

ad: L-HROutlet
ad: l-rl
ad: Left-2
ad: abrind-2
ad: L-MFJ
ad: l-BCInc
ad: Subscribe
ad: l-gcopper
ad: Left-3
  1. KC2VVJ

    KC2VVJ Ham Member QRZ Page

    I've been riddled with S9+ noise floor on 80/40 and 10m no matter what time of day or night.

    I've looked through the various "how to find and deal with RFI", everything I see starts with a radio that has a Waterfall Display. I have an IC718 and it ain't got one. So, rather than scrolling till my finger is a nub, what's a simple and streamline method to find noise or find RFI without having waterfall to "get in the middle of it" and then go through breakers etc till it's gone and located at the source.
  2. WA7ARK

    WA7ARK Ham Member QRZ Page

    Last edited: Feb 26, 2021
    KC2VVJ, K0UO and N0TZU like this.
  3. G3YRO

    G3YRO Ham Member QRZ Page

    Step 1 is to run your receiver off a battery and eliminate EVERYTHING in your own house by turning the large Mains switch off.

    Once you have confirmed it's coming from another house, you need to locate it.

    Most radiated noise is worse on the lower bands . . . so simply using a small AM Radio (at the top end of the band) is usually pretty good at finding the source. The internal Ferrite Rod antenna is VERY directional . . . you get a big null off the ends, so use it to get a bearing on the noise source. Then move to a different place and get another bearing. Where the two lines cross is the location !

    (pretty obvious if it's a house down the street)

    Roger G3YRO
    KC2VVJ and K0UO like this.
  4. WA7ARK

    WA7ARK Ham Member QRZ Page

    The difference between trying to find multiple RFI sources using an AM radio tuned to a single frequency compared to being able to see 4 to 10MHz of spectrum all at once is like flying a Sopwith Camel vs flying an aircraft with a glass cockpit.
    KC2VVJ likes this.
  5. KX4OM

    KX4OM Ham Member QRZ Page

    "IMSAI Guy" on Youtube has a video on RFI-chasing with the Tiny-SA. He cobbled together a rig consisting of the SA and a camera on a stick of wood to be able to video his searches.

    I have used the Northern Utah WebSDR, a lot. Nice break from watching CNN :)

    Ted, KX4OM
    KC2VVJ likes this.
  6. WA7ARK

    WA7ARK Ham Member QRZ Page

    I have a regular 40m group that meets weekly where the ~10 participants are all over the Western US. Invariably, someone is too close (like from here to Tuscon or from here to LA) and I cannot receive them at that time of morning. Using the N.Ut or the KFS webSDRs solves that problem 'cause it is far enough from both of us. Clint is a member of our 40m group...
    KC2VVJ, KX4OM and K0UO like this.
  7. K3RU

    K3RU Ham Member QRZ Page

    Read my previous posts especially the most recent one (several days ago) regarding chasing down noise.
    My older posts most all deal with my own RFI adventures and how I dealt with them. You may or may not find any useful to you information but at least you will read exactly how I successfully dealt with some serious RFI.

    Depending on how you choose to approach the RFI problem, the better equipped you are, the easier it is.

    "Efficient" is a good way to put it, I never thought of it that way.
    KC2VVJ likes this.
  8. K1LKP

    K1LKP Platinum Subscriber Platinum Subscriber QRZ Page

  9. N3PM

    N3PM Ham Member QRZ Page

    I used a baby monitor when I was checking around the property. It let me hear the radio without running back and forth.
    Mike N3PM
    KC2VVJ likes this.
  10. G0OIL

    G0OIL Ham Member QRZ Page

    I've managed to find plenty of RFI just using a portable radio (an old Sony ICF7600) and walking around the neighbourhood. It's not great but has helped me to find a lot of the worst noise caused by cruddy Switched Mode Power supplies.

    There's a good article in the March 2021 QST by WD8DSB regarding directional DF antennas, though I have found that tuned shielded loops work well to get a few bearings on the noise. He also has Youtube videos and links to small loops that work on the higher bands. wd8dsb - YouTube

    I have also used a "Malahit" SDR bought on ebay. these are Chinese copies of the Russian original. I did approach the original designer to see if they could supply one but got no response to took a chance on a Chinese one. They are about £160 for the registered 5-KHz-2GHz one. The 200MHz ones are "trial" software that's not very good. They aren't a perfect copy since there are a few birdies that you have to be careful not to mistake for QRM but they fit in the palm of your hand and have a waterfall display, S meter and audio, so couple that to a loop and you're in business.

    Here's another link to a small tuned loop Small Tuned DF Loop (google.com)
    Note the twisted pair of wires from the pickup loop to the RX! Remember to do that (and stick a few turns through a ferrite ring) or you'll screw up the directivity. Putting a shield over those wires may help more so that it doesn't couple to your body - after all the human body is a 6ft high bag of salt water so does have an effect on 28MHz and above

Share This Page