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Noise on 40m - Intermittent

KF6JS Member ✭✭
edited January 2022 in Amateur Radio Interests
I've been chasing this 'broad noise' for awhile now - 40m is useless when it's on! When off, my noise floor is -120 - when on it goes to -85! It seems purely random - any time, day or night, various durations and periods in-between. See the pics: Noise off, Noise on and a chart of time and duration. If I remove the antenna, the noise is gone - noise floor goes to -120 with antenna #1 open or terminated with 50 ohms. Also, I have the same condition on antenna #2.

The equipment: 6600M (no GPS), internal antenna tuner, G5RVJR antenna at 30 feet.
Using Win 10 and Smart SDR or Maestro or remote access via iPad gives the same noise.

Question is...
Do you think this could be internal to the radio?
(although the antenna test suggests not)
Is there a radio clock or internal 'something' that could cause this?

Of course, I'll keep looking for stuff outside.....
(BTW - ALL internal home stuff has been eliminated - I just powered off the mains and the noise was still there with the 6600M on battery power)

Thanks fer any comments....KF6JS, Tony


  • Mike Steventon
    Mike Steventon Member ✭✭✭

    I get loads of “hash” very frequently on 40m band. It is definately not the radio (6600M here). I can verify this as I can quickly look at websdr HackGreen in the UK about 100 miles from me, and it show exactly the same results at exactly the same time. I have been told that it may be “over the horizon” radar, or other quite illegal activity. By the way, I have located other wipe-out hash that comes from the switch-mode psu charging a cordless vacuum cleaner in the house. It really aggravates me especially on 80m as it tries to top-up the charge every so often. Time to put it in the bin, I think!!

    Do you have a websdr reasonably close to you that you can check at the same time as the occurrences?

    Best of luck, amateur radio ain’t wot it used to be!!!!!

    73 Mike G4GWH.

  • Erika - KØDD
    Erika - KØDD Member ✭✭✭

    My neighbor has a big old plasma TV. It blitzes out 40m when it gets turned on. Lots of vertical lines across the screen. I have everything set to max fps and scan rates if I slowed it down it would look like you picture

  • Mike-VA3MW
    Mike-VA3MW Administrator, FlexRadio Employee, Community Manager, Super Elmer, Moderator admin


    Your test confirms that noise is external to the radio.

    Your first test is to figure out a way to run the radio on batteries and then turn off all your power if you can. See if the noise goes away. If it does, great that means it is your noise and likely solvable.

    The ARRL has good documentation on this:

    Mike va3mw

  • KF6JS
    KF6JS Member ✭✭
    MikeS....THANKS for the WebSDR idea - I forgot about that capability (it's 33 miles away).
    So this morning I checked both (WebSDR and my 6600M) and the noise is only on my Flex!
    SO Annoying!

    VA3MW - Yes, I put the 6600M on batteries and killed everything inside my home - even the battery powered PC! So I'm pretty sure it is not MY noise (I hope).
    I'll search the ARRL site too.
    (also, power-down on each breaker was for 5 min at least - assuring power drain on any devices!)

    I'll keep searching fer now!.....

    Thanks Again Everyone!
  • Mike Steventon
    Mike Steventon Member ✭✭✭

    Tony. Have you tried the other SCU as we both have two spectral capture units in the 6600M? You may possibly find a difference. I personally do not think you will, as I have great confidence in these radios. I have alway found the receive to be second-to none.

    I am actually toying with the idea of trying out an active magnetic loop receive antenna, which hopefully I can rotate to receive primarily the magnetic component of the signals that I want to hear and dismiss the electrical component as best as I can. I have read that they can be extremely effective as noise eliminators or at least noise reducers. DX Engineering do one, but it it frightfully expensive in the UK. I have some QRM on 40 due to broadband VDSL in my area, and I suspect that a mag-loop will be my answer to the maidens prayer. Maybe someone will read this who will either confirm my thoughts, or say it would be a waste of time and money. For the occasional annoyances, I guess you have used the exceptional TNF facility on the Flex. Highly effective at spot-frequencies.

    Good luck!

    73 Mike G4GWH

  • Patrick
    Patrick Member ✭✭✭

    Some thoughts on your problem. If it is randomly intermittent and does not have evenly spaces spikes. Then it could be a couple of things. Highest on my list is a power line related issue especially on the high voltage side of the system before the step down transformer. In this case it could be an insulator that is arcing due to build of materials from rain and wind. If humidity goes up these materials (salt) could conduct and cause broad band noise. The next possibility is, since you eliminated your own systems, is the possibility that in your neighborhood, there is some residents that have a malfunctioning device of some type. You may have to resort to using a portable RX to cruise the neighborhood to try and locate the source. If you do try to locate the source you may find one of the two possibilities. If it a power problem on a pole, call your power company and see if they will fix it. If it a residential problem, you may have talk to a resident, very tricky situation. My own experience I have had both resident and power company problems. The resident problem was solved when they moved (lucky me) but power company problem is still in progress. They opened a ticket for the LED street light that I located as the problem. Only time will tell, as this is the third time around with the power company. Next step report it to the FCC. I used to test electronics for Part 15 Compliant operation. I did test for radiated and conducted emissions and filed reports with the FCC. So good luck on your problem, it sometimes takes lots of patience and persistence to get these types of problems solved. Or it will never happen or will solve itself, which is maddening. ⚡️

  • WX7Y
    WX7Y Member ✭✭✭

    If in fact it is coming from a neighbors Plasma TV maybe it would be better all the way around maybe to offer to buy them a new Lower Priced same size HD LED TV for a few hundred bucks that doesn't have RFI issues.

    My Opinion which is not worth anything: The problem I dislike about the WEBSDR's is Operators audio out is NOT muted when they transmit and you hear the annoying echo.

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