+9 noise level 256 days a year. any help?

Discussion in 'General Technical Questions and Answers' started by N9ZDZ, Mar 30, 2019.

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  1. N0TZU

    N0TZU Platinum Subscriber Platinum Subscriber QRZ Page

    That seems to be a different noise than in the first few posts, is that correct? It sounds like RFI from some sort of equipment. Is it continuously across the band or is it many discrete frequencies across the band? Is it on other bands too?

    Was that in sideband? If so, please show us in AM mode.
     
  2. WN1MB

    WN1MB XML Subscriber QRZ Page

    Understood.

    Two sources could be in the same direction, too, yet if the offending frequencies are different, the device is only capable of tuning out one of them at a time. Therefore, it's better stated as a single source cancellation device; not single direction.
     
  3. N9ZDZ

    N9ZDZ Ham Member QRZ Page

    They just installed a new pole with new transformer and 2 new LED STREET LIGHTS 1 block away from my house I could handle the noise level before but now this is getting annoying . And yes its on AM also same noise . It lower on 40 meters but I can still tell its there same noise.
     
  4. VE3CLG

    VE3CLG Ham Member QRZ Page

    Yes i have read all , but that was just for fun.i know you are looking for help,but at the same time let put some smile in our face.Sorry if i make you feel bad .don't take it the wrong way.
    ve3clg
     
  5. W2WDX

    W2WDX Premium Subscriber QRZ Page

    This is clearly common-mode noise on the line and insufficient common point grounding. I assume the metal table is grounded by it touching or in contact with a concrete floor in the basement. I also assume you are depending solely on the AC safety ground and have no direct earth ground for the station.

    The thing you must do is get all your ground at the same potential. First you must have all you gear on a single point ground, preferably to a ground rod very close to the station. You also have to physically bond that station ground to your electrical safety ground rod. It all must be one electrode. That means physically bonding your AC electrical ground rod to your station ground rod.

    The voltages you are seeing on your meter are most likely common mode currents from man-made EMI from various sources around your home. This is evidenced also by seeing the same noise when using a battery. Since these currents have no direct path to ground, they remain and show up as a low AC potential on the coax, the AC grounds, wiring, chassis, etc and without a path to earth introduce noise into the receiver. The metal desk has a more direct path to earth and is at a lower potential than your station, ergo the AC voltage you measured. (I would bet if you took the probe you touched the desktop with and touched the concrete basement floor instead you would get nearly the same reading). Most times this EMI noise is very high on the 80M band due to the nature of the EMI commonly produced by electronics of various types being used today. The same noise may also be present on the AC safety ground lines in your house wiring since if you have no rods there is no physically short direct path to earth.

    You need to check several things. Is your AC panel in your home grounded? Do not rely on the "ground" coming from the power pole; it's too far away and may have significant noise itself, and may be at a different potential then earth nearby your station, like the concrete floor. The AC breaker panel itself must be grounded to a ground rod close to the panel. You also should have a ground bar behind your gear connected to a another ground rod near the station, with all the gear chassis connected to that bar. Then, (very important) the two ground rods must be physically bonded by a large wire to bring both rods to the same potential. Bear in mind, simply because the to rods are both in the dirt doesn't mean they will be at the same potential. You have to consider if not connected together by a wire, there will be a large resistor (the earth) between the two.

    I will bet if you get your grounding in order, a large percentage of the noise will drop out. Now ... that doesn't mean it will go away entirely since the same noise will be "received" by the antenna, especially on 80M. However, the voltage you have there is certainly going to show up at a higher level than the ambient noise received on the antenna.

    Back in the day this type of noise (both differential and common-mode) was less common since there was no digital anything, people had less electronics, and generally equipment was better shielded due to to the use of metal cabinets and such. The EMI was significantly lower or non-existent in some locales. These days EMI abounds.
     
    Last edited: Jul 23, 2019
    N9ZDZ and WN1MB like this.
  6. N9ZDZ

    N9ZDZ Ham Member QRZ Page

    I had CIPS come out and inspect there grounds and on my house they said everything was fine but I have also used a 4 foot ground rod and ran copper wire to it running from my radio to the out side rode and still no luck .CIPS is going to come bake out but we will see.
     
  7. N8FVJ

    N8FVJ Ham Member QRZ Page

    There is likely some nasty electronics trashing the bands in your neighborhood is my guess. I have some local electronics that trashes about 26 thru 30mHz with a 20 over S9 10 kHz wide signal every 50 kHz. It showed up two months ago. Other bands beyond 10 meters here is about S3 noise with 75 meters at night is about S5-S6.
     
  8. N9ZDZ

    N9ZDZ Ham Member QRZ Page

    This is what they installed 1 block over from my house.
    Image-178.jpg
     
  9. K7TRF

    K7TRF Premium Subscriber QRZ Page

    Get a handheld VHF airband receiver (they're cheap) and verify that excessive noise is coming from that pole or elsewhere. If you can pinpoint the noise source most utility companies will deal with it. If they won't check out the ARRL links on dealing with RFI and your options for getting it resolved.

    Those lights might be the source of the offending RFI but without actual receiver measurements to back that up no one will do anything about it. VHF am receivers are ideal for tracking down noise sources as the RFI tends to fall off fast at VHF frequencies so you have to get close to the source to identify it which helps when interference hunting.
     
  10. K7JOE

    K7JOE Ham Member QRZ Page

    I suspect this is switching power supply noise from a phone charger or similar - and is being picked up via the coax, ie, common mode noise coming in on the shield of the coax.

    Are you using a multiband antenna such as an OCF dipole? Or a Carolina (or any antenna whose name carries a 4-land or 5- land state in it, eg tennessee, or texas, or alabama) dipole or windom ? They are all are notorious for having common mode issues.

    If you have not done so yet, go buy two pieces of 240 torroid, mix 31, and place 8 to 10 loops of your coax through that donut. Install one just before the coax connects to the 75m antenna near the antenna feedpoint. Attach another one just before the coax enters the house, or right at the back of the radio. Palomar engineering sells them and I am a total believer. I bought lots of these and have fixed many antennas. They're about 10 each but they WORK to choke the common mode. Mix 31 operates from around 1 to 300 mhz or so.

    Dont buy from no-name ebay dealers. Get it direct from Palomar (*or Fair-Rite, the makers of the torroid material).

    I actually doubt it's the power transformer, nor the new LED lights. I bet it's something in a neighbors house that is causing your headache. One house over....not a city block away.... just my bet...

    I have a periodic transformer issue here - real bad in the cold and dry winter.. I get the snap crackle pop / arcing noise. Power company wont fix it... occasionally can be fixed temporarily by banging into the power pole slowly, just once, by rolling the truck and having the bumper "bump" the wooden pole.

    the grounding and bonding stuff, at this stage, is a total waste of your time...the signal is coming in on the antenna...grounding anything wont do a bit to eliminate the common mode.
     
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