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Antenna ground and noise on HF????? Calling all Elmers

Discussion in 'Ham Equipment' started by archjeb, Nov 30, 2018.

  1. archjeb

    archjeb Member

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    Folks,

    I'm scratching my head here and maybe you can help me out.

    I noticed today that I dropped by noise by at least S3 on the meter for 80/40meters by disconnecting the other 2 radios (VHF & UHF) that are connected to the same face plate/cover plate on the wall. See the attached picture. Its a stainless cover plate, and I drilled 3 holes and mounted the bulk head connectors to this so I had a clean demarcation point from the outside runs to my inside short connections to my radios.

    But what is really strange is that if I disconnected two of my connections and just leave the HF radio connected, I get a drop in my noise by at least 3 s units. Disconnecting the power on the other radios made no change...its just the antennas or probably the coax shields.

    Outside the house, each of those bulkhead connectors are bonded to a ground plate with lightening arrestors which is also fed with a #8 ground to a ground rod.

    Any thoughts on this?



    Should my face plate on the interior wall be a plastic one so that the antenna shields are not bonded among the 3 radios? Any suggestions?
    Antenna-connections.jpg

    Thanks,

    -J
     

  2. 338_MtRushmore

    338_MtRushmore Well-Known Member

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    I'm no elmer, but I think that stainless plate is unnecessary. You should have 1 ground, but having your coax bonded before the actual ground could be bad? Are there any other possible ground loops in the system?
     
  3. archjeb

    archjeb Member

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    I would think that the stainless steel cover plate is possibly creating a ground loop as we're bonded there...and then outside on the actual ground plate.

    Tomorrow, I'll dismantle the cover plate and test again to see if it makes a difference.

    -J
     
  4. Tallman

    Tallman W9WDX Amateur Radio Member, KW4YJ EXTRA class

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    If your station grounds don't look like this diagram below, you have work to do. Do not solder any of these connections. They need to be hard clamped because if you actually get hit by lightning the solder will melt and leave you unprotected. If you still have a noise problem run your radio gear on a battery and switch off your breakers one by one and see if the noise goes away. If it does the noise is in your house. If it does not the noise is outside of your house. Power lines, transformers, burglar alarms, flat screen tv's and such make their own noises.


    [​IMG]
     
    #4 Tallman, Nov 30, 2018
    Last edited: Nov 30, 2018
  5. 338_MtRushmore

    338_MtRushmore Well-Known Member

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    Biggest thing I usually see is failure to isolate the ground on equipment AC plugs. AC plug grounds + station ground = major ground loops.
     
    BenMara likes this.
  6. loosecannon

    loosecannon Sr. Member

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    what kind of HF antenna are you using?
    how is it fed?
    LC
     
  7. Robb

    Robb Yup

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    Cell phone chargers, LCD screens (TV or computer), computer noise (common cause), and many other cheap Chinese electronic gear are not built with quiet RF in mind; they are built to make it to market and be the cheapest price to get the greatest amount of sales. No other provisions are made. RF issues? You are on your own, jack. Just disconnect them one at a time and then listen to the noise melt away.
     
  8. Handy Andy

    Handy Andy Do Your Research First, Then Decide...

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    The "ground loop" issue is quite common. Both on the wall plate inside and the outer wall standoff - which means the coax to these 3 separate connections - if it is a specific length - then you have a pickup of common mode currents in the wall as well as your breakpoint inside - it may be done too well. The internal coax within the wall can be doing this.

    Ok, you get this noise on 40 M - which is about 7MHz - lots of stuff pokes along at 7 MHz even onboard CPU clocks that keep memory and time alive. Bit that is very remote - but you do tell us that this problem disappears when they are unplugged from that wall - so the common point - is that stainless steel wall plate that allow all the shield grounds to tie to a common point not only in the home but externally too.

    You can verify by leaving all 3 in, you get your noise factor -then go outside and disconnect the ones for your VHF and UHF connections - if the problem persists - it's the wall plate, if it goes away, make a choice on which has to stay...and run grounds to EACH separately not bonded in two places...

    Added...

    My personal choice, knowing what lightning can do to a home even from a strike blocks away, your' better off leaving the bonded ground outside - and use a PLASTIC wall plate to isolate any hazardous voltages from ground currents rising faster then when you can hear the arrestors outside snapping away trying to drain off the charge thru a spark gap...in your radios' receiver
     
    #8 Handy Andy, Nov 30, 2018
    Last edited: Nov 30, 2018
  9. archjeb

    archjeb Member

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    So, I got some significant improvement today.

    I'm using Anderson Pole connectors and a multi-pole junction to feed the 3 radios off the same power feed. I don't run TX on all 3 radios at the same time, so we never overload the power.
    At any rate, the HF radio I had 2 toroid chokes wound on the power feed - a type 31 and a type 43 mix. But...on the VHF and UHF radios, I had nothing. So I went ahead and added two toroid chokes on the VHF and UHF radio. Believe it or not, that dropped by noise by 2 S units on my HF radio.

    At the feedpoint of my vertical HF antenna, I had about 10 turns of coax coiled up. I went ahead and grabbed a type 31 and type 43 toroid and used about 10 turns through those and my noise dropped another 2 S units.

    So now my noise floor is a lot better at 40m. At 160m its pretty darn quite now - I mean a BIG difference.

    80m, is still pretty noisy. I have a lot of hash noise that is coming from stuff radiating from the house. If I kill the power to the house, most of that hash noise drops.

    So I went ahead and put everything back on the stainless face plate /w bulk head connectors as it looks like I'm not getting the same issue now after I put all the toroid chokes in. I assume its masking or filtering whatever common mode noise was coming across the coax shields.

    Now to figure out where all the hash is coming from on 80meters. I have about 3 S units of constant hash. If I shut off the service mains and run on battery power, I have no S units of noise. The noise might be coming from utility power though. I'll have to test per circuit to see if the source is me or if its utility feed. I notice in my mobile HF rig, I'm getting the same hash if I'm close to the house.

    At any rate, amazing what those mix 31 and mix 43 toriod chokes make....

    -J
     
  10. Road Squawker

    Road Squawker Sr. Member

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    The first thing to do is to determine if the hash is on your power wiring or if it is being received from an outside source.

    simply disconnecting all antennas will determine that.
     
  11. oldtymer

    oldtymer Member

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    You should use a separate ground for your HF radio as Tallman showed in the above
    post you are creating a ground loop.
    Also may sound dumb to a lot of people but the composition of your soil can affect how
    well you are grounded.
    Use a good copper UL ground rod. Buy it at a electrical supply house not the crap
    Lowes & Home Depot sell.
    Now here is where some people will think I am nuts but I take a 5 gallon bucket & put
    a shovel of rock salt & fill it with hot water, let it dissolve & pour it around your ground rod(s). I also do the same for the ground rods on my tower, each leg has its own rod.
    I do this every three months & it made a big difference in my noise here.
     
    #11 oldtymer, Nov 30, 2018
    Last edited: Dec 1, 2018
    BenMara and Tallman like this.
  12. loosecannon

    loosecannon Sr. Member

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    isn't 80 meters inherently noisy?
    LC
     
  13. Tallman

    Tallman W9WDX Amateur Radio Member, KW4YJ EXTRA class

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    I did that when lived in Texas. It does work!
     
  14. archjeb

    archjeb Member

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    Disconnecting my antennas and I have NO NOISE at all.

    But the noise is indeed traveling through the house wiring because when I shut the mains off I have no noise.
    I run my rig off an AGM battery that uses a West Mountain Radio PWRgate to charge it...thus able to run completely on battery power.
     
  15. Handy Andy

    Handy Andy Do Your Research First, Then Decide...

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    Did that also for my service mains entrance - only once a year in winter to help with soil conductivity around the ground rod at the service entrance...
     

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