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TVI filter

Discussion in 'CB and Export Equipment and Accessories' started by codeman, Aug 27, 2017.

  1. codeman

    codeman Recovering Crackerhead

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    I live in a townhouse with a small patio where I have my antenna. Either a inverted v or a horizontal dipole made from two 4 foot fiberglass antennas. I use them at only about 10-12 feet high. Of course there are HOA restrictions here so I an trying to be stealthy as possible. I have had luck making contact both locally and dx with my setup. My one concern is interfering with my neighbor electronics. So far I haven't had any complaints and I don't want any.
    So what would be a good filter to help keep things clean? I have seen the RF LIMITED 3000 with mixed reviews, then I found an all in one tuner,swr/watt meter with a filter from rm Italy. I think it's called a HBF 500. Plus there is one from MFJ as well.
    Any thoughts on what would be a good deal for the money on one if these? Anyone use theses filters?


     
    #1 codeman, Aug 27, 2017
    Last edited: Aug 27, 2017
    Limeybastard likes this.

  2. sp5it

    sp5it Master of puppets

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    In 99% you would interfere with RF field, no filter can help.
    Mike
     
    Captain Kilowatt likes this.
  3. M0GVZ

    M0GVZ Sr. Member

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    A RF choke/balun at the antenna feed point. Most TVI/issues with things like burglar alarms is caused by the coax feeding the antenna radiating due to common mode RFI.
     
  4. fourstringburn

    fourstringburn W9WDX Amateur Radio Club Member K5KNM

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    That's your best bet is to stop it at the source as MOGVZ posted above.

    As for TVI filters,

    TVI filters were used for filtering out harmonics that would cause interference on your neighbor's TV. These days, Local broadcast TV is digital and has moved off VHF and is on UHF above 400 MHz so the 54 MHz harmonic frequency that was in line with 27 MHz isn't a problem anymore. Most people use Satellite or Cable TV as opposed to aerial antennas so I don't think TVI filters are necessary anymore although it couldn't hurt because I still have mine plugged in.

    Any TV interference these days would most likely be from feed line current radiation or some other flaw in your antenna system not from harmonic frequencies.
     
  5. codeman

    codeman Recovering Crackerhead

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    Ok. Thanks for the replies. My inverted v was bought with a balun, so it should be ok and that is the antenna I use 75 percent if the time at home. So with the horizontal dipole I should have a RF choke, right?

    I haven't noticed any interference with any of my own electronics so hopefully my neighbors aren't
    either.
     
  6. Limeybastard

    Limeybastard Active Member

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    My nightmare scenario is this..

    My neighbours hearing my voice thru their speakers :censored::cry:
     
    El Kabong likes this.
  7. Mustang 131

    Mustang 131 Sr. Member

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    1) Make a cheap choke at the input of your antenna (google it). A Low Pass will do almost nothing these days for TVI. Maybe help a bit with FM.
    2) Do not pinch your carrier...do not overmodulate. Stock new FCC radios work like magic.
    3) Grounding may help, it may hurt.
    4) Keep the Antenna as far as possible from electrical,cable and any houses. (i Know)
    5) For the love of god...use good coax and make sure your connections are solid
    6) Paint your antennas and coax for camouflage . Mixing Primer grays always seemed to work in Jersey.
    7) Sometimes you get a bad match...nothing will stop the interference.

    Good luck, I ran many in apartments with dipoles over the years with some luck. The biggest problem was all the RFI in MY receive on the HF band.
     
  8. fourstringburn

    fourstringburn W9WDX Amateur Radio Club Member K5KNM

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    That can be fixed as long as they are not amplified speakers such as a lot of home theatre speakers. Cheap computer speakers with inadequate shielding can get you a knock at the door also.

    Read what your fellow country man (MOGVZ) and Mustang 131 said about stopping it at the source first. Non-amplified speakers RFI can usually be cured by using Mix 31 or Mix 43 snap on ferrites with the excess speaker wire wrap around them such as in the pic below. Mix 31 is best for all the HF amateur frequencies while Mix 43 can work just as good above 20 MHz.


    [​IMG]
     
    Limeybastard likes this.
  9. Limeybastard

    Limeybastard Active Member

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    I luv you man, cheers. But does the wrapping of the speaker wire involve me going to my neighbors home and doing it for him or her? LOL
     
  10. fourstringburn

    fourstringburn W9WDX Amateur Radio Club Member K5KNM

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    Yes, No!

    Many of us keep a stock of ferrites on hand. I/2 inch ferrite beads are good for speaker wires.

    It's advisable that you at least provide them with some ferrites but show them how to use them. It's as simple as opening up the ferrite and wrapping the excess wire around the ferrite as close to the rear of the speaker itself, then snap it back shut. It's because of this excess wire that's commonplace with stereo speakers that acts as an antenna and can pickup RFI.

    It's best to be a good neighbor and do what's necessary to keep the peace while you enjoy your hobby.

    [​IMG]
     
    Limeybastard likes this.
  11. Captain Kilowatt

    Captain Kilowatt Professional Amateur
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    I would place it as close to the amp as you can. The problem is the speaker leads acting as an antenna and feeding the RF back into the amp where it is rectified and spit back out as audio. Placing them at the speaker end still allows the wire between the amp and speaker to feed that RF back into the amp. Placing them directly at the amp end chokes of any RF that the leads pick up and prevents it from getting back into the amp.
     
    bob85 likes this.
  12. Limeybastard

    Limeybastard Active Member

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    I think I am not getting my verbiage across correctly, I was stating my fear about my audio getting across my neighbors audio in a hyperhtecical
    Im totally with keeping good neighbors, but I didnt want to be in a situation where this occurs from the get go.

    Hence my first response of nightmares scenario of my neighbors hearing my voice in their speakers. LOL

    Im assuming those tvi filter boxes on eBay dont do much?
     
  13. fourstringburn

    fourstringburn W9WDX Amateur Radio Club Member K5KNM

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    Correct, as the name implies TVI filter means television interference filter. It filtered the harmonic frequencies of the CB band and others at 27 MHz for the old VHF TV frequencies starting at 54 Mhz.

    27 + 27 = 54

    See how that works to determine harmonic frequencies.
     
    Limeybastard likes this.
  14. fourstringburn

    fourstringburn W9WDX Amateur Radio Club Member K5KNM

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    True, but there are instances where RF comes through speakers even with the amp off.

    Then it would be wise to check if for RF with amp on or off to determine the best place for ferrites, maybe at both places.
     
  15. Captain Kilowatt

    Captain Kilowatt Professional Amateur
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    Only if the station is running REALLY high power. Speakers work on power and simply rectifying the RF of even moderately powered station will not produce enough drive to the speaker to be a problem. When RF is fed back into an amp it gets into the driver stage as well and comes out as many watts of audio.
     

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