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11 meter bandpass filter

Discussion in 'CB and Export Equipment and Accessories' started by 86lidewell, Apr 25, 2021.

  1. sp5it

    sp5it Master of puppets

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    According to this image this filter is crap.
    Look at popular Bencher YA-1.
    [​IMG]
    So, for 1st harmonic attenuation YA-1 is light years ahead. Checkmate.
    IMG_0055.JPG


     
    #16 sp5it, Apr 26, 2021
    Last edited: Apr 26, 2021
    Slowmover likes this.

  2. sp5it

    sp5it Master of puppets

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    You use bandpass filters to be able to transmit and receive on different bands at the same time. For example: you have 2 radios. 10 and 11m. When you transmit on one of them, the other is deaf because of the other transmitting. With bandpass filters you can use them both at the same time.
    For harmonics get quality low pass filter, it will do the job.
    Mike
     
  3. jkp1

    jkp1 Active Member

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    Ok. Thanks. I thought a band pass filter would be good to keep out everything that wasn't 11m with the hope of making 11m quieter. I guess my ignorance is showing.
     
    Slowmover likes this.
  4. Slowmover

    Slowmover Elmer

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    See screenshot from other thread. “Attenuating Harmonics”, isn’t the same question. (Use of a Low Pass Filter).

    Bandpass Filters are used in Contesting to avoid interference with others on adjacent bands (and vice-versa).

    .

    .
     
    Eldorado828, 86lidewell and sp5it like this.
  5. Slowmover

    Slowmover Elmer

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    CB Radio had a reputation of causing interference with close-by television station reception. A reputation that lingered after radio circuitry additions and changes after the 1960s. A Low Pass Filter was used to avoid interference from HF to VHF & UHF.

    TV “gone digital” removed the affected portion of radio spectrum to ones higher. To the point most LPF manufacturers no longer offer these devices (see used market).

    I’d have one in a mobile (assuming it checked out for operation; wasn’t damaged), except that physical size means a more difficult installation.

    The quite-small BP filter I’m using makes no manufacturers claim to harmonics attenuation. It has worked so far as I’m concerned in cleaning up what the transceiver has to deal with (amateur gear has far more “ability” built-in to filter signal).

    Between the DSP filter and the BP filter, the former is an outstanding success in this experiment of trying some amateur gear with CB radios. The BP, less so. A marginal versus MAJOR addition.

    The amp brand I’ve been using claims LP attenuation, but I’ve not had that tested. The RM ITALY 27/586 LPF “may” be the same circuitry, and when available is about $45.00.

    .
     
    #20 Slowmover, Apr 26, 2021
    Last edited: Apr 26, 2021
  6. 86lidewell

    86lidewell Active Member

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    I can confirm the RM Italy LPF does filter out the 54Mhz harmonic.
     
  7. 86lidewell

    86lidewell Active Member

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    tried this 27mHz band filter out just now between the radio and the amp. SWR is now bad on the radio side and the antenna side with <10w input.

    The low pass filter on the radio side fixed the radio-to-amp SWR, (SWR with or without LPF is always fine on antenna side) but this thing ruins both radio and antenna sides. :(

    more noodlin on this is required....
     
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  8. Slowmover

    Slowmover Elmer

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    Ran the provided exterior studs with woven, braided strap to ground?

    .
     
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  9. 86lidewell

    86lidewell Active Member

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    nope. will try that. Thanks.
     

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