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Re: [softrock40] external LPF

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  • Milt Cram
    ... Hi Ed, Simple answer--it would likely cause a problem. You should switch both the input and the output of the filters using a 2 pole 3 position switch. 73,
    Message 1 of 7 , Jan 16, 2013
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      On 1/16/2013 2:57 AM, edingraham wrote:
      > I was thinking about building an external 40M LPF in a box. Then I had the thought that I could also put an 80M LPF in the same box. Using a 3PST switch to select on one end: 40/80/bypass. But the other end would have both filters and bypass connected all the time.
      >
      > So my question is: if I select 40M, will having the 80M filter dangling by one end upset the impedance which the 40M load sees?
      >
      > 73, Ed WX4S
      Hi Ed,

      Simple answer--it would likely cause a problem.

      You should switch both the input and the output of the filters using a 2
      pole 3 position switch.

      73, Milt
      W8NUE
    • Alan
      ... Subject: Re: [softrock40] external LPF ... For years, as recommended by Tony we have been adding an extra, in series, external LPF to our Softrocks. Now we
      Message 2 of 7 , Jan 16, 2013
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        ----- Original Message -----
        Subject: Re: [softrock40] external LPF


        >
        > Simple answer--it would likely cause a problem.
        >
        > You should switch both the input and the output of the filters using a 2
        > pole 3 position switch.
        >

        For years, as recommended by Tony we have been adding an extra, in series, external LPF to our Softrocks.
        Now we are getting posts like this.
        Is this more theoretical?
        Does it really make very much difference?

        73 Alan G4ZFQ
      • Shirley Márquez Dúlcey
        If you re using a single band external filter you don t need any switches. That s probably the most common arrangement. If you DO switch the external filters,
        Message 3 of 7 , Jan 16, 2013
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          If you're using a single band external filter you don't need any switches. That's probably the most common arrangement.

          If you DO switch the external filters, you should use a 2 pole switch as K5BCQ suggests.
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