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Re: [loopantennas] Fewer turns in loop

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  • toddroberts2001@aol.com
    In a message dated 6/30/2006 10:51:51 AM Eastern Standard Time, craig@littleriverphotography.com writes: Since I only want to tune the upper portion of the
    Message 1 of 6 , Jun 30, 2006
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      In a message dated 6/30/2006 10:51:51 AM Eastern Standard Time,
      craig@... writes:
      Since I only want to tune the upper
      portion of the band, should I use fewer turns of wire and more
      capacitance to achieve resonance at the selected frequency? If Q is
      affected by the resistance of the wire in the loop, shouldn't fewer
      turns result in higher Q?

      Q is just one factor of a loop antenna. All else being equal I think more
      turns on a loop provides more signal voltage for the same size antenna versus
      fewer turns. Higher Q is not always wanted in a loop used for broadcast band
      listening. If the Q is too high the tuning becomes critical and the bandwidth
      will be narrow cutting off the higher audio frequencies leaving broadcast audio
      sounding muffled and bassy. A number of high-performance loop antennas have a
      switchable Q-killer built in for this reason. 73 Todd WD4NGG
    • Erle Carey
      I m not a electrical genius but it seem sto me that you should optimize for a center frequency and use a standard 365pf capacitor. If you have time to
      Message 2 of 6 , Jul 14, 2006
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        I'm not a electrical genius but it seem sto me that you should
        optimize for a center frequency and use a standard 365pf capacitor. If
        you have time to experiment by all means do so.. Start with more turns
        and work your way down. There is no way to know the Q of the antenna
        unless unless you have the test equipment. I got a post in my email
        today asking about the dimensions for a 433Mhz loop. It qould be tiny
        and what is up around that frequency?



        --- In loopantennas@yahoogroups.com, "Craig Cochran" <craig@...> wrote:
        >
        > I wrote in a previous post that I wanted to make a dedicated loop to
        > receive one of my favorite stations on 1450 kHz.
        > Since I want my system Q to be as high as possible, would it be better
        > for me to use FEWER turns in my coil of wire and a larger capacitor
        > than usual?
        >
        > In a 3 foot diameter loop that would tune the entire BCB I guess I
        > would use approximately 8 turns of wire (the exact numbers are not
        > important for my discussion). I would guess about 30-50 pf of the
        > variable capacitor would be used. Since I only want to tune the upper
        > portion of the band, should I use fewer turns of wire and more
        > capacitance to achieve resonance at the selected frequency? If Q is
        > affected by the resistance of the wire in the loop, shouldn't fewer
        > turns result in higher Q?
        >
        > What would be the minimum number of turns I could use to maximise Q? Is
        > there a resonable limit to the size of capacitor(s) I might use?
        >
        > Could someone enlighten my on this issue.
        >
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