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10659Re: [loopantennas] A bit OT: new delay line kit

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  • Richard (Rick) Karlquist
    Jul 1, 2014
      On 7/1/2014 8:44 PM, 'pu3hag.l@...' pu3hag.l@...
      [loopantennas] wrote:
      > Hi,
      >
      > Chavdar Levkov, LZ1AQ - who runs active-antenna.eu
      > <http://active-antenna.eu> - has included a
      > 2nd kit to his site: delay lines for phases antenna array.
      >
      > I have one of his loop amplifiers still to build. I admit I have zero
      > knowledge on delay lines and need to research a bit on this topic.
      >
      > -- pu3hag huelbe
      >

      Well, research this:

      http://www.n6rk.com/Lumped_LC_Delay_Networks.gif

      I published this in 2008 and I see that LZ1AQ's delay
      lines are virtually identical to the ones I described.
      Maybe he reinvented this stuff. I have an unpublished
      PC board design that uses jumpers exactly like the LZ1AQ
      board. However, I learned the hard way not to try to
      use a binary series of delays. Unless the delays are
      exact, there will be gaps in coverage and the delay
      you happen to need might be unrealizable. Instead, what I
      do is to use a so-called "Radix 1.5" series with ratios
      of: 1, 1.5, 2.25, 3.375, etc. instead of 1, 2, 4, 8 etc.
      This has a substantial overlap and allows for fairly
      sloppy tolerances. I got this idea from the ADC designers
      at Agilent who used Radix 1.5 to eliminate missing codes.
      They said everyone in the ADC community knows about this.
      Except, the variable delay line is analogous to a DAC
      instead of an ADC. Some principle though.

      Rick
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