[Antennas] DCTL Antenna Question

Sat, 28 Feb 2004 03:59:25 +0000

Terry.
   Thanks for the understanding and the reply. I do not use an antenna  
matching unit with my "minimmalist" 100mw Qrp rigs on 30 & 40m (really only 
40 right now, until I aquire another "Altoids" tin, Hi, Hi)

The reason I want to go to 450 ladder line is 6:1 baluns are a bitch and 9:1 
is a "piece of cake!"

  "Communications" is a People skill, the rest is technology.
             Durwydd MacTara

>From: Terry Conboy <[email protected]>
>To: [email protected]
>Subject: Re: [Antennas] DCTL Antenna Question
>Date: Fri, 27 Feb 2004 19:15:17 -0800
>
>At 04:28 PM 2004-02-27, Durwydd MacTara wrote:
>>Why? Since the Velocity factor and capacitances are different for the two 
>>feedlines, I figured the formulae would also differ, especially for a 
>>resonant antenna...
>
>Harvey, have you (or WA6QBU or others) built a DCTL using 450 ohm line for 
>the antenna portion?  Since this antenna is a capacitively loaded 
>quarter-wavelength dipole wrapped into a loop (with added capacitive 
>end-to-end loading), I'd also expect that having a different capacitance 
>per foot with 450 line might have some effect on the resonance.
>
>The antenna and the open stub capacitance will be about 24% less for the 
>same physical lengths (assuming 300 ohm VF=0.8 and 450 ohm VF=0.91).  Also, 
>the shorted stub will probably have about 32% higher inductance using a 450 
>ohm line with the same physical length.
>
>For certain, the SWR on the feedline isn't too important, but it might 
>affect the ability to match the line if the antenna matching unit has a 
>limited range (such as the built-in tuners in many transceivers).
>
>73, Terry
>
>
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