Topband: Ladder line + tuner

[Wes Stewart]

I second TLDetails.  TLW, not so much.

On 11/20/2016 6:13 PM, Paul Christensen wrote:
> David,
>
> I think the best and quickest way to understand and observe line impedance
> transformations is to model it using software.  Two popular programs are TLW
> and TLDetails.  TLW is bundled with the ARRL Antenna Book.  TLDetails can be
> downloaded here:
>
> http://www.ac6la.com/tldetails1.html
>
> It won't take you long to perform several "what if" impedance
> transformations by varying line length and type.
>
> Paul, W9AC
>
> -----Original Message-----
> From: Topband [mailto:topband-bounces at contesting.com] On Behalf Of D Rodman
> MD
> Sent: Sunday, November 20, 2016 8:01 PM
> To: topband at contesting.com
> Subject: Topband: Ladder line + tuner
>
> I designed a loop for 100 ohm impedance and fed with coax and 1/4 wave
> transformer.  It has worked well for years.  I got the bright idea to
> replace the coaxial feed with 35' of 450 ohm ladder line and a Bliss remote
> tuner.  This combination would not match.  I experimented.  A nice dip in
> VSWR was noted about 400kHz lower than the bottom of the band where that
> combination of antenna plus ladder line was almost perfectly resonant.  A
> versa tuner WOULD tune it but I needed to add about 90' of ladder line for
> the remote tuner to produce a reasonable lower complex impedance inside the
> band (actually it was reduced to about 58 + j6).  The impedance with 35' of
> line was over 1K and this is too large of a value for that tuner to accept.
> (That is a previously made tuner with vacuum capacitor and large roller
> inductor.)  Does anyone have knowledge or experience with impedance
> transformation on ladder lines that might be able to teach me something here
> about the effects I noted???  Thanks.
>
> --
> David J Rodman MD
> Assistant Clinical Professor
> Department of Ophthalmology
> SUNY/Buffalo
>
> Office 716-857-8654
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