If my understanding is correct, the outside tube basically
creates the outside conductor of a coaxial section with the
Z averaged at 25 ohms at the mid way point, then tapering
down to zero Z at the far or "ground" end of the resistor.
In the design whereas a straight out tube is used its set
at a constant 25 ohm Z, which below about 50 MHz is
good enough, but for VHF/UHF loads the tapered design
is better.
I don't think Heath ever made the taper design in the
Cantenna, maybe it was modified by someone?
73, Mark WB8JKR
On Sun, 28 Dec 2003 09:57:15 -0800 skipp isaham <nospam4me@juno.com>
writes:
> I have a few Heathkit Cantenna Loads here. One has a
> tapered conductor as described below, others have a
> straight parallel pipe conductor. Does anyone know the
> history between the two types of conductors?
> skipp
>
> [paste]
> : From: R.Measures <r@somis.org>
> : To maintain constant Z with freq change,
> : a tapered conductor is placed parallel with the resistor
> : - with the widest spacing being at the coaxial RF
> : connector end.
>
>
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