Topband: New install being put together

[Kenneth Silverman]

Brian Gieryk wrote:
> Good morning all!
>
> I am in the process of building a "new" 160 station.
>
> The object is:
>
> 128' base insulated tower (located, I think)
> 1 kW Bauer 707 TX
> 7/8" rigid transmission line
>
> What I need is guidance in the design of an AM broadcast style ATU for
> the tower base.
>
> TNX in advance!
>
> Brian
> KE6IYC

When you have a low impedance antenna (in this case ~35 ohms) going to a
higher impedance feed line (either 50 or 75 ohms), I would use a hairpin
coil across the feed point rather than a tuner at the base.  This assumes
the vertical is resonated at the desired frequency.  This is much simpler
than a tuner or L network at the base, and provides a DC shunt to ground.  I
would think a few turns of 2-3" diameter coil would do the trick.

If the vertical is not resonated, then the tuner approach would provide you
with both the correct impedance and VSWR match.

Kenny K2KW