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
K8GG replies:
If you are base or series feeding 128 ft of 45G tower, the approximate
impedance is 37 ohms over a good radial system.
One suggestion:
With 75 ohm hard line one can use a 2:1 UnUn to drop down to the antenna
impedance, or
2nd suggestion:
One can use a Pi-Network tuner or L-Net tuner at the antenna, or either
tuner at the shack as the SWR will be only about 2:1. There will be
essentially zero losses in hard line from your shack to the vertical
antenna. I would use the L-network at the shack, as it is easiest to adjust
if you have a good roller inductor and capacitor to build an L-net tuner, or
use the TenTec 229 or 238 tuners.
GL & 73, George K8GG
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