Topband: Toploaded vertical - SWR

[Richard (Rick) Karlquist]

On 9/18/2018 4:19 PM, Joe Subich, W4TV wrote:
> 
> 2) use a 4:1 auto-transformer at the feed point - your antenna
>     analyzer says the real impedance is about 15 Ohms.  A 4:1
>     auto-transformer will get the SWR down to about 1.2:1.

Generally speaking, you will get a wider bandwidth with
a autotransformer than you will with an LC network.  To match
15 ohms to 50 ohms, you can wind 7 turns on a high-mu toroid and
drive the whole 7 turns from the radio.  The antenna is
tapped down to 4 turns.  7/4 squared is close to 50/15.
Less than 1.1:1 SWR.

BTW, an autotransformer automatically DC grounds the antenna.

Rick N6RK