Jeffdeham wrote:

I was looking at the rainbow tuner which matches a
half wave end fed antenna to 50 ohms using a quarter
wave radial. I am guessing it
works like a transformer but not sure. Here is
the schematic;

Ant |----- quarter wave radial
| |
| GND
----------
| )
--- )
Variable )----- 50 ohm
--- )
| )
| )
----------
|
GND


If it does work like a transformer how does it do it?
How is the matching done?

I'm not familiar with the rainbow tuner, but if I read your schematic right,
the tapped coil functions as an autotransformer. Autos are commonly used
as step-up and step-down transformers in power substations. A functional
equivalent using separate windings would look like this.


|
|
|
----------------
| )
| )
| )
----- )
----- ) ( ----------- 50 ohm
| ) (
| ) (
| ) (
-----------------------------------
|
GND




73 de KD5SZ