RadioBanter - View Single Post - Even more on antenna feedlines and matching to an antenna.

December 5th 05, 04:25 AM posted to rec.radio.shortwave

In article . com,
wrote:

I've experimented with numerous low noise antenna receiving
configurations at this QTH and finally settled on a 90 foot "Windom"
configuration where the antenna is fed with 50 ohm coax at the 35%
length point with a 6:1 impedance transformer. The high-Z winding is 10
turns on a ferrite toroid and the coax is connected to 4 turns on the
toroid. There are no earth grounds and because of the separate windings
the antenna is galvanically isolated from the coax. The wire is
suspended about 6 inches above my west concrete wall which is about 5
feet high. This antenna has be the most effective antenna with minimal
noise for the 2 to 30 MHz bands.

As an example if your wire antenna is #18 wire about 10 feet off the
ground then the impedance of the wire is around 500 to 600 ohms. You
could probably use a higher ratio transformer like 11:1 instead of ~ 6:1.

I would use 13 turns to 4 turns instead of 10 to 4 turns.

--
Telamon
Ventura, California