RadioBanter - View Single Post - A short 160M antenna

John S · November 8th 14, 05:22 PM posted to rec.radio.amateur.antenna

On 11/8/2014 10:45 AM, wrote:
John S wrote:
On 11/7/2014 12:58 PM, wrote:
wrote:

snip

The only downside to this antenna is that it is extremely narrow
banded, only about a kHz or so.

snip

I realized I should expand on that.

With all 5 inductors the same value the 5:1 bandwidth is about 500 Hz.

By staggering the values of the inductors in the four legs the bandwidth
can be improved by a little bit.

The best I could accomplish was about 1 Khz by making the leg values
.96, .98, 1.02, and 1.04 times the central leg value.

Going beyond a step factor of .02 made little difference in the bandwidth
and the resonant frequency SWR started to increase.

Okay, but the starting target was to be able to feed a short antenna
with good efficiency and I think you hit that target. I know you want to
keep it as practical as possible, but I am impressed with your results.

Thanks.

The whole point of the exercise was to show there are way to overcome
the generally low impedance of short antennas.

Exactly! It was a challenge which has been shown to be surmountable by
design. Feed losses become less of a burden this way.

Do you think your results could be practical? Could ground resistance be
used to widen the BW? I know, there are losses. But, maybe worth it?

What do you think?