In article ,
"Michael Lawson" wrote:

"starman" wrote in message
...
Pierre Vachon wrote:

Hi there, I am trying to build a longwire antenna for use in the
20 meter band to 70 meter band area. I was looking for advice on
what materials to use for the antenna and the lead in lines. I
will hook it up to a Drake r8B radio. What is the minimum height
it has to be? Where to groundit?.

Actually, does it have to be grounded if the radio is grounded at
the outlet?

I am a little limited in space as my yard is only 75 feet long
and there are power lines at the front. I assume that they are
the source of an irritating hum on the receiver on certain
frequencies.

Thanks for the help in advance.

Pierre

A real longwire antenna is much longer than what you are thinking
of building. The antenna you describe is called a 'random wire' or
inverted-L. This kind of antenna is not tuned for a specific band
or range of frequencies. In fact, it performs well throughout the
shortwave spectrum. See the following website for instructions on
building a good low noise inverted-L antenna. I use this kind with
my R8B.

http://www.anarc.org/naswa/badx/ante...e_antenna.html

Hmm. That brings up a question that I'd thought of earlier, but when
I was writing my posts, I forgot to put it in.

How do you figure out the impedance of various random wires of
different gauges?? John Doty's article mentioned an 18 gauge wire
hung more than a few feet above the ground, but I'm just curious what
sort of differences there would be using, say, 14, 16 or 22 gauge
wire in a similar scenario. I can't imagine trying to test it
without a load of some sort.

A decrease in the gauge number means an increase in the wire diameter.
If you increase the wire diameter the impedance goes down. If you place
the wire closer to the ground the impedance goes down.

The difference between a step in wire gauge is about 12 ohms.

A 16 gauge wire 5 to 15 feet off the ground ranges from 500 to 600
ohms.

--
Telamon
Ventura, California