In article . com,
"RHF" wrote:

Snip

= = = In ,
= = = "Jack Painter" 223bthp@c... wrote:

C.E.,

I didn't mean to imply that an HF antenna would normally
transmit farther than it can receive, only that a random
wire can sometimes outperform it on the receive-end.

This can happen even when listening on the transmitting
antenna's resonant frequency.

Snip

Highly unlikely on receive for the same reason as on transmit.

--
Telamon
Ventura, California

Highly unlikely on receive for the same reason as on transmit.
--
Telamon
Ventura, California

I agree in general, except for the fact that a dipole has a
characteristic directionality, whereas a random wire significantly
shorter than the wavelength will be omnidirectional. I suspect that
there will be occasional times when this factor matters.

When it doesn't matter, a random wire is still a more versatile antenna
than a single-lambda dipole, even when untuned.

I have an Alpha-Delta DXUltra, which is basically a multi-lambda
dipole, and a 60-foot random wire through a transformer at 20 feet
elevation above ground. Noise levels aside, there is little I can hear
on the DXUltra that doesn't appear on the wire, and quite a bit on the
wire, especially at freqs 6 MHz, that is inaudible on the DXUltra
(even though the DXUltra supposedly is good down to 120 meters - this
loss of signal may be a function of inadequate height, since the
antenna center is only 27 feet sloping to 7 feet at either end).

Bruce Jensen

On 8 Sep 2005 08:17:00 -0700, "bpnjensen" wrote:

I agree in general, except for the fact that a dipole has a
characteristic directionality, whereas a random wire significantly
shorter than the wavelength will be omnidirectional. I suspect that
there will be occasional times when this factor matters.

When it doesn't matter, a random wire is still a more versatile antenna
than a single-lambda dipole, even when untuned.

I have an Alpha-Delta DXUltra, which is basically a multi-lambda
dipole, and a 60-foot random wire through a transformer at 20 feet
elevation above ground. Noise levels aside, there is little I can hear
on the DXUltra that doesn't appear on the wire, and quite a bit on the
wire, especially at freqs 6 MHz, that is inaudible on the DXUltra
(even though the DXUltra supposedly is good down to 120 meters - this
loss of signal may be a function of inadequate height, since the
antenna center is only 27 feet sloping to 7 feet at either end).

Bruce Jensen

I find a random wire superior overall to just about any ''tailor
made'' SWL antenna I've tried.

I find a random wire superior overall to just about any ''tailor
made'' SWL antenna I've tried.

I do find that the dipole is wonderful on 7 MHz, and 11 MHz and up. On
9 and 6 it's about a toss-up, and on down through the tropicals the
wire is better.

My big problem is noise, especially on the lower bands. I have an MFJ
noise cancelling unit that works with the two antennas, but I think two
simpel wires phased would work rather better. If I can arrange such an
array that can be set up on my smallish property, I will let folks
know. Meanwhile, I still have a large horizontal loop to build around
my fence...

Bruce Jensen

On 8 Sep 2005 10:34:24 -0700, "bpnjensen" wrote:

I find a random wire superior overall to just about any ''tailor
made'' SWL antenna I've tried.

I do find that the dipole is wonderful on 7 MHz, and 11 MHz and up. On
9 and 6 it's about a toss-up, and on down through the tropicals the
wire is better.

My big problem is noise, especially on the lower bands. I have an MFJ
noise cancelling unit that works with the two antennas, but I think two
simpel wires phased would work rather better. If I can arrange such an
array that can be set up on my smallish property, I will let folks
know. Meanwhile, I still have a large horizontal loop to build around
my fence...

Bruce Jensen

I've used the MFJ Noise Canceller with an MFJ-1024 Remote Active
antenna for the noise sense with decent results. Since then I ditched
my Linksys router and 90% of the noise went away.

In article ,
David wrote:

On 8 Sep 2005 08:17:00 -0700, "bpnjensen" wrote:

I agree in general, except for the fact that a dipole has a
characteristic directionality, whereas a random wire significantly
shorter than the wavelength will be omnidirectional. I suspect that
there will be occasional times when this factor matters.

When it doesn't matter, a random wire is still a more versatile antenna
than a single-lambda dipole, even when untuned.

I have an Alpha-Delta DXUltra, which is basically a multi-lambda
dipole, and a 60-foot random wire through a transformer at 20 feet
elevation above ground. Noise levels aside, there is little I can hear
on the DXUltra that doesn't appear on the wire, and quite a bit on the
wire, especially at freqs 6 MHz, that is inaudible on the DXUltra
(even though the DXUltra supposedly is good down to 120 meters - this
loss of signal may be a function of inadequate height, since the
antenna center is only 27 feet sloping to 7 feet at either end).

Bruce Jensen

I find a random wire superior overall to just about any ''tailor
made'' SWL antenna I've tried.

An antenna "tailored" for a frequency will pick up more signal energy on
that frequency than an antenna of the same type that is not resonant at
that frequency.

--
Telamon
Ventura, California

Telamon - I 'theory' you are correct.

In article .com,
"bpnjensen" wrote:

Highly unlikely on receive for the same reason as on transmit.
--
Telamon
Ventura, California

I agree in general, except for the fact that a dipole has a
characteristic directionality, whereas a random wire significantly
shorter than the wavelength will be omnidirectional. I suspect that
there will be occasional times when this factor matters.

When it doesn't matter, a random wire is still a more versatile antenna
than a single-lambda dipole, even when untuned.

I have an Alpha-Delta DXUltra, which is basically a multi-lambda
dipole, and a 60-foot random wire through a transformer at 20 feet
elevation above ground. Noise levels aside, there is little I can hear
on the DXUltra that doesn't appear on the wire, and quite a bit on the
wire, especially at freqs 6 MHz, that is inaudible on the DXUltra
(even though the DXUltra supposedly is good down to 120 meters - this
loss of signal may be a function of inadequate height, since the
antenna center is only 27 feet sloping to 7 feet at either end).

The assertion that RHF made was that resonance on an antenna is not
important on receive and only important on transmit. It is a tried and
true technique to cut a dipole for a certain receive frequency. When an
dipole antenna is at resonance it will generate a larger voltage from a
distant signal on that frequency than other frequencies above and below
it for the same reason more power will be radiated from it on transmit.
Depending on a number of other factors this alone may or may not allow
you to hear a distant station at a level better than the random wire.

The random wire is not omnidirectional and a direction it can pick up a
signal well will depend on frequency, its length, distance from the
ground and a few other things.

That's just the physics of the statements in question. Now if you want
to qualify it with other criteria such as "I can hear the same stuff on
a random wire" that is a different story.

Resonance is an important quality in any antenna. The random wire is
just called random because you are NOT building it with a particular
resonant frequency in mind. A random wire is resonant at some frequency
and will perform better at that point just as a dipole or nearly any
other antenna as a general rule. There are exceptions of course such as
very electrically short antennas designed to be amplified due to the low
efficiency. There resonance is not a factor considered in its operation.

A random wire antenna is half an antenna where the other half is ground.
For it to work well generally means you need a good outdoor RF ground.
This can be a problem itself depending on where you live. A dipole is a
full antenna that does not need an RF ground to work properly.

A random wire is a common mode antenna that will do a good job of
picking up local electrical noise so the criteria is that you need a
good RF ground or radials in its place and you need to live in an
electrically quiet area.

If the Alpha-Delta DXUltra is worth the money you paid for it it should
work better then a "random wire" at some frequencies. Sometimes the
behavior of antennas or circuits is not apparent by only looking at a
small selection of frequencies.

--
Telamon
Ventura, California

For One and All,