On Dec 10, 4:13 pm, wrote:
I suspected there are many people who lurk but will never post in a
public arena.
After my experiences with a cyber-stalker I can understand their
hesitance.

A SWL in Scotland asked me about a comment I made regarding antennas
in
one of my RFI diatribes.

Sorry for the delay, but I ran this past some friends of varying
technical skill levels,
to insure that first my answers are technically accurate, and as
simple as I can get,
while maintaining accuracy.

Get the wood out to start the fire to burn me at.

There are really only three types of HF antennas.
Dipoles
Loops
Surface or Traveling wave.

Of these, only the Traveling wave antenna relies on the earth below it
for it't basic
operation. Dipoles will be effected by the presence of the earth below
them, but a
dipole will operate just fine in free space. Loops are somewhat less
effected by
the earth, but they to will operate just fine in free space.

A traveling wave antenna, beverage or 'long wire' relies on the soil
below the elevated conductor. For most of us Beverages and true 'long
wires' for anything
below 30MHz isn't practical. We simply don't have the real estate
needed to
erect one.

Loops are loops. Many people swear by them, but I have yet to be
impressed.
If you must have a loop investigate the WL1030 as it compares very
well to
the famed Wellbrook ALA1530. I owned a for a few weeks and in a head
to
head test with the WL1030 the WL1030 was always as good as or better
then
the ALA1530. The WL1030 specifies a hard to find Litz wire that
shouldn't stop
anyone. I tried the specified Litz wire and a solid and a stranded
wire and I
couldn't tell any difference. It is true that I didn't do extensive
tests below MW.
I am not into NDBs.

The typical 50 to 100' random wire is barely a longwire antenna at
10M, but at
2M, 146, it is a true longwire. But it is also an extremely poor
antenna at those frequencies.

Now for the part that labels me a Apostate.

The random wire antenna many of us use is a dipole in disguise.
The elevated wire is the obvious element. The earth is the non obvious
element. The earth is generally a very poor conductor and also has
significant reactance.

In locations that are very quiet RF wise, the random wire can be an
excellent
antenna. Since most SWLs are interested in signals that literally come
from
every direction, a random wire can be the best as in most efficient
antenna
for the money and effort.

But very few of us live in such locations. They do exist. I am lucky
enough to
have a friend with a cabin deep in the Daniel Boone National forest.
There
are now power lines, telephone lines or anything but trees for at
least a half
mile. If you want power bring batteries or a genset. To get there you
need a
high clearance 4WD or horses. Or to be 18 and young and healthy.

In that location I don't bother with complex antennas because they
would be
a complete waste of time.

Since most of us live and listen in a location served by at least a
power
utility that supplies us those vital electrons, we will generally have
to deal
with much more noise then a remote location experiences.

I have been lucky enough several times to experience widespread power
outages during the winter, and the listening is a true joy. Of course
one does
get cold at night.....

What many SWLs and hams refuse to accept is that dipole that is
designed,
or 'cut', for a specific frequency, say 10MHz will work far from the
design
frequency. Of course as you move away from the design frequency the
electrical balance of the 'dipole' will suffer.

An example. 10MHz has a wave length of 30M. So, ignoring end effects,
each leg should be 7.5M, or ~29'. But this dipole will perform very
well
down to at least 540KHz. I once contracted to build a WWV antenna
system
for a laboratory's master clock. They supplied the receiver and I got
paid to
come up with a workable antenna. I used Pansonic RF2200 as my test
receiver. And the dipole worked great. I oriented so Bolder CO was
broadside,
or on the main lobe. Just for grins tuned down expecting reception to
abruptly
stop at maybe 8MHz. I had excellent reception all the way down to
540KHz, WKRC in Cincinnati OH, about 100miles north of the antenna and
way off the
gain lobe. With 20' of coax life was good, This was a WINNER. However,
at the
receiver end of the coax, some 150' away, while WWV on 10, and 20 MHz
were perfect, and WWV at 15 wasn't to bad, WWV at 5 and the MW band
was a mix of noise. They called me in one night because they had to
down the
building power but had to keep the receiver clock and 2 experiments
"on line".
I installed a power divider so I could use an auxiliary receiver for
testing, so after
we switched everything to battery power while the power utility
changed a couple
of transformers. Problems developed and the substation that fed the
lab had
to be powered down as well. There was nearly no equipment on in the
lab.
Very quiet RF wise. And guess what, the same antenna, feedline and
power divider that before had only produced a horrible mix of RF noise
below about
9MHz, suddenly was very quiet. I had quiet a time that night tuning
around
and I was amazed at how good the reception was. I should have caught
on
then and there just how important the general RF noise level around
the antenna
is. I missed a excellent chance to learn something useful to my hobby
and
put me several years ahead of the game.

What I am leading up to is the radical thought that for many of us,
the all too
common random wire antenna is almost certainly a very poor antenna.
By
using the poorly conductive soil as part of your 'dipole' you are
dooming yourself
to noise problems. If the noise is around, you will receive it.

People like DXace do a masterful job with a ~250' antenna and a simple
ground
rod. Most of us will need a much more sophisticated antenna and ground
if we
choose to use a random wire.

Instead of a single 8' NEC ground rod, at a minimum you will need the
8' ground
rod and a radial running back under the antenna to your home.
Wellbrook shows
one way to accomplish this.http://www.wellbrook.uk.com/longwire.html
I disagree with his acceptance of 100' as a long wire for HF
reception, but his
diagram shows an excellent way to improve the antenna and to keep
noise from
within your home away from the antenna.

I prefer to feed the antenna 50 to 100' away from the house, and to
run it away
from the home. And to run at least one, and if possible 3 wires under
the
antenna. A center wire with outriders about 6" out, and the 'radial'
or 'counter
poise' connected at each end and a 8' ground rod at each end. It is
very useful
to bury the coax at least 6" underground and 12" is even better. This
helps
choke off any common mode noise and may be effective enough that
further
RFI remediation is not needed.

After years of messing around with a variety of antennas. The AmRad
was a
fair design and I was impressed to find out it was a poor clone of an
antenna
designed by Dallas Lankford. I have been impressed with all of
Dallas's antennas.
I have not used a random wire antenna for a year now and I am enjoying
greatly improved reception. Check out http://www.kongsfjord.no/dl/
dl.htm.

I had great success with his 15' relay tuned antenna. I live too close
to a couple
of MW stations that drive most active antennas 'nuts'. All of Dallas's
antennas
worked fine, but I wanted a low power drain antenna.

I am presently using his: http://www.kongsfjord.no/dl/Antennas/
Simplified%20Complementary%20Push-Pull%20Output%20Active%20Whip
%20Antennas%20II.pdf
and it is a very good antenna. The only issues I have are my trusty
R2000 isn't
quite up to the task, so I now use a Drake R8B. This antenna is almost
a miracle.
The parts won't break anyone's piggy bank and is not terribly
complicated.

Only by understanding how our antennas really work can we hope to
minimize the
noise we receive and maximize the desired signals. No antenna can said
to be
truly "noise reducing", but a good antenna, properly isolated from the
noisy home,
and by using a good feed line, we can at least not couple noise from
our home
into our antenna(s).

To be completely accurate and fair, it must be noted that in the last
year or so
I have taken serious steps to eliminate RF noise at their sources. But
tests performed at non radio friends whose homes have no RFI
treatments and
the Lankford Micro Active antenna works very well there also.

For true weak signal DX be prepared to spend some time analyzing your
home grown noise sources and plotting how to eliminate them.

Terry

-
- What many SWLs and hams refuse to accept is that dipole
- that is designed, or 'cut', for a specific frequency,
- say 10MHz will work far from the design frequency.
- Of course as you move away from the design frequency
- the electrical balance of the 'dipole' will suffer.
-

Is the Dipole Antenna 'Good Enough' for most Shortwave Listeners ?

Yes for most Shortwave Radio Listeners (SWLs) a Dipole Antenna
can work very well as a SWL Antenna.

TIPS - On How-To-Making a Dipole Antenna Wide-Banded and
Omni-Directional for Shortwave Radio Listenig (SWL).

1 - Use a 4:1 Matching Transformer at the Center-Point.

2 - Use a Coax Cable as a Feed-in-Line from the
Dipole Antenna to the Shortwave Radio/Receiver.

3 - Elevate the Dipole Antenna's Center-Point 'twice'
(2X) the Height of the Ends.
* Dipole's Center-Point 16~32 Feet High
* Dipole's Ends 8~16 Feet High
Modifies the basic Dipole Antenna into a 'Sloping'
Inverted"V" Antenna.

4 - A Fifty Foot (50') [Random-Lenght] Dipole Antenna
That is 50-Feet Tip-to-Tip -or- 25-Feet for each Arm.
http://www.hamuniverse.com/dipivcal.html
Puts you around the center of the 31 Metre Shortwave
Radio Band (~9.33 MHz)

So Yes -IMHO- The Dipole Antenna is Good Enough for most
Shortwave Listeners to Hear What They Want To Hearing !

iane ~ RHF