wrote:
Has anyone had a "bad", as in less then stellar performance, with a
Wellbrook ALA 1530
loop antenna?

Given the almost sacred refference the Wellbrook is held in I have
debated asking
this question. I have a ALA 1530 that is part of a trade that I am
looking at and
guys I just don't get it. This antenna is reputed to be the cat's meow,
but I have
found it marginal at best. A north country active antenna is nearly
it's match
and the 3rd harmonic of a local MW (770KHz) is S3 on the Wellbrook. A
Lankford Active Dipole stomps it in gain, IP2 and IP3 and for
directivity.

I am wondering if this antenna is defective or if it is a case of the
Emperors New
Clothes. I have tried loops several times in the last 30 years and
always give up
becuase I have never found the reported imunity against local QRM to be
true.
I am building a copy of the WL1030 (http://wl1030.com/), but I don't
understand
the fascination with loops. What am I missing?

For MW DX "big" air loops make sense. Good directivity to null out an
offending
signal. I notice Ron Harding uses McKay 100E with a phaser to achieve
good
nulls. For HF the sky wave "smears" both the desired and unwanted
signals
making a null very iffy.

Receivers used in this test:
R2000
R8B
R390
R392
The R390 and R392 where not tested at my home but at a friend's home
where I have them stored. While I like both the R390 and R392, they are
somewhat awkward to rapidly tune from one frequency to a wildly
seperated
one.

Terry

One thing you might do is check the cables connecting the different
components of the Wellbrook. At one point I noticed that my loop wasn't
performing as I thought it should and I discovered that the cable
connecting the receiver to the antenna interface had a poor connection
where it meets the interface box. The intermittent connection became
obvious as soon as I jiggled the cable a bit.

Also, where do you have the loop situated? In my experience the
performance of the loop is seriously degraded when used indoors.

Steve wrote:


One thing you might do is check the cables connecting the different
components of the Wellbrook. At one point I noticed that my loop wasn't
performing as I thought it should and I discovered that the cable
connecting the receiver to the antenna interface had a poor connection
where it meets the interface box. The intermittent connection became
obvious as soon as I jiggled the cable a bit.

Also, where do you have the loop situated? In my experience the
performance of the loop is seriously degraded when used indoors.

Calbe and connectors are good, and have been used to power
the Lankford active dipole I am checking.

I have tried it in a variety of locations.

We even went so far as to drive to the Red River Gorge, an area well
away
from houses, power lines etc.

The preformance just doesn't strike me as being worth the fairly high
cost.

The active dipole beat it every time.

Terry

In article om,
wrote:

Steve wrote:


One thing you might do is check the cables connecting the different
components of the Wellbrook. At one point I noticed that my loop
wasn't performing as I thought it should and I discovered that the
cable connecting the receiver to the antenna interface had a poor
connection where it meets the interface box. The intermittent
connection became obvious as soon as I jiggled the cable a bit.

Also, where do you have the loop situated? In my experience the
performance of the loop is seriously degraded when used indoors.

Calbe and connectors are good, and have been used to power the
Lankford active dipole I am checking.

I have tried it in a variety of locations.

We even went so far as to drive to the Red River Gorge, an area well
away from houses, power lines etc.

The preformance just doesn't strike me as being worth the fairly high
cost.

The active dipole beat it every time.

That was a self defeating test. The idea here is that you will have a
lower noise floor in a locally noisy area with a shielded loop than a
dipole antenna. There is going to be no advantage to using a loop over
a dipole in an electrically quiet area.

A shielded loop is not better at picking up a distant signal than a
dipole but is less sensitive to local noise generators so in an area
with high local noise you would have better signal to noise than a
full size dipole antenna.

I also expect that a shielded loop would be better than a amplified
electrically small dipole although the difference in advantage would be
smaller than the comparison to a full sized dipole. Depending on the
area a electrically small dipole and shielded loop may not have a
significant difference in local noise floor because you managed to get
both far enough from local noise makers due to their small size.

If you found a problem connection from interface to antenna then I
would suspect your findings. As you well know that connection is the
power supply to the antenna amplifier and the RF path back to the
radio.

"The active dipole beat it every time" is a bit vague. Maybe you could
expand a little on that.

--
Telamon
Ventura, California

" That was a self defeating test. The idea here is that you will have a
lower noise floor in a locally noisy area with a shielded loop than a
dipole antenna. There is going to be no advantage to using a loop over
a dipole in an electrically quiet area.

A shielded loop is not better at picking up a distant signal than a
dipole but is less sensitive to local noise generators so in an area
with high local noise you would have better signal to noise than a
full size dipole antenna.

Please see:
http://www.w8ji.com/magnetic_receiving_loops.htm

Dale W4OP

In article kImTg.111$pS3.23@trnddc01,
"Dale Parfitt" wrote:

" That was a self defeating test. The idea here is that you will have a
lower noise floor in a locally noisy area with a shielded loop than a
dipole antenna. There is going to be no advantage to using a loop over
a dipole in an electrically quiet area.

A shielded loop is not better at picking up a distant signal than a
dipole but is less sensitive to local noise generators so in an area
with high local noise you would have better signal to noise than a
full size dipole antenna.

Please see:
http://www.w8ji.com/magnetic_receiving_loops.htm

A nice page written by some amateur drawing wrong conclusions. Following
his logic coax cable would not shield the center conductor either for
example since the coax has to be open on both ends. He quotes a lot of
good information and then spouts conclusion that don't follow.

I don't have the patience to read the whole page but I scanned through
it and for starters he does not seem to distinguish between far and near
field energy. Far field has equal energy in the E and H fields so two
antennas, example dipole and loop, that are strongly couple to one field
and not the other generate the same power. No real difference then
between antennas that are strongly affected by one field and not the
other to far field signal or noise.

Near field is a different story. Near field is what the local noise
makers generate the most of and the electric tends to propagate farther
than the magnetic from the source so you want to use an antenna that is
sensitive to the H field for the same reason you try to get an antenna
as far away from local noise sources as possible. You can see the logic
in that right?

And let's not forget about that very handy null in the loop pattern. I
use that all the time on the AM portable with its built in loop stick
antenna that is not even shielded.

--
Telamon
Ventura, California

A nice page written by some amateur drawing wrong conclusions. Following
his logic coax cable would not shield the center conductor either for
example since the coax has to be open on both ends. He quotes a lot of
good information and then spouts conclusion that don't follow.

The author of the page is one of the most respected amateurs, an active
consulting engineer, designer of the DX engineering Low band line of active
antennas, and widely published. I have read identical conclusions in the
IEEE Journal on EM.

The null of the loop is its best feature. We agree there.

Dale W4OP

Very interesting post's on this subject so far. Sure is nice to have
some topics that are about DX & radios.

I did a bunch of CW contesting back some years ago & am very familiar
with W8JI's station. All of the best ops in the country wanted to run
his station during the ARRL 160 cw contest. BIG signal & could work
stations most could not even hear.

My point is I am sure he "knows his stuff".

With that said....I have 2 hf antennas up right now. A wellbrook K9AY &
a wellbrook ALA 1530. The 1530 is mounted at 6ft off the ground
strapped to a wooden fence.

The K9AY always has a signal that shows more s-units. However many
times the 1530 will give a better s/n ratio.

It took me a while to "get over" the lower s meter reading & realize I
was hearing the signal better because of the better s/n ratio.

My location is in a housing project with several houses within 300 ft
of me so the loss in gain was not hurting me since my noise floor was
higher.

Now If I were located out in the wide open spaces with no man made
noise for miles then the 1530 would have no where near enough gain.

All of these are my opinions of course


Ken KG4BIG


Dale Parfitt wrote:
A nice page written by some amateur drawing wrong conclusions. Following
his logic coax cable would not shield the center conductor either for
example since the coax has to be open on both ends. He quotes a lot of
good information and then spouts conclusion that don't follow.

The author of the page is one of the most respected amateurs, an active
consulting engineer, designer of the DX engineering Low band line of active
antennas, and widely published. I have read identical conclusions in the
IEEE Journal on EM.

The null of the loop is its best feature. We agree there.

Dale W4OP

In article oZuTg.1266$753.664@trnddc05,
"Dale Parfitt" wrote:

A nice page written by some amateur drawing wrong conclusions.
Following
his logic coax cable would not shield the center conductor either
for example since the coax has to be open on both ends. He quotes a
lot of good information and then spouts conclusion that don't
follow.

The author of the page is one of the most respected amateurs, an
active consulting engineer, designer of the DX engineering Low band
line of active antennas, and widely published. I have read identical
conclusions in the IEEE Journal on EM.

The null of the loop is its best feature. We agree there.

I'm sure he is a great guy and knows a lot but that does not mean he is
right. What he states is against theory and experience. I will go with
what practical experience supported by theory over someone's preeminent
opinion.

His opinion is contrary to the theory of operation of electrically small
shielded (or unshielded for that matter) loops compared to electric
field probes (example single wire or dipole).

You possibly misconstrued what you read in the IEEE journal.

We just had a discussion about inductive noise probes for trouble
shooting problems. Maybe you missed that. It was discussed here about
using a small shielded loop to distinguish between magnetic fields and a
short wire probe to pick up electric fields. Now this past discussion
relates to very close local induction fields. This is the very situation
the author you refer to claims the shielded loop probe would be useless
as it would be no different than the voltage probe response. Well sorry,
these probes really work as advertised because I used them
professionally and successfully.

My experience building and using antennas also run contrary to what the
author you refer to states. My experience in antenna building is also
predicted by theory. Most other people have had similar experiences
using loop and dipole antennas.

Again I will mention that there is a difference between an inductive
field and a far field that is a propagating wave and that theoretically
there will be a significant difference in response between E and H field
sensitive antennas to the inductive but not the far field.

--
Telamon
Ventura, California

Dale Parfitt wrote:
A nice page written by some amateur drawing wrong conclusions. Following
his logic coax cable would not shield the center conductor either for
example since the coax has to be open on both ends. He quotes a lot of
good information and then spouts conclusion that don't follow.

The author of the page is one of the most respected amateurs, an active
consulting engineer, designer of the DX engineering Low band line of active
antennas, and widely published. I have read identical conclusions in the
IEEE Journal on EM.

The null of the loop is its best feature. We agree there.

Dale W4OP

Interesting. I just checked out the DX Engineering website and it's
worth a look:

http://www.dxengineering.com

I learned, among other things, that they'll soon be marketing a very
expensive phasing unit. If it's worth that much, it'll be really
interesting.

Dale Parfitt wrote:
" That was a self defeating test. The idea here is that you will have a
lower noise floor in a locally noisy area with a shielded loop than a
dipole antenna. There is going to be no advantage to using a loop over
a dipole in an electrically quiet area.

A shielded loop is not better at picking up a distant signal than a
dipole but is less sensitive to local noise generators so in an area
with high local noise you would have better signal to noise than a
full size dipole antenna.

Please see:
http://www.w8ji.com/magnetic_receiving_loops.htm

Dale W4OP

Dale [W4OP] - Thanks for the very informative link.
http://www.w8ji.com/magnetic_receiving_loops.htm

Magnetic Loop Antennas Receiving
"Small Receiving Loop Antennas"
http://www.w8ji.com/magnetic_receiving_loops.htm

* Small Loop Antennas are often referred to as "Magnetic Radiators".
Folklore claims a small "Shielded" Loop Antenna behaves like a
sieve, sorting "good magnetic signals" from "bad electrical noise".
http://www.w8ji.com/magnetic_receiving_loops.htm

* Nothing is further from the truth! At relatively small distances a
small Magnetic Loop Antenna is more sensitive to Electric Fields
than a small Electric Field Probe type Antenna.
http://www.w8ji.com/magnetic_receiving_loops.htm

* Field Impedance of the Loop Antenna
http://www.w8ji.com/magnetic_receiving_loops.htm
Loop Antenna Fields - Short Dipole or Vertical Fields - Radiation

* Loop Antenna Shielding and Balance
http://www.w8ji.com/magnetic_receiving_loops.htm

* Examples of Small Loop Antennas
and Analysis of Loop Antenna Construction
http://www.w8ji.com/magnetic_receiving_loops.htm

* Typical Magnetic Loop Antenna
(found on Internet and other places)
http://www.w8ji.com/magnetic_receiving_loops.htm

* Circuit Representations of Shielded Loop Antennas
http://www.w8ji.com/magnetic_receiving_loops.htm