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.

In article .com,
"Ken Wilson" wrote:

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.

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

And this is the experience of most people with loop antennas.

Things are a bit more complicated with electrically small loop antennas
because amplifiers come into use. Now you have to consider amplifier
design along with antenna design to predict performance.

Larger loops require less amplification so the amplifier performance
becomes less of an issue.

Full size loop antennas are a little different dimensionally and
depending on your house lot you might be able to fit a loop on your lot
where you can't fit a full size dipole. This difference in dimensions
may allow you get the full size loop farther away from a local noise
source.

--
Telamon
Ventura, California

In article . com,
wrote:

wrote:

I use the ALA 100. The smaller loops may not be as good on MW. It is a
good idea to insure the amplifer is actually doing something. The fuse
could be blown, the wall wart bad, etc. Unplug the power connector and
make sure the signal strength drops. You will get reception from the
loop even if the amp is off since some RF will leak.

Some of the Wellbrook amps were positive ground. The unit is fused and
I would guess there is a reverse biased protection diode. If the wrong
wall wart was used, it would pop the fuse. In my portable set up, I
have red shrink wrap on the connector that goes to the Wellbrook, just
to make it clear the ground is backwards.

As far as the 1530 goes, it may not have a good resale value since they
released the "plus" version, which has response in the FM BCB.

This ALA 1530 requires a reversed, is shell positve and inner negative,
wall wart. But the center conductor of the coax was positive. I left
the
original power injector/diplexer intact and built my own. I verified
the
problem with the stock wall wart/diplexer before trying my own.

With out power I get virtually no signals. A few very strong MW and SW
at way less then S1. So the amp is working. The original owner says
it always behaved like this. OK, but clearly not the do all end all
of antennas.

What you are calling a "power injector/diplexer" would probably be best
described as a bias-T. This is a three port device:

Sample schematic:
http://www.smelectronics.us/biast.htm

1. DC voltage. (DC input) This is connected to the power supply.
2. AC voltage. (RF output) This is connected to the radio.
3. DC + AC voltage. (RF input, DC output) This is connected to the
antenna/amplifier.

Port 3 to 2 is connected with a capacitor of very low reactance (zero)
to the signal you want to pass through these two ports.

Port 1 to 3 are connect with an inductor, which passes DC voltage from
port 1 to 3 but blocks RF (high Z) going from 3 to 1 so the RF only sees
a path from 3 to 2.

Port 3 and 2 are coax cable and port one could be two terminals. One
terminal is common grounded with the coax shield grounds. Using a ground
independent power supply to the terminals on port 1 allow you to have
either a positive or negative power supply to the remote amplifier.

--
Telamon
Ventura, California

I have a Datong AD-270 = very noisy antenna.
My DX pals have ALA1530's and I would exchange the Datong for a Wellbrook
anyday.

--
John Plimmer, Montagu, Western Cape Province, South Africa
South 33 d 47 m 32 s, East 20 d 07 m 32 s
RX Icom IC-756 PRO III with MW mods
Drake SW8 & ERGO software
Sony 7600D, GE SRIII, Redsun RP2100
BW XCR 30, Braun T1000, Sangean 818 & 803A.
GE circa 50's radiogram
Antenna's RF Systems DX 1 Pro, Datong AD-270
Kiwa MW Loop
http://www.dxing.info/about/dxers/plimmer.dx

wrote in message
ups.com...

Perhaps my local noise floor is "good enough" that whatever benifit the
Wellbrook offers is lost. I am trading the newly aquired ALA 1530 to
an acquaintance who lives in downtown Lexington for a Datong
AD370 that was only used for a few weeks.

He is aware of my doubts about the ALA1530's ability but says he has
nothing to loose. When I get a copy of the WL1030 built we will test it
at his condo.

Terry

In article . com,
wrote:

Ken Wilson wrote:
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 KG4BIGY


Perhaps my local noise floor is "good enough" that whatever benifit the
Wellbrook offers is lost. I am trading the newly aquired ALA 1530 to
an acquaintance who lives in downtown Lexington for a Datong
AD370 that was only used for a few weeks.

He is aware of my doubts about the ALA1530's ability but says he has
nothing to loose. When I get a copy of the WL1030 built we will test it
at his condo.

The models may cover different frequency ranges so the noise floor may
be different for that reason. Be sure to compare apples to apples.

--
Telamon
Ventura, California

In article ,
"John Plimmer" wrote:

wrote in message
ups.com...

Perhaps my local noise floor is "good enough" that whatever benifit
the Wellbrook offers is lost. I am trading the newly aquired ALA
1530 to an acquaintance who lives in downtown Lexington for a
Datong AD370 that was only used for a few weeks.

He is aware of my doubts about the ALA1530's ability but says he
has nothing to loose. When I get a copy of the WL1030 built we will
test it at his condo.


I have a Datong AD-270 = very noisy antenna. My DX pals have
ALA1530's and I would exchange the Datong for a Wellbrook anyday.

What do you mean by noisy?

Since this is an amplified antenna the amplifier will add its own
noise, which can be a little or a lot or maybe you mean the
antenna/amplifier has a lot of gain where the atmospheric noise is loud
or maybe you mean it picks up a lot of local noise sources.

Since you are comparing it to a loop I am guessing you mean you expect
the Wellbrook to pick up less in the way of local noise sources?

--
Telamon
Ventura, California

John Plimmer wrote:
I have a Datong AD-270 = very noisy antenna.
My DX pals have ALA1530's and I would exchange the Datong for a Wellbrook
anyday.

--
John Plimmer, Montagu, Western Cape Province, South Africa
South 33 d 47 m 32 s, East 20 d 07 m 32 s
RX Icom IC-756 PRO III with MW mods
Drake SW8 & ERGO software
Sony 7600D, GE SRIII, Redsun RP2100
BW XR 30, Braun T1000, Sangean 818 & 803A.
GE circa 50's radiogram
Antenna's RF Systems DX 1 Pro, Datong AD-270
Kiwa MW Loop
http://www.dxing.info/about/dxers/plimmer.dx

I mounted the AD370 on a tree and connected it to
the R2000 on the kitchen table. With the PS side
amplifier in the off position there is minimal noise.
Compared to "North Country" or the AMRAD it is very
close. With the never to be cursed enough MW station
on 770KHz and another local on 1240KHz I have some
very constant signals for IMD. The AMRAD is imune,
no mix products, the NC has some minor mix + and
a very weak 2nd and 3rd harmonic that is internal to
the antenna under test. The AD370 has a very slight,
as in right at the noise floor, mix + (770+1240) and
maybe a weak 3rd harmonic of 770 (2,310KHz). Hard
to be sure as it is right at the noise floor. I can only
find it with a FFT window.

With the additional amplifier the noise floor really jumps up.
A better amp would likely be the Lankford "ultra linear amp"
at http://www.kongsfjord.no/

At this point I have NO regrets about the trade.


Terry

The Datong is mounted next to my DX-1 and generates considerably more noise
Firstly from a poor amplifier and secondly
It is prone to magnifying the local suburban electrical noise which the DX1
doesn't do.
The Datong consists of two five foot whips which can be mounted
horizontally, when it then exhibits the characteristics of a dipole, or it
can be mounted vertically when it performs like a typical vertical whip
antenna. I use it in the vertical position for best results (but noisy).
The Datong is rather poor on MW, but as the frequency gets higher it
performs considerably better. So by 27 megs it outperforms any other antenna
I have used.

I do not own a ALA1530, but two of my pals do, one of whom lives in an inner
city urban environment. It is considerably quieter than his longwires.

--
John Plimmer, Montagu, Western Cape Province, South Africa

"Telamon" wrote in message
...
In article ,
"John Plimmer" wrote:

I have a Datong AD-270 = very noisy antenna. My DX pals have
ALA1530's and I would exchange the Datong for a Wellbrook anyday.

What do you mean by noisy?

Since this is an amplified antenna the amplifier will add its own
noise, which can be a little or a lot or maybe you mean the
antenna/amplifier has a lot of gain where the atmospheric noise is loud
or maybe you mean it picks up a lot of local noise sources.

Since you are comparing it to a loop I am guessing you mean you expect
the Wellbrook to pick up less in the way of local noise sources?

--
Telamon
Ventura, California

Telamon wrote:

1. DC voltage. (DC input) This is connected to the power supply.
2. AC voltage. (RF output) This is connected to the radio.
3. DC + AC voltage. (RF input, DC output) This is connected to the
antenna/amplifier.

Port 3 to 2 is connected with a capacitor of very low reactance (zero)
to the signal you want to pass through these two ports.

Port 1 to 3 are connect with an inductor, which passes DC voltage from
port 1 to 3 but blocks RF (high Z) going from 3 to 1 so the RF only sees
a path from 3 to 2.

Port 3 and 2 are coax cable and port one could be two terminals. One
terminal is common grounded with the coax shield grounds. Using a ground
independent power supply to the terminals on port 1 allow you to have
either a positive or negative power supply to the remote amplifier.

--
Telamon
Ventura, California

It is clear you work in the microwave satellite part of electronics.

In the "good old days", circa 1990, most text and other refference
sources
reffered to them as "power injectors" or "diplexers". Your discription
of it's
function is correct. A power source is isolated from the RF with an
inductor,
or strip line version, and a capacitor blocks the DC from the receiver.

MiniCircuits has very nice, as in wide band, inductors. Since I may use
the same coax for VLF. LF, MW, HF, or VHF my power inject, bias
"T" or diplexer has different inductors in series because I couldn't
find
a single inductor to cover from 10KHz through ~500MHz. I found that by
using smaller chokes that were effective at UHF, with larger chokes for
each decade decrease in frequency. One of the changes I am making
is to use the MC wide band inductors to allow a smaller package to
be used. Space is at a premium in my "shack".

My shack is the 2nd bath with the plumbing removed and covered.
It is 5' by 10'. I prefer the word cozy over cramped.

Terry