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Did you try to ground both (and at the same time) left and right side of the Al tube, close to the plastic case, to the ground of the coax? Otherwise, grounding as you discribed has indeed little or no effect. The "loop" is in these cases just being formed by the wire that you use to create the ground connection.

Patrick.

Rob Moore <rmoore5@...> wrote: Well, I went out and both grounded the loop to the shell of the BNC
connector and also tried grounding it to a ground rod I had put in
previously. The results were......... No change. I had my G313E
set to pick up WWV on 5000Khz and was doing screen captures in-
between each test and honestly couldn't see any difference, either
in the signal levels or in the noise floor. Nothing, Nada, Nil.
Before you ask, I tried grounding the tube at 45, 90, and 180
degrees and lightly sanded it so a decent connection would be made.

I also checked on the screws because someone here had said that they
had an ALA-1530 and the Aluminum loop had a couple of screws in it
about 2 cm from the loop base. There were no screws or holes to
indicate missing screws either. Hmmm. Either this person was
trying to describe this Antenna from memory or he has some other
kind of loop. I can verify that I have a Wellbrook ALA-1530
(Standard version) that works quite well. (If anyone wants to come
see it or or my ALA-100 setup, you're welcome to come.) The only
screws I could see were actually in the plastic antenna base and
they were sheet metal screws used to secure the aluminum tube to the
plastic, which I don't think could also be used to secure wires to
the tube.

Rob




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Hi Rob,

inside the tube, the wires are connected to these srews with AMP clamps (you know, you press them on a cable and they have a little U-shape or O-shape to put a screw through.

Patrick.

Rob Moore <rmoore5@...> wrote:The only
screws I could see were actually in the plastic antenna base and
they were sheet metal screws used to secure the aluminum tube to the
plastic, which I don't think could also be used to secure wires to
the tube.




---------------------------------
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Well, I went out and both grounded the loop to the shell of the BNC
connector and also tried grounding it to a ground rod I had put in
previously. The results were......... No change. I had my G313E
set to pick up WWV on 5000Khz and was doing screen captures in-
between each test and honestly couldn't see any difference, either
in the signal levels or in the noise floor. Nothing, Nada, Nil.
Before you ask, I tried grounding the tube at 45, 90, and 180
degrees and lightly sanded it so a decent connection would be made.

I also checked on the screws because someone here had said that they
had an ALA-1530 and the Aluminum loop had a couple of screws in it
about 2 cm from the loop base. There were no screws or holes to
indicate missing screws either. Hmmm. Either this person was
trying to describe this Antenna from memory or he has some other
kind of loop. I can verify that I have a Wellbrook ALA-1530
(Standard version) that works quite well. (If anyone wants to come
see it or or my ALA-100 setup, you're welcome to come.) The only
screws I could see were actually in the plastic antenna base and
they were sheet metal screws used to secure the aluminum tube to the
plastic, which I don't think could also be used to secure wires to
the tube.

Rob

If you actually took a look at a Wellbrook, you would see that the
design has the coax shield as a common gnd point. Unless the aluminim
ring is "hot" with respect to common, it should not cause any power
problems to connect them.


Rob

--- In loopantennas@..., "antloopernew" <dgmfield@...>
wrote:

I was taking apart some old disk drives and had a thought.

Could the old disk platters be used to construct capacitors.

They are rigid. I am not sure what they are made of.

Dave

Hi Dave,

Hard disk drive platters can be made of two materials, aluminium alloy
or glass.

Most common 3.5" hard drive platter use aluminium alloy coated with the
ferro magnetic layer for the data. Miniature units such as 2.5" laptop
and PCMCIA hard drives often use aluminium alloy platters as well but I
have seen some that used glass that is coated with the ferro data
layer.

Great care is needed when salvaging parts out of Hard Disk Drives.The
hardened glass platters are extremely dangerous if they shatter. My
employer used to require hard disks be dismantled for data destruction
purposes but we were suffering so many hand injuries from the sharp
head arms and platters that it was stopped for health and safety
reasons. The drives can now be disintegrated complete anyway.

As this is a Loop antenna Group I should make a Loop related reference
in this message.......

In the former USSR there was a company making television loop antennas
out of large (approx 14") aluminium scrap winchester hard drive
platters. For those who don't remember, these look like giant versions
of the modern 3.5" hard drive platters. The antenna 'manufacturer'
would cut a 1/4" wide slot in the paltter from the outside edge to the
centre hole. The platter then formed a perfect loop for TV reception !
The loop was screwed to a wooden broom handle and open ribbon feeder
attached either side of the slot using small screws. I had to test one
of these loops and was surprised at how well it actually worked.
Russian recycling in the 1990's :-) The loops sold for around 50 US
Cents.

Fraser

John,

At the bottom of the Wellbrook ALA-1530 information page, there is a
calibration chart which show the Aantenna factor vs frequency. It
indicates that the antenna factor is roughly 8 over most of the range.

How did you come up with a .45 factor?

Rob



--- In loopantennas@..., crabtreejr@... wrote:

The actual antenna factor is about -7dB, ie ca. 0.45, ie the antenna

output is ca. 0.45 volts for a field strength of 1 volt per meter. The
required antenna gain is then +33 - 7 = 26dB.

Hey Everyone;

Newbie/first poster here. So 'hello'.

Been following the Wellbrook saga with great interest.
Warning: While not a hands-on expert, I have read enough about active
loops to be concerned about shorting the Wellbrook's feed line to
prove anything. Yes, the Wellbrook has DC running the coax to feed
the active electronics at the loop base. IE, both sides of the coax
are hot w/ respect to ground. If you want to prove/disprove whether
the aluminum loop is the active element or an RF shield, why not clip
the aluminum loop itself straight to earth ground? I beleive if the
aluminum loop is shield, you will observe an increase in noise but
little effect on gain. If the loop is the active element, you should
notice a huge drop in gain/sensitivity.

Hope that helps.

Mark in Milwaukee
x-WB9AQI

A new amplified loop design has been posted by Dallas Lankford on
kongsfjord.no - inspired by postings by John KC0G on this group.

Bob

Hello Rob

The left hand scale is in dB, and is the correction which would need to be
applied to get a unity antenna factor. So the actual performance is the inverse
of the scale. One would expect the actual performance to decrease with
frequency.

So the actual antenna factor is ca. -7dB or 0.45 (ie 10^(-7/20)) over most of
the hf frequencies.

The cross check is the value of 0.5 which Andy Ikin gave in his article in
Medium Wave News in March 1998. See:
A. Ikin, Broadband Loop Aerials (part 1), Medium Wave News, Jan 1998, pp
13-16
A. Ikin, Broadband Loop Aerials (part 2), Medium Wave News, Mar 1998, pp 9-12

Medium Wave News is published by the Medium Wave Circle. See:
www.mwcircle.org
I have not checked, but suspect that these articles are not available online.

You will note that a couple of the other Wellbrook loops have a slightly
higher gain, with a quoted antenna facro of 1.0 and/or 0dB.

HTH and 73

John KC0G



In a message dated 5/15/07 1:54:28 PM Central Daylight Time,
rmoore5@... writes:

John,

At the bottom of the Wellbrook ALA-1530 information page, there is a
calibration chart which show the Aantenna factor vs frequency. It
indicates that the antenna factor is roughly 8 over most of the range.

How did you come up with a .45 factor?

Rob

--- In loopantennas@..., crabtreejr@... wrote:

The actual antenna factor is about -7dB, ie ca. 0.45, ie the antenna

output is ca. 0.45 volts for a field strength of 1 volt per meter. The
required antenna gain is then +33 - 7 = 26dB.

***
See what's free at .

I was taking apart some old disk drives and had a thought.

Could the old disk platters be used to construct capacitors.

They are rigid. I am not sure what they are made of.

Dave

Hi Dave,

Just got home. I wasn't planning on shorting the aluminum tube to
the center condicutor of the cable. Just to the shell of the BNC
connector, which doesn't have any power on it.

Thanks for the intruction information. I bought my ALA-1530 used
and it didn't come with any instructions.

Rob


--- In loopantennas@..., "n2chi" <davidgriffin@...>
wrote:

Rob,
I just found my 1530 instruction sheet and it reminded me that the

coax

has DC voltage on it (for the circuitry up at the loop base)so

don't

short it out. Also, it does say to NOT ground the coax between

the loop

and the downstream Antenna Interface box "as it may introduce

noise."

Nigel: Not to worry about my using a stake; my wife won't let me

play

with anything sharp any more.
Dave

Rob,
I just found my 1530 instruction sheet and it reminded me that the coax
has DC voltage on it (for the circuitry up at the loop base)so don't
short it out. Also, it does say to NOT ground the coax between the loop
and the downstream Antenna Interface box "as it may introduce noise."
Nigel: Not to worry about my using a stake; my wife won't let me play
with anything sharp any more.
Dave

--- In loopantennas@..., "Rob Moore" <rmoore5@...> wrote:

Hi Dave,

Well the shield is grounded by the time it gets into the house but
maybe I'll try it both ways. That may take a little longer.

Rob



--- In loopantennas@..., "n2chi" <davidgriffin@> wrote:

Hi Rob,
I think I'd try something I'm more sure is grounded. If I remember
correctly, the coax shield between the loop and the electronics is

NOT

grounded. I seem to remember the installation materials saying NOT

to

ground that section of coax. So shorting the aluminmum of the loop

to

the shell of the BNC might not yield a ground. But then, that would
probably short out the antenna?
Dave


--- In loopantennas@..., "Rob Moore" <rmoore5@> wrote:

I have one up a tree and can try that tonight. I assume that
grounding the aluminum loop to the shell of the BNC connector is

what

you're referring to?

Rob

--- In loopantennas@..., "n2chi" <davidgriffin@> wrote:

Does someone have a Wellbrook loop in a convenient enough

location to

ground the shield and see what happens? If it's the antenna,

then

it

won't act like one when grounded. If it's not the antenna, would

there

be any noticeable effect of grounding it? Please don't make me

got

out

and drive a stake in the ground......
Dave

--- In loopantennas@..., gandalfg8@ wrote:

In a message dated 14/05/2007 21:08:36 GMT Daylight Time,
christrask@ writes:

Patrick is absolutely correct in stating that the aluminum

shield

(aka

the outer conductor)is the actual antenna. This is the manner

in

which

shielded loops function at their operating frequency. At very

low

frequencies where most electrical field noise exists, the

currents

and

voltages of both arms of the outer conductor are equal in both

potential and

polarity (provided the gap is at the exact centre), with the

currents

being

the same on both surfaces of the outer conductor material and

zero at

the

gap. The currents that are coupled to the inner conductor(s)

cancel

so that

there is no net noise current delivered to the receiver.



-------------------------------------

Hi Chris

The Wellbrook isn't a shielded loop antenna.

There no gap in this loop, other than inside the housing at the

bottom

where

it connects to the amp.

regards

Nigel

GM8PZR

Hi Dave,

Well the shield is grounded by the time it gets into the house but
maybe I'll try it both ways. That may take a little longer.

Rob



--- In loopantennas@..., "n2chi" <davidgriffin@...> wrote:

Hi Rob,
I think I'd try something I'm more sure is grounded. If I remember
correctly, the coax shield between the loop and the electronics is NOT
grounded. I seem to remember the installation materials saying NOT to
ground that section of coax. So shorting the aluminmum of the loop to
the shell of the BNC might not yield a ground. But then, that would
probably short out the antenna?
Dave


--- In loopantennas@..., "Rob Moore" <rmoore5@> wrote:

I have one up a tree and can try that tonight. I assume that
grounding the aluminum loop to the shell of the BNC connector is what
you're referring to?

Rob

--- In loopantennas@..., "n2chi" <davidgriffin@> wrote:

Does someone have a Wellbrook loop in a convenient enough

location to

ground the shield and see what happens? If it's the antenna, then

it

won't act like one when grounded. If it's not the antenna, would

there

be any noticeable effect of grounding it? Please don't make me got

out

and drive a stake in the ground......
Dave

--- In loopantennas@..., gandalfg8@ wrote:

In a message dated 14/05/2007 21:08:36 GMT Daylight Time,
christrask@ writes:

Patrick is absolutely correct in stating that the aluminum shield

(aka

the outer conductor)is the actual antenna. This is the manner in

which

shielded loops function at their operating frequency. At very low
frequencies where most electrical field noise exists, the currents

and

voltages of both arms of the outer conductor are equal in both

potential and

polarity (provided the gap is at the exact centre), with the

currents

being

the same on both surfaces of the outer conductor material and

zero at

the

gap. The currents that are coupled to the inner conductor(s)

cancel

so that

there is no net noise current delivered to the receiver.



-------------------------------------

Hi Chris

The Wellbrook isn't a shielded loop antenna.

There no gap in this loop, other than inside the housing at the

bottom

where

it connects to the amp.

regards

Nigel

GM8PZR










[Non-text portions of this message have been removed]

Ref. Is it shoelded or not ?

Didn't we read earlier in the groups messages that Patrick had been
kind enough to dismantle an ALA1530 ? Surely if Patrick says his
dismantled ALA1530 had connections from the amp input to the aluminium
loop we can take it that the ALA1530 is not shielded ?

Fraser

Hi Rob,
I think I'd try something I'm more sure is grounded. If I remember
correctly, the coax shield between the loop and the electronics is NOT
grounded. I seem to remember the installation materials saying NOT to
ground that section of coax. So shorting the aluminmum of the loop to
the shell of the BNC might not yield a ground. But then, that would
probably short out the antenna?
Dave


--- In loopantennas@..., "Rob Moore" <rmoore5@...> wrote:

I have one up a tree and can try that tonight. I assume that
grounding the aluminum loop to the shell of the BNC connector is what
you're referring to?

Rob

--- In loopantennas@..., "n2chi" <davidgriffin@> wrote:

Does someone have a Wellbrook loop in a convenient enough location to
ground the shield and see what happens? If it's the antenna, then

it

won't act like one when grounded. If it's not the antenna, would

there

be any noticeable effect of grounding it? Please don't make me got

out

and drive a stake in the ground......
Dave

--- In loopantennas@..., gandalfg8@ wrote:

In a message dated 14/05/2007 21:08:36 GMT Daylight Time,
christrask@ writes:

Patrick is absolutely correct in stating that the aluminum shield

(aka

the outer conductor)is the actual antenna. This is the manner in

which

shielded loops function at their operating frequency. At very low
frequencies where most electrical field noise exists, the currents

and

voltages of both arms of the outer conductor are equal in both

potential and

polarity (provided the gap is at the exact centre), with the

currents

being

the same on both surfaces of the outer conductor material and

zero at

the

gap. The currents that are coupled to the inner conductor(s)

cancel

so that

there is no net noise current delivered to the receiver.



-------------------------------------

Hi Chris

The Wellbrook isn't a shielded loop antenna.

There no gap in this loop, other than inside the housing at the

bottom

where

it connects to the amp.

regards

Nigel

GM8PZR

The Wellbrook isn't a shielded loop antenna.

There no gap in this loop, other than inside the housing at the bottom

where

it connects to the amp.

Oh. That's very different. Never mind.

Chris

,----------------------. High Performance Mixers and
/ What's all this &#92; Amplifiers for RF Communications
/ extinct stuff, anyhow? /
&#92; _______,--------------' Chris Trask / N7ZWY
_ |/ Principal Engineer
oo&#92; Sonoran Radio Research
(__)&#92; _ P.O. Box 25240
&#92; &#92; .' `. Tempe, Arizona 85285-5240
&#92; &#92; / &#92;
&#92; '" &#92; IEEE Senior Member #40274515
. ( ) &#92;
'-| )__| :. &#92; Email: christrask@...
| | | | &#92; '.
c__; c__; '-..'>.__

Graphics by Loek Frederiks

I have one up a tree and can try that tonight. I assume that
grounding the aluminum loop to the shell of the BNC connector is what
you're referring to?

Rob

--- In loopantennas@..., "n2chi" <davidgriffin@...> wrote:

Does someone have a Wellbrook loop in a convenient enough location to
ground the shield and see what happens? If it's the antenna, then it
won't act like one when grounded. If it's not the antenna, would

there

be any noticeable effect of grounding it? Please don't make me got out
and drive a stake in the ground......
Dave

--- In loopantennas@..., gandalfg8@ wrote:

In a message dated 14/05/2007 21:08:36 GMT Daylight Time,
christrask@ writes:

Patrick is absolutely correct in stating that the aluminum shield

(aka

the outer conductor)is the actual antenna. This is the manner in

which

shielded loops function at their operating frequency. At very low
frequencies where most electrical field noise exists, the currents

and

voltages of both arms of the outer conductor are equal in both

potential and

polarity (provided the gap is at the exact centre), with the

currents

being

the same on both surfaces of the outer conductor material and

zero at

the

gap. The currents that are coupled to the inner conductor(s) cancel

so that

there is no net noise current delivered to the receiver.



-------------------------------------

Hi Chris

The Wellbrook isn't a shielded loop antenna.

There no gap in this loop, other than inside the housing at the

bottom

where

it connects to the amp.

regards

Nigel

GM8PZR










[Non-text portions of this message have been removed]

Does someone have a Wellbrook loop in a convenient enough location to
ground the shield and see what happens? If it's the antenna, then it
won't act like one when grounded. If it's not the antenna, would there
be any noticeable effect of grounding it? Please don't make me got out
and drive a stake in the ground......
Dave

--- In loopantennas@..., gandalfg8@... wrote:

In a message dated 14/05/2007 21:08:36 GMT Daylight Time,
christrask@... writes:

Patrick is absolutely correct in stating that the aluminum shield (aka
the outer conductor)is the actual antenna. This is the manner in which
shielded loops function at their operating frequency. At very low
frequencies where most electrical field noise exists, the currents and
voltages of both arms of the outer conductor are equal in both

potential and

polarity (provided the gap is at the exact centre), with the currents

being

the same on both surfaces of the outer conductor material and zero at

the

gap. The currents that are coupled to the inner conductor(s) cancel

so that

there is no net noise current delivered to the receiver.



-------------------------------------

Hi Chris

The Wellbrook isn't a shielded loop antenna.

There no gap in this loop, other than inside the housing at the bottom

where

it connects to the amp.

regards

Nigel

GM8PZR










[Non-text portions of this message have been removed]

Nigel is correct. The Wellbrook isn't a shielded loop antenna.

There are actually two wires that run into each leg aluminum loop that
provides structural support for the antenna and come out the other
side of the loop. I believe (but haven't disassembled it this far
because it wouldn't be of much use after that) that the entire loop is
filled with the potting compound. That's why you don't hear any wires
rattling.

The Wellbrook is a very well constructed, fairly straightforward loop,
which relies on an excellent balanced preamp design and careful
construction to minimize noise pickup.

Rob

--- In loopantennas@..., gandalfg8@... wrote:

In a message dated 14/05/2007 21:08:36 GMT Daylight Time,
christrask@... writes:

Patrick is absolutely correct in stating that the aluminum shield (aka
the outer conductor)is the actual antenna. This is the manner in which
shielded loops function at their operating frequency. At very low
frequencies where most electrical field noise exists, the currents and
voltages of both arms of the outer conductor are equal in both

potential and

polarity (provided the gap is at the exact centre), with the

currents being

the same on both surfaces of the outer conductor material and zero

at the

gap. The currents that are coupled to the inner conductor(s) cancel

so that

there is no net noise current delivered to the receiver.



-------------------------------------

Hi Chris

The Wellbrook isn't a shielded loop antenna.

There no gap in this loop, other than inside the housing at the

bottom where

it connects to the amp.

regards

Nigel

GM8PZR

hi Rob,

regarding the ALA1530:
there is indeed a wire that from the PCB into the Al tube, but this is connected with the tube by a small screw, about 2cm away from the plastic enclosure. So, in my opinion, the Al tube is the actual antenna.

Best regards,
Patrick

Rob Moore <rmoore5@...> wrote: Patrick,

You are wrong that the Aluminim is the actual antenna. There are
wires inside of it and it is only there as a mechanical support. I
know this because I've removed the potting material from one of these
to find out. This can also be verified by examining the 5030. It is
a semi-ridgid version of the ALA-1530.

Rob




This--- In loopantennas@..., Patrick Reynaert

wrote:

Hi,

the wellbrook is not a shielded antenna, the Aluminium tube is the

actual antenna.

Shielding (with a gap of course) a loop only shields it from

electrical noise at very low frequecies, i.e. at frequencies where the
shield thickness is less than the skin depth. At higher frequencies,
where the shield is thicker than the skin depth, the shield only helps
to get a better balance, and hence a better 'null' in the reception
pattern.

Patrick.
Hue Miller wrote: Wellbrook antenna: is the loop

shielded? I am guessing maybe not,

since its performance still seems to be good into the VHF range.
IF not - will shielding such a loop, be worthwhile to diminish
electrical field noise?
I am thinking a "Hula Hoop" toy might be a basis for a homemade
loop. Cut open the loop, feed wire thru it, and glue back together.
Maybe with aluminum foil wrapped around the thing, for shielding,
and amplifier module attached right to the loop.

WL1030 page - i very much look forward to reading the material
there. I just wonder why it is necessary to "register". What is the
thinking behind that?
-Hue Miller


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