开云体育

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


If you've got links, post them in the Links section!


Post files here. If the file comes from a website, please put it in

the Links rather than uploading the file.

You can now view images at higher resolution in Photos. Upload JPG

and GIF into Photos. Please convert BMP or TIF to JPG or GIF before
uploading.

And please trim all this when replying!
Yahoo! Groups Links






---------------------------------
Food fight? Enjoy some healthy debate
in the Yahoo! Answers Food & Drink Q&A.

If you've got links, post them in the Links section!


Post files here. If the file comes from a website, please put it in the Links rather than uploading the file.


You can now view images at higher resolution in Photos. Upload JPG and GIF into Photos. Please convert BMP or TIF to JPG or GIF before uploading.


And please trim all this when replying!
Yahoo! Groups Links







---------------------------------
Be a better Heartthrob. Get better relationship answers from someone who knows.
Yahoo! Answers - Check it out.

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.

At operating frequencies, the potentials of the two arms of the outer
conductor are equal and opposite (again provided that the gap is at the
exact centre). The currents at the gap are equal and opposite. These
currents flow around the end of the arms at the gap, resulting in no net
current at the gap but at the same time resulting in equal and opposite
currents on the inner surface of the shield. These then couple to the inner
conductor(s) and subsequently couple to the receiver.

The frequency at which the outer conductor goes from being an
electrostatic shield to being the actual antenna depends on the conductivity
and thickness of the material. In general, the point is somehwere in the
vicinity of ten to twnety skin depths, depending on whose evaluation you are
using.

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

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
<preynaert@...> 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 <kargo_cult@...> 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


If you've got links, post them in the Links section!


Post files here. If the file comes from a website, please put it in

the Links rather than uploading the file.

You can now view images at higher resolution in Photos. Upload JPG

and GIF into Photos. Please convert BMP or TIF to JPG or GIF before
uploading.

And please trim all this when replying!
Yahoo! Groups Links






---------------------------------
Food fight? Enjoy some healthy debate
in the Yahoo! Answers Food & Drink Q&A.

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

In a message dated 15/05/2007 00:04:14 GMT Daylight Time,
fraser.castle@... writes:




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 ?






------------------------
I think that's a reasonable assumption:-)

In a message dated 14/05/2007 22:20:39 GMT Daylight Time,
davidgriffin@... writes:




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






------------------------------
Interesting question, but "no"

Having said that, grounding the plastic loop on my 5030 probably wouldn't
prove very much:-)

Go on, go drive that stake......
it's the obvious way of proving it, one way or another, and......
since you thought of it first.............:-)

regards

Nigel
GM8PZR

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 <kargo_cult@...> 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


If you've got links, post them in the Links section!


Post files here. If the file comes from a website, please put it in the Links rather than uploading the file.


You can now view images at higher resolution in Photos. Upload JPG and GIF into Photos. Please convert BMP or TIF to JPG or GIF before uploading.


And please trim all this when replying!
Yahoo! Groups Links






---------------------------------
Food fight? Enjoy some healthy debate
in the Yahoo! Answers Food & Drink Q&A.

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

In a message dated 14/05/2007 20:21:50 GMT Daylight Time,
rmoore5@... writes:

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


Hi Rob
Are you sure re the 1530?
Certainly it's true for the 5030 as that's got a plastic tube, and I can
hear the wire rattling around inside it as I'd expect, but I've never heard
anything rattling inside the 1530.
I would expect that you'd see wires going to the potted amp, even if the
tube is the antenna, as the tube will likely mechanically terminate inside the
plastic entry tubes on the electrical junction box used as a housing with
perhaps a screw and solder tag connection at the ends.

regards

Nigel

GM8PZR

--- In loopantennas@..., "Steve Ratzlaff"
<steveratz@...> wrote:

Hi,
I'm familiar with the circuits used in the head end of the older

DX-1 Pro,

and the receiver coupler/supply.
The head end is a basic high-impedance active whip antenna. The

circuit is

an exact clone of the old Ralph Burhans circuit he published back

in the

1980's, using 100% negative feedback.

(SNIPPED)


Hi Steve,

Many thanks for that superb description of the DX-1. You have made
my day as I have been scratching my head about this antennas design
for ages.

When I X-Rayed the mast section it had four wires interconnecting
the various 'loop' arms but I couldn't be sure how they were
connected. They certainly are not all wired in parallel in the MKII.
I was wondering if they had wired the 'loop' arms in series to
effectively compress a long whip into a small space. This bit of the
design still eludes me.

As for the amplifier... your information is invaluable. The MKII
amplifier is stated as providing 10dB gain whereas the MKI was
spec'ed at 6dB gain. The issue of input capacitance is very
interesting indeed. I have some NOS Motorola high power jFETs (or
tFETS ?) that were used in some Watkins Johnson amplifiers that I
maintained. I suspect that these will also exhibit higher than
desirable input capacitance so I will re think using them in any
antenna designs that I build.

Thank you for your excellent help with this question Steve. It does,
however, lead me to wonder about RF Systems performance claims. RFS
make the MLB1 and this has caused much discussion both positive and
negative. I like their AA-150 that was built for the Lowe HF-150 but
it may be no better than any other active whip on the market. It is
well built though. The DX-10 is basically an AA-150 in a different
shell. As for the passive HF magnetic whips and some of their other
exotic designs, I am not sure that these are not just well
engineered 'snake oil' antennas. I own an RF Systems DX-500 which is
beautifully constructed and claims to work upto 500 MHz. I have
found that it needs an excellent groundplane for HF work and is
really just an RF probe (it has an extremely short active element).

Oh well.... it looks like the DX-1 is just an exotic & expensive
active whip pretending to be a loop then :-(

Thanks to everyone for their input on this topic. I'm off to start
saving for a Wellbrook ALA1530+.

Fraser

As a postscript to the RF Systems DX-1 Pro active whip antenna comments I made, WRTH did an extensive review of various active whip antennas perhaps 5 or more years ago. The DX-1 Pro was clearly identified as an active whip antenna then, and was one of the antennas reviewed--it had a good review rating. The newer "MK II" apparently is a recent variation of that same active whip antenna. Perhaps the addition of a common-mode choke on the output of the whipamp is the only change, as I suggested in my previous post.

73,
Steve

Hi,
I'm familiar with the circuits used in the head end of the older DX-1 Pro, and the receiver coupler/supply.
The head end is a basic high-impedance active whip antenna. The circuit is an exact clone of the old Ralph Burhans circuit he published back in the 1980's, using 100% negative feedback. That would account for one of the transformers noted by Fraser. The other transformer is very likely a common-mode choke on the output. My older unit did not have that common-mode choke; it only had the one feedback transformer. I'm guessing the "MK II" means the common-mode choke addition was the only improvement from the original DX-1 Pro.
The active power jfet device RF Systems is using has significant gate-source capacitance, which acts to shunt signals to ground the higher you go in frequency, and loss in sensitivity begins from about 12 MHz and up. They devised the very elaborate "egg beater" cage whip antenna in an attempt to improve the antenna capacitance, to offset the active device shunting effect. The bit in the advertising about reducing polarization effects is purely smoke and mirrors nonsense, and has no effect whatsoever on various signal polarization being received better with that cage whip antenna. There is no voltage gain for this active amplifier circuit, only overall loss from input to output.
The receiver coupler's "+10dB" input position is also a piece of fiction. That position directly couples the antenna's output through the various other parts (switchable BCB filter and dual-output splitter) to the output to the receiver. The other positions, "0" to "-40" are all switched attenuators before going to the BCB filter and splitter, with the "0" position being either -3 dB or -6 dB attenuation ( I forget which). The BCB filter is not designed for the NA BCB frequency range but for Europe.
The active device is very similar to the Crystalonics CP650 power jfet device that Dallas Lankford first discovered would work well in the old Burhans active whip circuit--it too has significant gate-source input capacitance. (This is the device the AMRAD active whip is using; they got their circuit from Dallas Lankford, who was never given proper credit in the article.)
I have been building and experimenting with active whip antennas for a number of years now; I've tested just about every commercially available antenna on the market, from either a hobby standpoint or from when my old company was building active antennas as a Defense Contractor. The DX-1 Pro is the only commercially available antenna that I've tried that I would recommend, despite its increasing loss of sensitivity as you go up the HF frequency range. However, it's very expensive for most hobbyists to even consider purchasing one. And any active antenna performs only as well as the local noise environment it's used in, and of course must be used externally from any dwelling with AC power. The farther from AC power you can mount such an antenna, either horizontal or vertical distance from AC power, the better it can work without being limited by local AC noise.
73,
Steve