The "TRICK" to TV 'type' Coax Cable [Shielded] SWL Loop Antennas {RHF}
RHF
The "TRICK" to TV 'type' Coax Cable [Shielded] SWL Loop Antennas {RHF}
http://groups.yahoo.com/group/Shortwave-SWL-Antenna/message/1626
I too tried to build a Coax Cable [Shielded] Loop Antenna
that was made of "TV type Coax" that had a 'Shield' made
of Foil and about 33% Braid. The Results were very poor.
Then I Got An IDEA "*" ! { K I S S }
Why not use "Pre-Made" Parts :o) WHAT ?
* One Piece of TV type Coax Cable with the "F" Connectors
on both Ends. This can should be these Pre-Made Lengths
Three Feet (3 Ft); Six Feet (6 Ft); Nine Feet (9 Ft);
Twelve Feet (12 Ft); and Fifteen Feet (15 Ft); ETC.
* One "F" Connector to PL-259 Plug (SO-239 Adapter)
RadioShack Catalog # 278-258
* One TV type Two-to-One Splitter with "F" Connectors.
Get the one with the two Output "F" Connectors on
'opposite' Sides and the Input "F" Connector on the
Bottom (looks like a 'T').
THE SECRET IS TO BUILD A <NEXUS> LOOP-HUB:
Using the Two-to-One Splitter. Remove the 'Seal' Plate
from the Body of the Splitter. Remove the Ferrite Core
and Wires from inside the Splitter. Next clean a 'Spot'
inside the Body of the Splitter for a Solder Ground-Point.
Use a Solder Gun (150W) to make this Solder Ground-Point;
get in and get out quickly so that you do not melt the
plastic insulation inside the "F" Connectors. Wrap a
Wire around the Left "F" Connector Terminal. Route this
Wire to the Solder Ground-Point on the Body of the Splitter.
Using a Soldering Iron (35W) and Solder the Left Terminal
and the Ground-Point. Next 'wrap' a Wire around the
Bottom "F" Connector Terminal; and 'route' the Wire to
the Right "F" Connector Terminal. Then you need to make
a 'new' "Metal Cover" for the Splitter. I used one of
those old AOL CD "Tins" that come in the Mail. They are
thin enough to 'cut' with a Heavy Pair of Scissors .
Cut and Trim a piece until it "Fits". Ensure your have
good Metal-to-Metal 'contact' between the Cover and
the Spliter and Glue them together for Security. You
now have the <NEXUS> "LOOP-HUB" of your Coax Cable Loop
Antenna.
The Three Feet (3 Ft) piece of Coax Cable is your
Feed-in-Line.
MAKING YOUR "INTERCHANGABLE" LOOP ANTENNA ELEMENTS:
The Six Feet (6 Ft); Nine Feet (9 Ft); Twelve Feet
(12 Ft) and Fifteen Feet (15 Ft) Coax Cable are your
[Shielded] Loop Antenna Elements. Fold them End-to-End
and 'mark' a One Inch (1") Area at the Fold as their
Mid-Point. Very Carefully 'cut' the Outer Insulation
and then the Foil and Wire Braid away and out from this
One Inch Area. {Do Not Damage the Inner Insulation and
Center Wire of the Coax Cable.) Tape this One Inch Area
and an Inch on each side for Strength and Security.
TIP: If you have a Plastic Hula-Hoop or some 5/8" or
3/4" (White) Low Pressure Water Line Polyethylene Tubing
as a "Form" to hold the Loops in a Circle Shape. This
Tubing must 'slip-over' the Coax Cable's "F" Connectors.
THE LOOP ANTENNA "HOOK-UP":
* Slide the Coax Cable Loop Antenna Element into the
Plastic Tubing.
* Connect your Coax Cable Loop Antenna Element to the
LOOP-HUB {Splitter}.
* Connect your Coax Cable Feed-in-Line to the LOOP-HUB
{Splitter}.
* Install the "F" Connector to PL-259 Plug to the
'other end' of your Coax Cable Feed-in-Line and Connect
to the your Radio/Receiver.
* Shape and Position your Loop Antenna Element.
CAUTION: When Installing the Coax Cable "F" Connectors
into the "F" Connectors of the LOOP-HUB: Be careful to
make sure that the Center Wire is NOT Bent and Shorted-Out.
SIZING: This is a Low Noise SWL InDoor Loop Antenna that
allows the 'changing' of the Loop Antenna Element for the
Coverage of different Shortwave Bands. These Loops are 'cut'
"Sized" to roughly One Tenth of a Wave Length (1/10WL)
* Twenty-Five Feet (25 Ft) roughly the 120 Meter SW Band
* Twenty Feet (20 Ft) roughly the 90 Meter SW Band
* Fifteen Feet (15 Ft) roughly the 75 Meter SW Band
* Twelve Feet (12 Ft) roughly the 60 Meter SW Band
* Nine Feet (9 Ft) roughly the 41 Meter SW Band
* Six Feet (6 Ft) roughly the 31 Meter SW Band
* Five Feet (5 Ft) roughly the 25 Meter SW Band
* Four Feet (4 Ft) roughly the 19 Meter SW Band
* Three Feet (3 Ft) roughly the 13 Meter SW Band
The above Lengths and SW Bands are 'based' on the low
cost common {RadioShack} TV type RG-59 Coax Cable with
a Velocity Factor of 0.66.
NOTE: If you use RG6 "Quad Shield" Coax Cable that has
a Velocity Factor of 0.78 to 0.82: Then every thing would
shift down one SW Band 120M>90M, 90M>75M, 75M>60M, ETC.
PACK-AND-GO "TRAVEL" LOOP ANTENNA:
This Design-Set-Up makes for a 'portable' Travel SWL Loop
Antenna that can be Taken-Down and Put-Up in a Minute or two.
MEGA-SIZED FIFTY FOOT LOOP FOR THE AM/MW BROADCAST BAND:
Take a Fifty Foot (50 Ft) piece of Coax Cable and Mount
it OutSide Doors
- 540 kHz to 1700 kHz with a MidPoint of 1120 kHz
- Fifty Feet (50 Ft0 [1/10WL] VF=0.66 using RG59 Coax Cable.
- Square shape 12.5 Feet per Side with 17.5 Cross-Arms.
- Round shape 16 Diameter Circle.
- Coax Cable Lead-in-Line 5-10 Feet.
This is roughly the "Sizing" for the AM/MW Broadcast Band
For DX-Peditions throw a 50 Foot Coax Loop Antenna Element
Over a Tree Limb about 15 Feet High and stretch-out the two
bottom side to form an Equilateral Triangle 17 Feet on a side.
Hook-Up everything and sit-down and Listen :o)
iane ~ RHF
.
Some Say: On A Clear Day You Can See Forever.
http://groups.yahoo.com/group/Shortwave-SWL-Antenna/message/502
I BELIEVE: On A Clear Night...
You Can Hear Forever and Beyond - The Beyond !
.
.
= = = In gccloopant...@yahoogroups.com,
= = = "YODAR" <yodar@in O'do> wrote:
> I MADE MY FIRST ONE AND FLOPPED because I used TV Coax
> (RG 58?) and there was no braid, it was foil and I
> could make no solder connection...ARRGGGG
>
> The RG-8 second try was so ungainly and costly and
> unyielding of ANY signal (perhaps I had failed with
> a connection) , that I got irrigated (kind way of
> saying P***ed OFF!) and threw it out.
>
> If I mess with Coax again it will be for an attic
> SNAKE ANTENNA
>
> Yodar in O'do
> who is still using SLINKIES
>
.
Dale Parfitt
"RHF" <rhf-new...@pacbell.net> wrote in message
news:ff3145e8.04102...@posting.google.com...
> YODAR,
>
> The "TRICK" to TV 'type' Coax Cable [Shielded] SWL Loop Antennas {RHF}
> http://groups.yahoo.com/group/Shortwave-SWL-Antenna/message/1626
>
> I too tried to build a Coax Cable [Shielded] Loop Antenna
> that was made of "TV type Coax" that had a 'Shield' made
> of Foil and about 33% Braid. The Results were very poor.
>
> Then I Got An IDEA "*" ! { K I S S }
>
> Why not use "Pre-Made" Parts :o) WHAT ?
hardline. A CATV junction box for the termination and wideband preamp ( no
tuning) and the standard 3/4" CATV connectors.
Here's some pix:
http://www.parelectronics.com/pics_new/P1010023.JPG
http://www.parelectronics.com/pics_new/P1010024.JPG 1
meter version
http://www.parelectronics.com/pics_new/P1010025.JPG
http://www.parelectronics.com/pics_new/P1010026.JPG
close up of hub and preamp
http://www.parelectronics.com/pics_new/P1010027.JPG gap
assembly
http://www.parelectronics.com/pics_new/P1010028.JPG 7'
version
--
Dale W4OP
for PAR Electronics, Inc.
Mark Keith
> YODAR,
>
> The "TRICK" to TV 'type' Coax Cable [Shielded] SWL Loop Antennas {RHF}
> http://groups.yahoo.com/group/Shortwave-SWL-Antenna/message/1626
>
> I too tried to build a Coax Cable [Shielded] Loop Antenna
> that was made of "TV type Coax" that had a 'Shield' made
> of Foil and about 33% Braid. The Results were very poor.
Hummm... It *should* have worked just fine. Besides being lousy to
solder to, there is nothing wrong with a foil shield. Thats solid
coverage, and better than strands of wire. The coax shield for a SW or
MW loop should be fairly non critical. The only purpose is to ensure
balance. MK
Telamon
nm...@wt.net (Mark Keith) wrote:
"The Results were very poor" is not very much information to go on to
any conclusion or solution.
Maybe he was expecting more output from the loop than he got. A shielded
loop that is not very large is not going to have a big output. Maybe he
screwed up and did not have a shield gap.
--
Telamon
Ventura, California
Yodar
(printed for use)
Thanks a million
yodar
RHF
= = = news:<telamon_spamshield-2...@newssvr13-ext.news.prodigy.com>...
MK & TELAMON,
My reason for stating that the performance was 'poor' had to do with
may small problems:
* Learning Curve - It was my first Coax Cable [Shielded] Loop
Antenna.
* Questionable 'quality' of the old RG-59 Coax Cable being used.
[ Learned to use 'new' better quality Coax Cable. ]
* Trouble getting a good 'connection' at the Bottom-Joint between
the Aluminum Braid.
[ Learned to use more exposed Braid to make 3-4 complete Wraps
around the other section of Exposed Braid at the Bottom-Joint. ]
IDEA: Got the Idea for the LOOP-HUB using a 'modified' TV
type Two-Way Splitter.
* The "F" Connector' End had a Center Wire that was 'short' and
resulted in an intermittent connection when moved.
[ Learned to make sure that the Center Wire was Long Enough
and that I did NOT Bend them and Short-them-Out when installing
them. ]
The basic design of the "GreerTech" Coax Cable [Shielded] Loop
Antenna is good and very practical.
LOOP=> http://www.greertech.com/hfloop/mymagloop.html
My 'second' Coax Cable [Shielded] Loop Antenna was made from
Thirteen Feet (13 Ft) of standard size RG-8 Coax Cable.
* Big and difficult to work with.
* Easy to get a good 'connection' at the Bottom-Joint.
The most recent Coax Cable [Shielded] Loop Antenna was made from
a standard 'pre-made' Twelve Feet (12 Ft) of RG-6 'Quad Shield'
Coax Cable.
* RG-6 is 'easy' to work with.
* Pre-Made Lengths with "F" Connectors already attached.
* Just 'cut' the One Inch "Gap" at the Center of the Length.
* Easy to get a good 'connection' at the Bottom-Joint using the
LOOP-HUB made from a TV type Two Way Splitter.
RESULTS: Very Good Performance. (Equal to the 13 Ft RG-8 Loop.)
NOTE: Lessons Learned.
Mark Keith
>
> My reason for stating that the performance was 'poor' had to do with
> may small problems:
>
> * Learning Curve - It was my first Coax Cable [Shielded] Loop
> Antenna.
>
> * Questionable 'quality' of the old RG-59 Coax Cable being used.
> [ Learned to use 'new' better quality Coax Cable. ]
The coax shouldn't matter much at all...
>
> * Trouble getting a good 'connection' at the Bottom-Joint between
> the Aluminum Braid.
> [ Learned to use more exposed Braid to make 3-4 complete Wraps
> around the other section of Exposed Braid at the Bottom-Joint. ]
That could cause a problem...
>
> IDEA: Got the Idea for the LOOP-HUB using a 'modified' TV
> type Two-Way Splitter.
>
> * The "F" Connector' End had a Center Wire that was 'short' and
> resulted in an intermittent connection when moved.
> [ Learned to make sure that the Center Wire was Long Enough
> and that I did NOT Bend them and Short-them-Out when installing
> them. ]
>
>
> The basic design of the "GreerTech" Coax Cable [Shielded] Loop
> Antenna is good and very practical.
> LOOP=> http://www.greertech.com/hfloop/mymagloop.html
I notice he likes PVC...I do also...About the easiest frame you can
build for a loop...Here is one design I have used...
http://web.wt.net/~nm5k/loop5.jpg
>
>
> My 'second' Coax Cable [Shielded] Loop Antenna was made from
> Thirteen Feet (13 Ft) of standard size RG-8 Coax Cable.
Kinda heavy....:/
>
> * Big and difficult to work with.
Yep...
>
> * Easy to get a good 'connection' at the Bottom-Joint.
>
>
> The most recent Coax Cable [Shielded] Loop Antenna was made from
> a standard 'pre-made' Twelve Feet (12 Ft) of RG-6 'Quad Shield'
> Coax Cable.
>
> * RG-6 is 'easy' to work with.
>
> * Pre-Made Lengths with "F" Connectors already attached.
>
> * Just 'cut' the One Inch "Gap" at the Center of the Length.
>
> * Easy to get a good 'connection' at the Bottom-Joint using the
> LOOP-HUB made from a TV type Two Way Splitter.
>
> RESULTS: Very Good Performance. (Equal to the 13 Ft RG-8 Loop.)
>
> NOTE: Lessons Learned.
I've tried a few coax loops, and I guess they are ok, but in general,
I prefer the normal solenoid windings using plain wire... Much
lighter, and the performance *if properly balanced* , is the same. I
only use variable caps to tune the loop. My present loop that I use
the most is a diamond, appx 44 inches per side, and has 5 turns. "The
PVC frame is about 6 ft tall, counting the mast below the loop
winding, and the cross arm is 5 ft across" I use a multi gang
variable for tuning, and it has a switch to change to a small value
gang for upper freq range use. Also have some fixed caps to tack on if
I want to listen to LF. With all the cap variations, the tuning range
is about 250kc to about 2500 kc or so. But it's usually used on MW and
160m. It's indoors on a stand thats next to me on the floor and
rotates...MK
RHF
Connecting your TV 'type' Coax Cable [Shielded] SWL Loop Antenna
to your Table Top Shortwave Receiver or 'Portable' AM/FM/Shortwave
Radio.
Table Top Shortwave Receivers:
For "Receivers" with a SO-239 Jack for the External Antenna
you can use an "F" Jack to PL-259 Plug (SO-239 Adapter)
RadioShack Catalog # 278-258
'Portable' AM/FM/Shortwave Radios:
For "Radios" with a 1/8" Mono-Jack for the External Antenna
you can use an "F" Jack to 1/8" Plug (1/8" Mono-Jack Adapter)
RadioShack Catalog # 278-257
~ RHF
.
.
= = = rhf-new...@pacbell.net (RHF) wrote in message
= = = news:<ff3145e8.04102...@posting.google.com>...
Gene Gardner
This seems like a good place to insert a discussion about a
"shielded loop" being a myth for anything except for deeper
nulls in the directivity pattern: (these were posted about
18 months ago).
------------------------------------------------------------
------------------------------------------------------------
From: Roy Lewallen <w7...@eznec.com>
Date: Fri, 21 Mar 2003 11:30:17 -0800
Newsgroups: sci.electronics.design,alt.engineering.electrical,rec.radio.amateur.antenna
Subject: Re: Loop Antenna questions
It's fairly easy to see that what Tom wrote (the first paragraph of
quoted material below) is true. "Shielding" a loop simply moves the
feedpoint to the gap, and the outside of the "shield" becomes the loop.
It's no more or less immune to electric fields than any other loop. What
"shielding" does (and all it does) is to increase rejection of common
mode excitation, improving loop balance and the resulting pattern null
in practical installations. The sensitivity of a "shielded" loop to both
electric and magnetic fields is exactly the same as for an "unshielded"
loop.
The myth that "shielding" a loop somehow rejects the electric field
without affecting the magnetic field is one that's been kicking around
the amateur community for decades. I don't suppose it'll ever die.
Another thing that seems to be unknown or overlooked is that a small
(so-called "magnetic") loop antenna is actually more sensitive to an
electric field and less sensitive to a magnetic field than a short
("electric") dipole, at all distances from the antenna unless the
radiation source is very close -- within less than a wavelength.
Roy Lewallen, W7EL
JLB wrote:
>>The external "metal toroid" is then the antenna, for it is on the
>>outside of that "toroid" that antenna currents must exist, and not
>>inside it. The gap is then the feedpoint, to which the internal wire
>>couples and then acts as a simple feedline. To best reject response
>>to electric fields, the gap must be properly positioned...
>>
>
>
> No, the gap is usually opposite the feed point and the sheild is grounded.
> It shields the loop from electric fields but it still responds to magnetic
> fields. This is common practice and the idea has been around for many
> decades. From personal experience I can say that it makes a tremendous
> difference in the sensitivity pattern of the loop, even when extremely close
> to other conductors (including AC house wiring).
>
>
>>References available on request.
>>
>
> Ok, what are they?
>
> Jim
> N8EE
>
>
>
From: Roy Lewallen <w7...@eznec.com>
Date: Fri, 21 Mar 2003 22:52:21 -0800
Newsgroups: sci.electronics.design,alt.engineering.electrical,rec.radio.amateur.antenna
Subject: Re: Loop Antenna questions
After some reflection, I see that I can't really justify the statement I
made. Thanks for questioning it.
Let me explain what I do know. The following discussion assumes that all
antennas are lossless, to eliminate a factor that would obscure the
subject under discussion.
If you put 100 watts into a very short dipole, the ratio of the E field
it produces to the H field it produces is called the wave impedance. At
a distance of considerably less than a wavelength, or greater, this
ratio is about 377 ohms (in air or free space), and E and H are in
phase. The same thing is true for a very small loop antenna, or any
other small antenna. If you get far enough away, the E/H ratio is the
same for any kind of antenna, although you might have to get a farther
from an antenna that's large in terms of wavelength. Invoking the
reciprocity principle, you find that the relative response of a small
loop to E and H fields is the same as for a small dipole if the field
originates some distance from the antenna. The so-called "magnetic" loop
responds just the same as any other antenna to fields originating beyond
a wavelength or so from the antenna.
What's interesting is the relative strength of radiated E and H fields
close to the antenna. My overstatement was the implication that the
ratio of E to H transmitted fields represent relative "sensitivity" to E
and H fields when receiving. Contrary to what the CFA and EH proponents
claim, it's not possible to generate E and H fields independently. And
contrary to what people who misunderstand "shielded" loops say, it's not
possible to isolate E and H fields. (It is possible to change the
impedance of a wave -- that is, the E/H ratio -- in a region, but it
always reverts back to the impedance of the medium -- 377 ohms for free
space -- within a pretty small distance of the disturbance.) So
sensitivity to an E or H field is somewhat problematic, since you can't
create either one in isolation for a test. Consequently, I'll just
discuss the E and H fields that the antennas produce when transmitting.
I believe that an antenna with high transmit E/H ratio will be
relatively insensitive to a wave with low E/H ratio (which would have to
be created nearby), and vice-versa. But I can't quantify the
relationship. I only know it involves the concept of transfer impedance,
and I haven't given the topic enough study to say more about it. It is
discussed in a number of texts, for those who are interested.
What I've done is look at the E/H ratio radiated by a small loop and a
small dipole at various distances, in the direction of the maximum far
field radiation (in the plane of the loop and broadside to the dipole).
The following analysis was done with EZNEC/4 using its double precision
NEC-4 calculating engine. This was necessary because of problems NEC
codes have with very small loops, and the size of loop I chose was too
small for analysis with NEC-2. However, it could probably be done with
MININEC, or it could be done with an NEC-2 based program like the EZNEC
demo if the loop is made a bit larger. It's vital to set the loss to
zero so that a negative feed point impedance isn't concealed by positive
loss resistance. I've gotten email from a person who was skeptical of
the results and did the calculations analytically. He came to the same
conclusion, which gives me added confidence in the results. The
following calculations were done at 3 MHz (100 meter wavelength).
Here's what happens. A small loop is sometimes called a "low impedance"
antenna because of the low E/H ratio close to the antenna. This might be
adequate justification for calling it a "magnetic" antenna as amateurs
have taken to doing, but the term unfortunately conveys the mistaken
impression that the antenna somehow responds only to or more strongly to
magnetic fields coming far from the antenna, which isn't true. But very
close to the antenna, the E/H ratio is indeed lower than the 377 ohm
value this ratio always has far from the antenna. In exactly
complementary fashion, a small dipole is a "high impedance" antenna,
having an E/H ratio higher than 377 ohms very close to the antenna. Here
are the values of the magnitude of E/H for a 2 meter (1/50 wavelength)
circumference octagonal loop and a 2 meter long dipole at 3 MHz. The
distance is measured from the center of the loop or dipole, and the
direction is in the plane of the loop or broadside to the dipole.
Distance (m) E/H (ohms)
Dipole Loop
2 2630 63.9
4 1360 110
6 862 169
8 597 241
10 440 326
12 345 414
14 291 490
16 265 538
18 257 555
20 258 552
22 264 538
24 273 522
26 281 506
28 290 491
30 297 478
50 342 415
100 367 386
The curious thing is that, while the dipole field impedance is high
close to the dipole, and low close to the loop, in both cases it
overshoots 377 ohms by a considerable amount, reaching a peak (lowest Z
for the dipole and highest for the loop) at about 18 meters, then
asymptotically approaches 377 ohms from the "wrong side" beyond that. At
all distances of 12 meters (about 1/8 wavelength) and beyond, the E/H
ratio of the loop is actually higher than that of the dipole! That was
the basis for my original statement. Whatever might be said about the
"sensitivity" of a "magnetic" loop to E and H fields, it certainly can't
be said to be more sensitive to H fields, or less sensitive to E fields,
than a small dipole, at any distance greater than about 1/8 wavelength.
The exact sizes of the loop and dipole aren't important. The near fields
at these distances are essentially equal for all small dipoles and for
all small loops for a given input power, provided that they're much
smaller than a wavelength in any dimension.
Roy Lewallen, W7EL
Reg Edwards wrote:
> Roy says -
>
>
>>- - - - a small
>>(so-called "magnetic") loop antenna is actually more sensitive to an
>>electric field and less sensitive to a magnetic field than a short
>>("electric") dipole - - - -
>
>
> -----------------------------------------------------
>
> Roy,
>
> What are your units of "sensitivity"?
>
> How are things to be measured (even hypothetically) and compared?
>
> In any case, the statement is meaningless unless loop diameter and dipole
> length are incorporated.
>
> Explanation please.
>
> A simple learned reference will not be of much use since 99.9 percent of
> readers will have no chance of ever getting their hands on it.
>
> Yours, Reg, G4FGQ
>
>
>
>
>
From: Roy Lewallen <w7...@eznec.com>
Date: Sat, 22 Mar 2003 13:15:46 -0800
Newsgroups: sci.electronics.design,alt.engineering.electrical,rec.radio.amateur.antenna
Subject: Re: Loop Antenna questions
Richard Clark wrote:
> If anything, your work contributes to the notion of these "notable"
> differences rather than eliminates them. You forcefully detail how
> different the short dipole is from a small loop to exactly the same
> degree as offered by CFA/EH proponents as that being its boon - even
> if they invert the rationale of what constitutes the sensitivity.
> This is to say, that if they are entirely wrong about a magnetic
> antenna being sensitive to the magnetic field (something you reject
> and offer compelling numbers as evidence); they do have a point about
> the magnitude of difference (they are not entirely wedded to the
> principle as they are the effect - if in fact that effect is not
> another figment of wish fulfillment).
My understanding of the CFA/EH antenna is undeniably vague, but I think
it goes something like this: The E and H fields are created
independently, one by a capacitor-like part of the antenna and the other
by a coil-like part of the antenna. This, as I said and as many others
have pointed out, can't be done. Creation of a time-varying E field
always results in a time-varying H field, and vice-versa. The E and H
fields thus "independently" created are done so in the ratio of 377
ohms. This being the ratio of the the components in the far field, the
direct synthesis results in the lack of a near field. This lack of near
field is credited somehow with the magical properties of these antennas
(high efficiency despite small size) by mechanisms that have never been
clear to me. At any rate, these wonderful properties have never been
demonstrated with either believable measurements or modeling despite
more than a decade of hype, so it sure looks like they're fiction also.
The EH antenna further distinguishes itself by requiring a magic
inductor whose current at one terminal is shifted in phase 90 degrees
from the current at the other terminal, adding yet another layer of
impossibility.
If I've misinterpreted the explanations for how these things are
supposed to work, I apologize -- it wasn't intentional.
> The argument about being less sensitive to neighborhood noise for
> magnetic antennas, small loops, or loops in general, seems to be
> justified by your data supporting very different E/H ratios out to
> about 10M, which for me is easily the most disruptive region to any
> antenna in a noisy neighborhood and makes that case in some sense.
It might. Remember, though, that this is constant in terms of
wavelength, so the range drops by a factor of two at twice the
frequency. (But on the other hand, the range will be greater at 160
meters.) Also, note that the difference isn't very great even at a
distance of 10 meters. You have to get very close indeed to see a truly
major difference. I suspect that major differences in interference
rejection are as likely to be due to differences in balance (causing
better or worse nulls) or polarization.
> It seems to me that the difference applies only to situations where
> that first 10M is significant, and to what degree coupling of
> interference within that region becomes meaningful.
Yes, that's the conclusion I reach.
Roy Lewallen, W7EL
RHF
Interesting Information, Thank You for the Repost.
Somewhere, I remember reading that a Coax Cable [Shielded] Loop
Antenna is simply an End-Fed Dipole that is Terminated on Itself.
The fact that it is a Dipole (Electrically Balanced) and the Loop
Shape (Physically Balanced) give it it's inherent properties.
~ RHF
.
.
= = = ge...@csl.uiuc.edu (Gene Gardner) wrote in message
= = = news:<clqv4o$duv$1...@news.ks.uiuc.edu>...
Telamon
ge...@csl.uiuc.edu (Gene Gardner) wrote:
> This seems like a good place to insert a discussion about a
> "shielded loop" being a myth for anything except for deeper
> nulls in the directivity pattern: (these were posted about
> 18 months ago).
> ------------------------------------------------------------
> ------------------------------------------------------------
< Snip >
It is a good example of why I do not read rec.radio.amateur.antenna.
Anything you read in it has about a 50% chance of being correct. It is
up to you to figure out which is right. If I want to read a thesis, I'll
crack a textbook where I stand a better chance of not being misled. With
technical articles, I also do not have to deal with terms like, myth,
oldwives tails, or requests for citations and the like.
--
Telamon
Ventura, California
Mark Keith
>
> Anything you read in it has about a 50% chance of being correct. It is
> up to you to figure out which is right. If I want to read a thesis, I'll
> crack a textbook where I stand a better chance of not being misled. With
> technical articles, I also do not have to deal with terms like, myth,
> oldwives tails, or requests for citations and the like.
And r.r.s differs from this how? They spread just as much crap here,
as they do there....Probably more...And much more OT's and radio
whacko's to boot...BTW, I happen to agree with the "thesis". I don't
believe in "low noise" antennas. Anyone who believes a shielded loop
is "quieter" than a non shielded loop needs a reality check. So in
that, I'm glad he posted the "thesis". Old wives tales need to be shot
down.....Over and over...Until dead. :( BTW, I don't have a cessna
citation, so they will be out of luck in that dept...I do fly a lear
31a on my simulator a lot though. MK
Telamon
Well, OK there is just as much crap here but the posts in RRS do not
usually turn into a "thesis" or degenerate into soap operatic techno
babble with the usual cast of characters.
Generally, the air of pretense does not exist in RRS, as people here do
not claim to be other than nonprofessional on the subject.
Oh yeah and you are wrong about the shielded loop.
--
Telamon
Ventura, California
clifto
> Generally, the air of pretense does not exist in RRS, as people here do
> not claim to be other than nonprofessional on the subject.
I am a professional shortwave listener, as my mother once gave me a dime
to go listen to the radio.
--
So those 380 tons of missing explosives were moved by Saddam before all
those expert inspectors noticed, eh?
No wonder twelve years of inspections found NOTHING.
Telamon
clifto <cli...@clifto.com> wrote:
> Telamon wrote:
> > Generally, the air of pretense does not exist in RRS, as people here do
> > not claim to be other than nonprofessional on the subject.
>
> I am a professional shortwave listener, as my mother once gave me a dime
> to go listen to the radio.
What's her address? I'm going to send her a bill for my listening hours.
She may need a new mortgage on the house.
--
Telamon
Ventura, California
Mark Keith
>
> usually turn into a "thesis" or degenerate into soap operatic techno
> babble with the usual cast of characters.
Where was the technobabble? It made sense to me...
>
> Generally, the air of pretense does not exist in RRS, as people here do
> not claim to be other than nonprofessional on the subject.
Well, some on rraa *are* professionals. But again, many are not. I am
not. My work has nothing at all to do with radio, antennas...
>
> Oh yeah and you are wrong about the shielded loop.
Oh yeah? Prove it. I've built both, and tested both, and I couldn't
tell a lick of difference. I have also used both shielded loops and
plain wire loops for the "coupling" loop that feeds a regular wire
loop. Again, no difference in noise pickup.
None whatsoever. If I am wrong, why don't I see the results? I'm not
just barking at the moon. I've built and compared both types just to
test this exact theory. Both of my present loops are now plain wire.
Don't you think that if there were really an advantage to a shielded
loop, I would be using them? My mama didn't raise a total fool. If I
see something that works according to common lore, I'll say so. If it
doesn't , I'll say that too...So far, I haven't seen it...
It's still my opinion that the shielded loops *do* help ensure balance
in feeding, but as far as a magical "anti noise" property, I don't see
it. If you feed the plain wire loop in a manner that also ensures the
same balance, both antennas will respond to any noise in the same
manner. You can disagree, which is fine, but until I see proof of this
magical anti noise property in real life, I will continue to claim the
*lower noise with a shielded loop theory* is a bunch of malarky... MK
Telamon
nm...@wt.net (Mark Keith) wrote:
> Telamon <telamon_s...@pacbell.net.is.invalid> wrote in message
> >
> > Well, OK there is just as much crap here but the posts in RRS do not
> > usually turn into a "thesis" or degenerate into soap operatic techno
> > babble with the usual cast of characters.
>
> Where was the technobabble? It made sense to me...
Well it did not make sense to me. One thing was said and then the
contrary was stated, then the the one sided discussion went off on
another tangent and then on to some thing else. The thread read like a
voyage of discovery and was not unlike babbling.
> >
> > Generally, the air of pretense does not exist in RRS, as people here do
> > not claim to be other than nonprofessional on the subject.
>
> Well, some on rraa *are* professionals. But again, many are not. I am
> not. My work has nothing at all to do with radio, antennas...
> >
> > Oh yeah and you are wrong about the shielded loop.
>
> Oh yeah? Prove it. I've built both, and tested both, and I couldn't
> tell a lick of difference. I have also used both shielded loops and
> plain wire loops for the "coupling" loop that feeds a regular wire
> loop. Again, no difference in noise pickup.
> None whatsoever. If I am wrong, why don't I see the results? I'm not
> just barking at the moon. I've built and compared both types just to
> test this exact theory. Both of my present loops are now plain wire.
> Don't you think that if there were really an advantage to a shielded
> loop, I would be using them? My mama didn't raise a total fool. If I
> see something that works according to common lore, I'll say so. If it
> doesn't , I'll say that too...So far, I haven't seen it...
> It's still my opinion that the shielded loops *do* help ensure balance
> in feeding, but as far as a magical "anti noise" property, I don't see
> it. If you feed the plain wire loop in a manner that also ensures the
> same balance, both antennas will respond to any noise in the same
> manner. You can disagree, which is fine, but until I see proof of this
> magical anti noise property in real life, I will continue to claim the
> *lower noise with a shielded loop theory* is a bunch of malarky... MK
No, I'm not proving basic theory and design to you over Usenet. This is
the wrong newsgroup for that. Go play in rec.radio.amateur.antenna
Besides you have have already stated experimental results contrary to
basic theory and practice to your own satisfaction. How am I going to
challenge that?
Sorry Markey I'm not playing rec.radio.amateur.antenna game. Go play
with the other "Professional Trolls."
--
Telamon
Ventura, California
Tom Donaly
Actually, Mark is right. For small loops it shouldn't make any
difference according to the theory in the Antenna Engineering
Handbook. Shielding larger loops may help deepen the null, which
is good for direction finding, but it isn't supposed to do anything
for small loops.
73,
Tom Donaly, KA6RUH
Mark Keith
>
> the wrong newsgroup for that. Go play in rec.radio.amateur.antenna
rec.radio.shortwave is the wrong ng for an antenna related debate????
And we are talking about a receive antenna used by many MWL's, not one
used by hams for transmitting. Wrong NG???
Shit, all that off topic crap must have warped your frigging brain....
I guess if it ain't off topic, or written by some ignorant SOB that
just wants to stir up controversy about Bush/Kerry "dumb and dumber",
it don't belong....Get a grip...
>
> Besides you have have already stated experimental results contrary to
> basic theory and practice to your own satisfaction. How am I going to
> challenge that?
By providing contrasting experimemental results or data... How else???
Are you presently under experimental medication, or are you normally
this slow?
>
> Sorry Markey I'm not playing rec.radio.amateur.antenna game. Go play
> with the other "Professional Trolls."
Well, Telley, I take this to mean you can't provide contrasting
results or data to refute my claims...Fine. Go play with yourself
then. But every time I see you cut down rraa for no good reason, as
you have seen you do a few times recently, I'm gonna jump your ass
like stink on a turd. If you can't take the heat, keep out of the
kitchen. No one has a gun to your head, making you read certain posts,
even if crossposted. And if you disagree with someones "thesis", why
don't you just provide contrasting data or results to refute his
claims. Seems it would be more useful that acting like a jackass, and
calling him a troll, thesis writer, or whatever goofball tag you want
to attach. MK
Telamon
nm...@wt.net (Mark Keith) wrote:
Hey Markey here is how this is going to work.
< Plonk >
--
Telamon
Ventura, California
RHF
What you may be missing, is that the 'average' End-User of the
Coax Cable [Shielded] Shortwave Listener's (SWL) Loop Antenna
is simply 'interested' in the "Practical Application" and RESULTS
Gain from using [The Device].
Their "Focus Is:
* How To Build/Buy It.
* How To Use It.
* What To Expect From It.
The 'target' "Reader" of the 'original' "Post" was the everyday
Shortwave Listener { No License Required } .
Know Your Reader - Communicate Effectively - KISAP !
[ Keep It Simple And Practical ! ]
REMEMBER: What Works... WORKS ! { No Theory Required }
iane ~ RHF
.
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= = = nm...@wt.net (Mark Keith) wrote in message
= = = news:<25eb70d7.04110...@posting.google.com>...
Mark Keith
>
>
> < Plonk >
What a chicken shit Telley is.... MK
Mark Keith
> MK,
>
> What you may be missing, is that the 'average' End-User of the
> Coax Cable [Shielded] Shortwave Listener's (SWL) Loop Antenna
> is simply 'interested' in the "Practical Application" and RESULTS
> Gain from using [The Device].
No I'm not missing anything.
>
> Their "Focus Is:
> * How To Build/Buy It.
I have posted one version of that...
> * How To Use It.
Well, duhhhhh....
> * What To Expect From It.
I think my comments about low noise or the lack of it, follow under
this guideline.
>
> The 'target' "Reader" of the 'original' "Post" was the everyday
> Shortwave Listener { No License Required } .
And???? I guess that means you think all casual users of a device
should live in the dark, be fed clumps of shit, and be taught old
wive's tales... Right...
>
> Know Your Reader - Communicate Effectively - KISAP !
Know my reader? You must be kidding....I don't have *readers*....Or at
least, none of them have sent me a subscription yet...If you want me
to tailor my posts to a certain type of simple minded dumbass, you
will have to pay me.
> [ Keep It Simple And Practical ! ]
My PVC version can't get too much simplier...
>
> REMEMBER: What Works... WORKS ! { No Theory Required }
I'm sorry. I am not going through life as a crash test dummy....If you
want to, be my guest. Remember! I didn't write the *thesis* as he
called it. I just commented to the smartass that complained about it.
If you don't want to read something, no one is holding a gun to your
head. I find Telleys remarks about *censorship* on the shortwave NG to
be really offensive. It ain't *his* NG. After reading his last two
posts, I find *him* equally offensive. Only a childish asshole has to
make up names for people he can't agree with. I'm glad the goofy
bastard "plonked" me. He's obviously a smartass that wants to control
how other people think or act on *his* shortwave NG. That was not the
first time I'd seen him make smartass comments about RRAA for no good
reason either...I live on both groups, although I don't normally
crosspost, so I considered his comments to include me. MK
RHF
It's So Nice That We Are Communication ;-}
there is a 'trick' to that too ~ RHF
.
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= = = nm...@wt.net (Mark Keith) wrote in message
= = = news:<25eb70d7.04110...@posting.google.com>...