LOOP ANTENNA DISCUSSION

From:         Reg Edwards
Date:         1998/01/16
Subject:      Re: Loop Antenna Design Program?
Newsgroups:   rec.radio.amateur.antenna

Tim, you will find at my web site two, new, original, programs
dealing with single-turn loops from small magloops up to 3/4-wave
all the way round. Have been tested in practice. Used in a
"What-if ..... " mode.

Very simple access. Not zipped up. Download in 5 to 10 seconds
with one click. Can be put into use immediately. Will run on IBM
compatibles in DOS, or in a full-screen window from an icon.

Other free programs of interest to radio amateurs also available.
Click below. You can be using one in minutes.

Regards,  Reg,  G4FGQ
http://www.btinternet.com/~g4fgq.regp

=========================================================
Hero Electronics wrote ...
Does anybody have sharware program to automate the design of loop antennas?

=====
=====

Date: Fri, 03 Oct 1997 18:59:57 -0700
From: SHAWN AXELROD 
To: Gary Otteson 
Subject: Re: Kiwi Loop

Gary Otteson wrote:
}         I also find Mediumwave interesting. My question is, given my
} location, would the purchase of something like the Kiwi Mediumwave loop
} be to my advantage, or would the noise limitation of the city cancel out it's added potentials? It's a bit too expensive for blind experimenting.
 
}                                 Gary Otteson

Gary
I have seen the KIWA loop in action and it is very good. However i would
like to suggest a cheaper option or two. One is my four foot box loop
that I can supply you palns for on disk, on paper or go to:

 ftp://bbs.ks-huseby.no/html/loopant.zip.html

and down load the plans.

A also use a Radio Plus Electronics  Quantum Loop. This is a different
design as it is a ferrite loop but it is small. About 10 inches long and
about 8 inches in size. Its big advantage is $$$$. It is about half the
price and works almost as well. There is a review of this loop at:

 http://fly.hiwaay.net/~waholler/bcbinfo.htm

If you want more info write.
Shawn

-- 

REMEMBER ON A CLEAR DAY YOU CAN HEAR FOREVER
=====
This is the AM/FM/TV DX mailing list.
To post to the list, send an e-mail to :   amfmtvdx@qth.net
=====


Subject:      Re: loop anteneas better in citys?
From:          (Crabtreejr)
Date:         1997/09/08
Newsgroups:   rec.radio.shortwave

Daniel Grunberg   wrote on  8 Sep 1997 @
13:22:40 GMT
}
}
}Jim Nitchals writes:
}} In article ,
}} Toshiba 430CDT Notebook  wrote:
}}}Im curious, I live in NYC and have a very hard time getting HF dx
}}}stations, I have a wire antennea outside my windows (30') would using a
}}}loop be better why do people use loops instead of wire for HF listening?
}}
}} Your wire antenna is optimal along the axis it's aimed.  A loop antenna
}} can be pointed directly at a station for maximum signal strength, or
}} rotated to null (cancel out) interfering stations.  The Kiwa MW Loop has
}} two-axis nulling, which helps reduce AC interference too.  A single wire
}} antenna is more likely to pick up stray line noise.
}}
}} While I haven't had the luxury of building a long MW wire antenna, it's
}} the best strategy for extreme DX'ing.  At 30', your wire's far too short.
}}
}} In any urban area, a loop antenna's nulling abilities are terrific for
}} cancelling strong stations close to, or on top of the frequencies of
}} weaker ones.
}}
}
}Yes that's true for MW, but the question is being asked about HF, which I
}think means SW.
}
}As I recall, my old copy of the "Radio Amateurs Handbook" (American Radio
}Relay League, West Hartford, CT) say that loops aren't much use above the
}160 meter (approximately 1.9 MHz) amateur band.  I'm mot sure that that's
}still true, using modern techniques and core materials.  Perhaps someone
}who knows will answer that.
}
}The other part of the question  is whether a 30-foot (9-meter), outdoor
}antenna will work better, in the city, than a loop antenna located close
}to the receiver.  The SW receeption problem in the city has two roots.
}There are too many close-by households, with their electrically-noisy
}appliances and TV sets.  There are too many nearby (or perhaps
}surrounding) steel framed buildings acting to shield antennas from
}desired signals.
}
}IMHO, a 30-foot antenna that's in the clear and protected from picking up
}noise probably will do better than an indoor loop which may be shielded
}and mostlikely will be surrounded by noise sources.  If you want to try
}something, you might look at John Doty's method of keeping your
}antenna's lead-in from picking up noise (see "So You've Decided You
}Need an Outdoor Antenna" on my web page) or you might want to augment
}your outdoor antenna with a noise-cancelling-antenna device (MFJ has one).
}
}
}
}--
}Daniel A. Grunberg              Kensington, Maryland  USA
}
}My home page's URL is  http://www.nyx.net/~dgrunber/
}
Loop antennae are now used by hams in all bands from 1.6-30MHz.  There are
commercial products available from AEA and MFJ, which can also be used for
transmitting.  For reception only, you can build a loop fairly easily.
Bigger is better, as the Q of loop antennae is very high, and gets higher
as the loop gets smaller and/or the frequency gets smaller.

You might want to check out the following articles at your local library:
1.  Small loop design for HF QRP, Jay Jeffery, 73 Amateur Radio Today,
April 1997,
      pp 42-43
         a very straightforward article with some simple inductance equations
2. An update on compact transmitting loops, QST, Nov 1993, pp37-40
       has a comparison of sizes and ranges of commercial products, shows
details of
       a coupling loop with a Faraday shield, and useful graphs of gain vs
frequency,
       and bandwidth vs. frequency for different size loops.
3. You can build: A compact loop antenna for 30 through 12 meters, Robert
Capon,
     QST, May 1994, pp 33-36
        a constructional article, for a single turn loop 2' 7'', dia with
a coupling coil.  If
        you get a copy, make sure that the picture on the first page is
legible.
4. The MFJ-1786 High-Q loop Antenna for 10-30MHz, Rick Kleinschmidt,
      QST, Aug 1994, pp 62-64
         a favorable product review

You may also be able to find these articles:
5. Indoor loop aerial for short waves, S. Mukherjee, Electronics and
Wireless World,
       April 1985, pp38-39.
            this article shows a system using a coupling loop.  Both loops
are made
            from coax cable and are shielded.  It gives the following
dimensions
            4-9 MHz, main loop 700mm dia, coupling loop, 140mm, tuning cap
500pf
            8-18 MHz, main loop 440mm dia, coupling loop, 105mm, tuning
cap 200pf
            18-26 MHz, main loop 350mm dia, coupling loop, 80mm, tuning
cap 100pf
             excellent constructional picture
6. Short wave loop aerial, G. Wareham, Electronics and Wireless World,
       Feb 1986, pp41-42.
            this is a design for domestic receivers
7. The box loop, G.W. Short and V. Smith, Electronics and Wireless World,
       June 1987, pp637-638.
             a very low cost design for reducing the effects of
mains-borne interference
             for SW listening

To reduce noise pick-up, you would probably be better off using the design
shown in Mukherjee's article.   My gut feel is that his loops are small for
the frequency ranges to be covered,  given the graphs in (2).  I am
thinking about building a shielded  loop about 4 feet in diameter.  I am
interested in the range of 6-18MHz. The main loop will be made from RG/8
coax, to keep the resistance losses small

I have a longer list of references to loop antennae, which I will post if
there is interest.

John Crabtree
crabtreejr
======
======
                                      
Subject:      Re: Calculate large loop inductance ??
From:         Tony Maher 
Date:         1997/08/15
Newsgroups:   sci.electronics.design

Jim Thompson wrote:
}
} I'm trying to pep up an AM radio in a poor reception area, and
} long-wire antennas are not allowed by the home-owner's association.  I
} am considering a large loop antenna in the attic, possibly 2 feet in
} diameter.  Are there any equations floating around for how to
} calculate the inductance of such a loop??  TIA!
}
}                                         ...Jim Thompson

Jim,
        For about 15 years I have used a 1 metre length of 20 way computer
ribbon, series connected to form a coil, and connected to a 300pf
variable capacitor as a very portable antenna for use when travelling.

The whole thing rolls up into a small space and when needed is unrolled
and formed into something approximating a loop which is hung over as
suitable book, bible or whatever.
The radio is then placed almost within the loop, with its length at
right angles to the plane of the loop.

Tuning is sharp, and the performance of the radio is vastly improved.
Rotating the loop helps to get rid of noise sources commonly found in
hotels motels etc.

Tony Maher
======
======
                                      
Subject:      Re: Calculate large loop inductance ??
From:         Tom Woolner 
Date:         1997/08/14
Newsgroups:   sci.electronics.design

In article <33f53525.5001734@news.primenet.com>, Jim Thompson
 writes
}I'm trying to pep up an AM radio in a poor reception area, and
}long-wire antennas are not allowed by the home-owner's association.  I
}am considering a large loop antenna in the attic, possibly 2 feet in
}diameter.  Are there any equations floating around for how to
}calculate the inductance of such a loop??  TIA!
}

I have had good results from a so-called H-multiplier arrangement.  This
consists of a large-area coil, tuned with a 300pF radio tuning
capacitor.  I seem to remember it had about 12 turns and an area of
about 4 sq. ft. (square with 2 ft side).  Tuning was quite sharp and had
to be re-adjusted for each station tuned on the radio.  The coil was
stood up with its plane vertical and the radio was placed inside the
loop.

I had marked improvements in seeking out the low power European stations
from here in England, when I was interested in such things.  Being
directional, I could sometimes nul-out interfering signals on the same
or close frequencies by swinging the plane of the coil about a vertical
axis.

No connection to the radio is needed as it works by concentrating the H-
field in the neighbourhood of the ferrite rod inside the set.

Regards,
--
Tom Woolner
======
======
                                      
Subject:      Re: MW antenna
From:         (Jim Nitchals)
Date:         1997/07/23
Newsgroups:   rec.radio.shortwave

In article ,
ryan cleveland wrote:
}
}I have a Drake SW8. I'm looking for the best MW antenna. The only one I
}can find is the Kiwa MW Air-core Loop Antenna.

If you have a thousand feet or more of linear outdoor space to work with
a long wire antenna ("beverage" type) is supposed to be the best  :)

As far as compact antennas go, I have a Kiwa loop and a Drake R8A and
absolutely love the combination.  A few web sites mention the Quantum
loop edging out the Kiwa in a few situations, and the Quantum loop is
less expensive.  Overall, the reviews lean in Kiwa's favor if money
isn't a major concern and you ONLY care about MW reception.

The folks who answer the phone at Kiwa are extremely helpful and
technically competent.  Their MW loop has brought countless pleasant
hours of MW listening and I recommend it highly.  If there's a better
commercial MW antenna, it hasn't been mentioned in news or on the web.

--
Jim Nitchals                                      
======
======
                                      
Subject:      Re: LOOP Antenna  for 20 meters?
From:         Joe BV/N0IAT 
Date:         1997/06/12
Newsgroups:   rec.radio.amateur.antenna

Hi Bob,
You might check the ARRL web page at
 http://www.arrl.org

I recall they now have a QST index that
dates to the 1920's -- try searching the
index for loop antennas and see what comes
up.

For sanity's sake, I recall the same article,
and I think it was 1994 or 1995 -- it was a
2-part article and the author built a low power
unit in part 1 and higher power unit in part 2.
The key was the capacitor he built, using mylar
insulation if I recall.

Good luck
Joe BV/N0IAT
======
======
                                      
Subject:      Re: MW Antennas
From:         Ron Hardin 
Date:         1997/05/30
Newsgroups:   rec.radio.shortwave

Digitup wrote:
}
}    My Select-a-Tenna is supposed to arrive via mail today. I'm hoping it
} will be a nice complement to my new Superadio. But I can't help being
} intrigued by the talk of big frame/loop antennas people talk about here.
} Instead of instructions i dont understand, somebody MAKE me one !  And
} if that is out of the question, let me ask this:
}    What would happen if you made a giant crossbeam, wrapped however many
} rotations of wire around it, then attached one end to the ground, the
} other to the am antenna. nothing fancier than that.. I suppose I could
} even build it in such a way that I could rotate it four directions
} instead of only two. Would this improve reception ?
}    Also, are there any good Medium Wave antennas avail. at Radio Shack >
} (The idiots friend)

I built an 18" square tuned loop (14 turns), a 32" square tuned loop (10 turns)
,
and a 6 foot tuned loop (now cut and reused), and found the small ones
worked as well as the larger ones.

Moreover the larger ones are harder to tune, I mean have less of a frequency ra nge with
a standard broadcast band variable capacitor, I think because of their increase d
stray capacitance.   So now I have more small ones around the house, having cho pped
up the larger ones to make them.

I don't know what theory ought to apply; perhaps the coupling to the radio goes
down a the loop gets bigger; or perhaps it all could be considered a matching
problem with best match at small sizes.  In any case, once you hear the backgro und
noise quite loudly, you're raising the noise as much as the signal even if you
were to find a better match.

The improvement with a MW loop is spectacular during the day, in any case.

At night, there's so much signal available that the loop doesn't help any;
in fact it's hard to tell at night that it's working.
--
Ron Hardin

On the internet, nobody knows you're a jerk.
======
======
Subject:      Re: am broadcast loop antennas
From:         Madjid 
Date:         1996/11/29
Newsgroups:   rec.radio.amateur.antenna

Paul Giusti [VK3FPG] wrote:
}
} I have been looking with no success for some plans or constructional
} information for a broadcast band (500-1700khz) loop antenna and am
} hoping someone out there may be in a position to e- mail me some plans
} or direct me to a web resource that has this information available.

Check the Nordic Page they have a lot of stuff on AM antennas

      http://sds.se/org/swl/

There is also Radio Netherland

      http://www.rnw.nl/en/pub/

-------------------
Madjid, VE2GMI - Home Page:  http://www.CAM.ORG/~mboukri
NEC4WIN Antenna simulation for Windows
======
======
                                      
Subject:      Re: Calculate large loop inductance ??
From:         Brooke 
Date:         1997/08/14
Newsgroups:   sci.electronics.design

Jim Thompson wrote:
}
} I'm trying to pep up an AM radio in a poor reception area, and
} long-wire antennas are not allowed by the home-owner's association.

Jim:

Have a look at:  http://www.ccrane.com/selectar.htm

I think either this version, or one of the other tuned loop antennas
that are carried by C Crane is what you are looking for.

Brooke
======
======
                                      
Subject:      Loop Antennas for AM and SW
From:         "John S. Seybold" 
Date:         1997/06/10
Newsgroups:   rec.antiques.radio+phono

I have just acquired an Admiral 53-K6 wooden tabletop radio that is
missing its back and antenna.  The antenna wires are from the chassis
and the antenna transformer.  Does anyone have any ideas on how I should
wind a loop antenna that would be suitable for both AM and SW?  I have
no idea how much wire to use or if there are any shaping
considerations.  Thanks.

John S. Seybold
Orlando, FL

jseybold at gdi dot net
======
======
                                      
Subject:      Re: Loop Antennas for AM and SW
From:         Rod Rogers 
Date:         1997/06/10
Newsgroups:   rec.antiques.radio+phono

Most loop antennas were about 20 turns. Dimensions are not critical,
just make it fit the new back, abt 4" x 7", or so. Be sure to do a
complete RF alignment when done, or at least peak the antenna section of
the tuning gang. This is the larger of the two sections, and you tune
the small screw adjustment for max signal at abt 1400 KC. Use very small
wire, or it will become a BEAST!

-------------<(O)>-------------
  Rod Rogers,  Salina, Kansas
          Home Pages:
  http://www.tri.net/flywheel/
   http://www.tri.net/radio/
-------------<(O)>-------------
======
======
                                      
Subject:      Re: Loop Antennas
From:         "E. W. Balinski"
Date:         1997/04/26
Newsgroups:   rec.radio.shortwave

VANK6 wrote:
}
}     Can anyone suggest a source of information on the subject of Loop
} antennas for SW listening,particularly the design and construction
} details.Any information greatly appreciated.

Check the ARRL Antenna book of the current issue.  I think the
18 edition just hit the streets.  They have design information
as well as a few construction articles. The book is available
at your local ham radio store, via the 800 #s (HRO), or
from the league directly 860-666-1541

The articles are biased more towards the ham bands but they are
certainly easy to redesign to the SW bands.  Equations are
included.

GL
73
Gene  K1NR/3
======
======
                                      
Subject:      Re: Loop Antennas
From:         Dennis Ingebretsen 
Date:         1997/04/27
Newsgroups:   rec.radio.shortwave

VANK6 wrote:
}
}     Can anyone suggest a source of information on the subject of Loop
} antennas for SW listening,particularly the design and construction
} details.Any information greatly appreciated.

"Joe Carr's Receiving Antenna Handbook" which I just bought at Ham Radio
Outlet has an entire section on the theory and home construction of
small receiving loop antennas. I am currently building one of the
designs myself, and highly recommend the book.

73's   Dennis  (N6TUQ)
======
======
                                      
Subject:      Re: Loop Antennas
From:         robert bowman 
Date:         1997/04/26
Newsgroups:   rec.radio.shortwave

VANK6 wrote:
}
}     Can anyone suggest a source of information on the subject of Loop
} antennas for SW listening,particularly the design and construction
} details.Any information greatly appreciated.

the National Radio Club has a raft of material devoted to loops. they are
geared to MW reception, but the principle remains the same for any
frequency.
======
======
                                      
Subject:      Re: AM Loop antenna
From:         Harry Lythall
Date:         1997/07/09
Newsgroups:   rec.radio.shortwave

GERYS wrote:
}
} Is there a good ( and inexpensive) Am loop antenna I can buy or build.
} Palomar and Kiwa too steep for me. Advice?
} Thanks.

4 - 8 turns of 'thick' wire on a 1 meter square wooden frame. Put a
250pF variable across the end and put the radio inthe middle. Works
a treat.  If you need an electrical connection - 1 turn loop in the
center is about right for 50 ohms.

See a picture of a 3.5 MHz version under ANTENNAS on my homepage-
 http://user.tninet.se/~acz732k/ 
======
======
                                      
Subject:      Re: small loop antennas
From:         pmarkham
Date:         1997/05/31
Newsgroups:   rec.radio.amateur.antenna

In article <338FA638.560F@mobynet.com>, bryan says...
}
}I am interested in putting up a small loop antenna for 75m and would
}like to see a few comments on size, dbd, directivity, ect. Try as I
}might I have been unable to find any specific url's on the design of
}this type of antenna. Can someone point me in the right direction?
}                                  -73  Bryan  wa6hdh


  A program I found useful is MLOOP, by Hans Joachim Kromer,
DK1NB @ DB0TCP.#HES.DEU.EU

  I located and retrieved my copy from ftp.funet.fi in something
like the pub/ham/antenna directory. It gave me a real introduction
to small antenna losses and the various factors that influence those
losses due to design limitations. Not pretty, but functional, with
documentation. I am not shy about referring it.

  "The program MLOOP v 3.1 is designed to aid construction of
magnetic antennas for frequencies from 1 to 60 MHz.
You can choose by installation the language german or english.
It runs under DOS, Windows and DOS-window of Windows 95,
Windows NT and OS/2.

 The calculation of round, quadratic and octogonal loops is
possible. The output is provided in three columns.
Different materials, forms, loop diameters, pipe diameters,
frequencies and power ratings may be entered. The Q-factor and
bandwidth are modified to provide values as they occur in
practice. Loading and saving of the parameters as well as a
hardcopy is possible. You can calculate also qualified
capacitors for the loop. In the helplines you have 3 pictures
which show the design of the loop, the link-loop and the
construction of the pipe-capacitor......"

                 Pete/wa4hei
======
======
                                      
Subject:      Re: right wire for antenna
From:         (bowman)
Date:         1997/04/18
Newsgroups:   rec.radio.shortwave

In article , egil.hjelmervik@
filosofi.uio.no (Egil Hjelmervik) says:
}
}Does anybody have any experience with types of wire for home-made MW loop
}antennas?

for receiving antennas, any wire that is mechanically strong enough for the ant
enna
design is fine. i tend to use 14 awg TFFN house wire since it is inexpensive an
d
readily available. this is real overkill, however.
======
======

                                       
From:  (Adam Trent Phillips)
Date: 3 Mar 1997 11:19:44 GMT
Newsgroups: rec.radio.shortwave


        I know that I have been saying I was going to post some of this
stuff, so for once and for all, here it is......



    The following was taken from "The Low and Medium frequency radio scrap
book". It was written by Ken Cornell (W2IMB) and published by Ham Radio
magazine. (C) Communications Technology, Inc. 1977

    The following is on page 47-


"The following table gives the inductance and frequency range of square
loop antennas that are 12" , 24" and 36" on a side. Wire spacing for 1/4"
and 1/2"....* Other size frames and wire size spacing can be determined
by interpolation....* The frequency range shown, is based on using a
variable capacitor of 500pf."


[*:these four periods where in the original text - ATP]


    "L" is the inductance in microhenries


# of  |   12" square      |   24" square      |    36" square    |
turns |-----|-------------|-----|-------------|-----|------------|
      |     |     KHz     |     |     KHz     |     |   KHz      |
      |  L  | max. |  min.|  L  |max.  | min. |  L  |max.  | min.|
------|-----|------|------|-----|------|------|-----|------|-----|
  4   |  13 | 6240 | 1978 |  32 | 3980 | 1260 |  52 | 3120 | 988 | 1/4 "
  8   |  41 | 3510 | 1112 | 103 | 2215 |  703 | 173 | 1710 | 542 |
 12   |  78 | 2546 |  807 | 203 | 1576 |  500 | 346 | 1210 | 383 | spacing
 16   | 131 | 1968 |  623 | 323 | 1252 |  397 | 559 |  952 | 301 |
 20   | 168 | 1736 |  550 | 462 | 1047 |  332 | 809 |  792 | 250 |
------|-----|------|------|-----|------|------|-----|------|-----|---------
  4   |  11 | 6780 | 2150 |  28 | 4260 | 1347 |  46 | 3315 | 1050|  1/2"
  8   |  32 | 3980 | 1260 |  85 | 2440 |  773 | 145 | 1816 | 592 |
 12   |  57 | 2980 |  943 | 161 | 1773 |  562 | 281 | 1343 | 426 | spacing
 16   |  86 | 2425 |  768 | 245 | 1437 |  456 | 439 | 1072 | 340 |
 20   | 113 | 2120 |  672 | 342 | 1218 |  386 | 625 |  901 | 284 |
------|-----|------|------|-----|------|------|-----|------|-----|---------



    As you can see, you can use the formula for self inductance, by
translating the square into a circle (ie: the length of all four sides
equaling the diameter).



    First, find the mean radius.


              A=(Len * 4) / PI / 2

    A= the mean radius
  Len= the length of one side of the square
   PI= 3.141


    Then use it to find the inductance of the coil.


          (N * A)^2
     L= ---------------
          9A + 10B

    L= inductance in micro Henrys
    N= the number of turns
   PI= 3.141
    A= is the mean radius in inches
    B= the Length of the coil, in inches (not WIDTH !. Two turns at two
                                          turns per inch = 1 inch !)




The antenna will resonate at :


                      1
             ____________________
       Fo =               /-----
               2 * pi * \/ LC


    Fo= resonant Frequency in Hertz
   PI = 3.141
    L = inductance in henrys
    C = capacitance in farads


    Now before anyone writes back angry, I know that there is a small error
in the formula to convert the mean radius. I guessed at a formula that
seemed to do the job within a reasonable margin (compared to the chart. the
formula was about 8% accurate if I remember right). If someone has a better
formula to calculate the inductance of a square coil, please post it and
Email it to me.The formula I use was intended for round coils. I do feel,
however, that the formulas given here are close enough for experimental use.

    If your radio has a low Z input, you will have to match the impedance.
a single, smaller turn in the center (coupling will have to be done by
experimentation) will match the impedance. An LC circuit could also be
used,as it is in may transmatches, but I'll save that for a later post,
since I am already long winded enough.

    In this book on LW & MW, I noticed the author used a lot of receivers
that had the antenna directly connected to the receiver input. A lot of AM
Dxers tend to use their loop antennas inductively couple to the radio's
loopstick(loop) antenna. I got a hunch that this will allow a nice match
for impedance.I also strongly recommend getting a copy of this book.


   I plan to put one together for 160-190 KHz experimental LW band along
with one for AMBC and lower Shortwave (to 5 MHz I guess...I still have to
do the math)




PS: to readers outside of the USA; I'm sorry that I did not have a chance
to convert this into metric for you, I just didn't have the time.


=====
=====
                                       
From: cdkolyer
Date: Sun, 02 Mar 1997 19:33:13 -0600
Newsgroups: rec.radio.shortwave

  "Jeffrey Donohue"  wrote:
}
} I have read several posts here concerning the use of a "loop antenna" for
} MW DXing.
}
} I am under the impression thay it does not connect to a radio, but just
} sits near one... is this true?
}
} Can someone please explain exactly what this is and how to make one?
}

This is an additional response- please see my other response.

Others have built loop antennas (antennae) for am (mw) that are half a
meter (about 20 inches) on the side square loops, with 14 or 15 turns of
wire. This may be more appealing to those with limited space. The
operating principle is the same. My second loop is 17 turns wound on a 16
inch diameter cardboard tube- a cable spool- and with a capacitor from a
sony clock radio, tunes from 600 to about 1200 kHz.  I have an
extra/optional connection at 12 turns for upper frequencies. So... 14
turns on a 20 inch by 20 inch square ought to work IMO. Some people wrap
an isolated turn around the center of the loop; this is called a pick-up
turn, and is connected to ANT and GND (antenna and ground) on the
receiver. Others connect the ends to a simple FET (or JFET) pre-amp, the
output of which is connected to ANT and GND of the receiver. If you own a
receiver without external antenna/ground hookups, then placing the radio
next to the antenna (inductive coupling) is your best bet, and should
give good results- no miracles, just a boost in signal strength. I have
appreciated the results from my loop more in the daytime than at night. I
like my smaller loop (16 inch diameter) more than the 1 meter loop
because its easier to move about. Good luck with your AM antenna
building!

-------------------==== Posted via Deja News ====-----------------------
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=====
=====
From: cdkolyer
Date: Sun, 02 Mar 1997 11:33:03 -0600
Newsgroups: rec.radio.shortwave

  "Jeffrey Donohue" wrote:
}
} I have read several posts here concerning the use of a "loop antenna" for
} MW DXing.
}
} I am under the impression thay it does not connect to a radio, but just
} sits near one... is this true?
}
} Can someone please explain exactly what this is and how to make one?

I've built a few.  Buy a radio at a Garage sale and remove its tuning
capacitor.  Nail and Elmer's Glue together a square made of 1 by 4s that
is one meter (39.5 inches) long on each side. Add cross braces at the
corners for support.  Wrap this frame neatly with at least 7, but no more
than 10, turns of 22 gauge insulated solid wire (stranded wire works
too.) Heaver gauges work to, but usually cost more. The number of turns,
in conjunction with your tuning capacitor, determines the tunable
frequency of the loop. I'd recommend 9 turns. Space the turns out from
each other by 1/4 inch to 3/8 inch. This forms a parallel LC circuit (see
your Physics textbook) Put your radio in or near the loop.  You'll tune
the loop with its tuning cap, and also point it at the direction of the
signal source-the city you are listening to.  The loop works through
"inductive coupling" to your radio's internal ferrite bar/loop antenna.
Do a keyword search on the web for AM MW LOOP ANTENNA. Good Luck.

P.S. I wasted $$$ on National Radio Club's Antenna Reference Manual, Vol.
One. It won't teach you anything more than what you can find on the
web/this usegroup.

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=====
=====
From: Werner Funkenhauser
Date: 10 Feb 1997 00:04:10 GMT
Newsgroups: rec.radio.shortwave

H. Caron wrote:
} Any trick of the trade someone could suggest?
} Could Kiwa loop acheived it? Any other loop? (just curious!)
  ^^^^^^^^^^^^^^^^^^^^^^^^^^^
}
} Thanks in any case and have fun,
}
} H.C.

Thanks for the post H.C. The "real cardboard box" loop you described has
appeared in hints-and-tips type columns over the years. I've built a
couple of them myself for short-term use.

To answer your question, yes! The Kiwa could achieve it in spades. I've
been using, building, and buying mediumwave loops since 1958. In my own
experiences, aside from a 3000-5000 foot Beverage antenna pointed right
at the DX, the Kiwa is the closest to ideal. Its got it all --- gain,
balance and sheer ease of use. However well-known NRC DXer, Mark
Connelly (an experienced NRC DXer) compared it to Moore's passive loop
and actually gave the Moore better marks in some respects. That's so you
know I'm not looking at the Kiwa through rose coloured glasses. :)
However, until I use Moore's product, I'll stick by my original
statement.

For information about the Kiwa loops performance, check my Proceedings
Review and that of others' at:

                                http://www.wolfe.net/~kiwa/review.html

As for the great inductively coupled loop discussion, basic theory is
that if you're looking for maximum signal transfer no matter the design
(ferrite loop or air-wound), the wires in both coils should be parallel
and properly coupled (a relative term). Hence, in the case of a ferrite
loop, the rod should be at right angles to the inductive loop since the
windings go around the rod. The article's writer, Pete Haas used a small
air core loop and found that when the planes of the antennae were the
same, he had maximume signal transfer. The wires were after all,
parallel in both antennas. Another user having a different receiver
might have needed to couple the receiver and antenna differently and
that's why I suggested experimenting with other angles (perhaps I should
have added positions with respect to distance, also!!). A receiver hung
with its ferrite loop dead centre inside a perfectly balanced air-core
loop, would probably be the optimal setup as suggested by Daniel and
Larry. They're probably correct if the only concern is is maximum signal
transfer in ideal conditions (e.g. the QRM is near right angles to the
DX) without other QRM considerations, nor null distortion of any kind.
But that's not real life in the DX world.

I logged HRNN21 San Pedro Sula (Honduras) on 770.6 kHz with both WABC
New York and HJJX Bogota audible on 770 kHz by using a Kiwa and Icom
R71A equipped with an Eskab/Edvis PLAM. I used a modified Gerry Thomas
2.3 kHz filter) DX400 which I placed inside the frame of my 1 metre box
loop. I might add, the DX400 radio (thus its ferrite rod) was eventually
placed 30 degrees away from parallel to windings on the box loop (quite
contrary to theory) and the box loop was pointing at 180 degrees --
almost directly at the Colombian. Nothing by the book, that's just how I
got maximum signal indication. The DX400 could unfortunately only detect
the Honduran carrier with BFO zero-beat (while I had identifiable audio
and several clear IDs with my venerable Icom). When I "correctly" aimed
both DX400 receiver and antenna to about 180 degrees there was almost no
indication of signal on 770.6 kHz, and lots of QRM from a strong HJJX
and a lesser WABC. The effect of the DX400 being a full 60 degrees away
from ideal placement was to cause some sort of phase reversal or
distortion in the 770 kHz QRM.
The "phasing" phenomenon is well documented and is used by at least one
commercially produced ham antenna manufacturer, not to mention
mediumwave DXers (some of whom use Mark Connelly's designs) to reduce
QRM to loops by means of longwires or other loop antennas. I myself have
a Connelly loop versus longwire phasing unit which I used with my one
metre loop in the past. However, since owning a Kiwa, I never use the
combination anymore.

Theory is a good starting point but then you use what's practical and
what works.
--
Regards,
Werner Funkenhauser
WHAMLOG links:  http://www.inforamp.net/~funk

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