I screwed up the first post of this message! Please forgive me <:(
Anyway, I can't get a direct link going to the photo section from
within a message. I had a good number of replies to my posting of the
Magloop antenna I am in the process of building. Most notable is the
confusion of the rotor of the Butterfly capacitor. Almost all
variable capacitors have a sliding contact on the rotor to provide a
link to the rotor vanes. This sliding link is the cause of a lot of
loss through the capacitor. A Butterfly capacitor eliminates this
loss, as no contacts with the rotor vanes are required. This type of
capacitor is really 2 capacitors linked via the rotor vanes on each
side if it. The rotor shaft material is not required to be conductive
nor any contact to it to be made at all. You could make the shaft
from fiberglass, which would actually be best! However, this would
make construction difficult. The stator vanes on each side must be
insulated from each other and the capacitance is across the rotor
from one set of stator vanes to the other set of stator vanes on the
other side. There are no mechanical contacts across this capacitor
and using copper has the advantage of a higher conductive material
than aluminum and is very easy to cut by hand with aviation snips.
Also, silver plating may be applied directly to the copper material
for even less loss. Check this site for an easy way to homebrew
silver-plating.

The only problem I have encountered is the availability of copper
threaded rod and copper nuts. These items are extremity expensive! I
used steel all-thread 1/4-20 rod and matching steel nuts. I also
soldered copper strips from the scrap made when cutting the rotor and
stator vanes. This prevents the loss from trying to use the steel
hardware as a conductor. Each stack of stator vanes have a 1/4 inch
wire copper strap soldered across them and extra length for
connecting each side to the loop element. I may copper plate the
steel hardware later and then silver plate over the copper. I don't
really like the idea of having steel anywhere around a Magnetic loop
but I will just see how it performs. The drawing and pictures are in
the photo section in the Butterfly folder. Just click of the folder
to bring them up. The drawing shows metric measurements being used.
Exact size is not required but I would not make the capacitor any
smaller due to the requirement of using 1/4-inch or 6 MM hardware.
Bigger is better! Just keep the shapes the same and proportions equal
between the rotor and stator vanes. When the rotor is completely
unmeshed from the stator vanes the capacitor should appear to be a
circle except for the very slight 1.4 mm gap to keep distributed
capacitance to a minimum and allow the lowest capacitance possible
when unmeshed. I hope this clears up any confusion!

BRIAN,

Low Noise Receive "Only" Coax Cable Loop Antennas for
160 Meter to 10 Meter HF Shortwave Bands -by GreerTech


I built one of these Coax Cable [Shielded] Loop Antennas for
the 60 Meter Shortwave Band; my intended Lowest Frequency:

- 4.75 MHz to 5.06 MHz with a MidPoint of 4.905 MHz
- Cut to 13.5 Feet [1/10WL] VF=0.66 using RG8 Coax Cable.
- Square shape 3.4 Feet per Side with 4.8 Cross-Arms.
- Round shape 4.3 Diameter Circle.
- Coax Cable Lead-in-Line 5 Feet.

This Coax Cable [Shielded] Loop Antenna is very 'quiet' and
work very well if you are limited to an InDoor Antenna ONLY.

I tried using a Tuner {Pre-Selector} with it; but with my
Icom IC-R75 and Kenwood R-5000 Receivers the Tuner proved
to be un-necessary.

* The Coax Cable [Shielded] Loop Antenna can be used to
NULL-OUT 'local' RFI/EMF man made Noise within the house.

* For the Shortwave Band Frequencies above 5 MHz to 25 MHz
the Coax Cable [Shielded] Loop is an NON Directional Antenna.

* For the AM/MW Broadcast Band (530 kHz to 1700 kHz) it becomes
a Directional Antenna and the use of a Tuner {Pre-Selector} helps.

TIP: I used some 5/8" or 3/4" (White) Low Pressure Water Line
Polyethylene Tubing as a "Form" to hold the Loop in a Circle Shape.
Sort of like a Big Hula Hoop. Build your Loop and just before
you are ready to assemble at the bottom; slide the Coax through
the Polyethylene Tubing. Cut the Polyethylene Tubing so that it
is about 2" shorter than the Circumference of the Coax: This is
to leave 'room' to make the Bottom "Joint" to Complete the Loop.
Shape-Out the Polyethylene Tubing so that it is a Circular Loop.
Finally make the Bottom Coax Shield {Connection} Joint.

FWIW: Sometimes when using this Loop with the Icom IC-R75,
I will have a clear and listenable Signal with NO 'apparent'
S-Meter Reading. The Signal is so quiet that I can use the
#2 Pre Amp and still have a Cleaner and More Listenable Signal
then by using my 75 Foot Low Noise Inverted "L" Antenna. The
Inverted "L" will have an S-7 to S-9+10dB S-Meter Reading, but
the background noise level will be S-2 to S-4 and a small
amount of noise can be heard with the program audio.

SUMMARY: An "Easy-to-Make" Coax [Shielded] Loop Antenna.
A very good Antenna for SWLs with Noise Problems and who
are 'limited' to InDoor Antennas ONLY. Makes a nice Second
Antenna for dealing with some types of Reception Problems.
NOTE: I would make my next one with RG58 or Mini RG8.

RECOMMENDATION: If you are going to use one of these Coax
[Shielded] Loop Antennas InDoors with an OutSide Antenna with
a single Radio/Receiver. Buy a 'quality' Antenna Switch like
the MFJ-1702C; Alpha Delta 2; Daiwa CS-201 and others.




These will allow you to 'switch' between Antennas; and they
automatically "Ground-Out" the Un-Used Antenna. Also these
Antenna Switches have a "Center" position that "Disconnects
and Grounds both the Antennas when the Radio/Receiver is
not-in-use. {A Nice Safety Feature.}


iane ~ RHF
.
.
= = = "Brian" <imaginaryfriend@wh*tth*f*ck.c*m> wrote in message
= = = news:<U0Ged.6046$5i5.5787@...>...

Anyone familiar with this particular antenna ?
Have you had success ?
Is it necessary to use an antenna tuner ?
Just curious.

-Brian

.

I just uploaded some pictures to Photos section of this group. the
direct link is.....


&.dir=/Butterfly&.src=gr&.view=t&.url=http%
3a//us.f1.yahoofs.com/groups/g_12851910/Butterfly/Stator.gif%
3fbc4RgewBlMGUkPnX&.cx=150&.cy=91&.type=u

These pictures and drawings show how to make a transmitting Butterfly
capacitor. Nuts and all-thread are used as spacers and to hold it all
together. Metric size is shown but you can make the parts any size
you like as long as you keep the shapes correct.

开云体育

----- Original Message -----

From: Michael Hebert

To: loopantennas@...

Sent: Sunday, October 24, 2004 1:06 AM

Subject: [loopantennas] Re: Preamplifier

>>>I wouldn't recommend a Ramsey kit to anyone. Their components are the
cheapest possible grade<<<<

You've got it! I purchased their AA7 several years ago with their enclosure. I guess the amp did a fair job but?I wouldn't have given fifty cents for the $15 enclosure if I had seen before?I ordered it.

I would advise anyone who thinks they have to try the AA7, don't buy the enclosure build your own or fit it to a Bud box. RM~

?

PS, If anyone is still not convinced, I'll make you a real deal (absolutely no guarantees)?on a hardly used?AA7 complete with factory enclosure. :(

Hello to all,

Thanks for all how replied.

Did somebody try using the R.F. AMPLIFER KIT on Ocean State Electronics
( ) ?

they say :" A small circuit, using the Mar-6 Amplifier IC, this kit
will provide? as much as 20 db gain.
Connect at receiving antenna input; will?boost signals from 1 mhz to
1000mHz; two RF amplifier kits may
be cascaded for use at low, broadcast-band frequencies. Use
with?Scanners, Ham recievers, SWL reciever etc.
You could add a metal?case and RF connectors for permanent use. May be
used to boost signal for scope or frequency
counter as well"

73,

Niki

John,

I wouldn't recommend a Ramsey kit to anyone. Their components are the
cheapest possible grade, the circuitry uses minimal bypassing and
decoupling and board quality very poor. You can buy good quality
components and build your own properly performing unit for less than
the cost of a Ramsey kit.

I've been burnt by their shoddy products too often and will never buy
another one.

73,

'Bear' NH7SR

--- In loopantennas@..., SG2112@y... wrote:

Ramsey sells a kit that should work, you can order direct or from

one

of the several electronics suppliers that carry their products ...


preadd=action&key=AA7C

You can look at the manual here, unfortunately the schematic has

been

redacted ....



John

--- In loopantennas@..., "N.Kantor" <nkantor@m...>

wrote:

Hello All,

I' have built a shielded loop for SW (1M diameter) which works

very

nice.

Now I want to build a preamplifier for that antenna.

I have found a scheme for an amplifier on the Net by Lyle

Koehler -

As I live on a boat and there no electronic shop within 500 km

from

where I live, I wonder if any of you know if it is possible to

order a

kit
for that amplifier on the Net ( or any other preamplifier which

is

similar to Lyle's ).

Any advice ?

73

Niki

Niki,

The parts should be available from Mouser Electronics, Digikey, Ocean
State Electronics, Dan's Small Parts and a number of other sources.
Ocean State's online catalog is probably the easiest to navigate.

73,

'Bear' NH7SR

--- In loopantennas@..., "N.Kantor" <nkantor@m...> wrote:

Bear and Scott (and all),

Thanks for prompt reply :).

Michael, Could you please recommend one or two of these "mail-order
sources", ones which you know.

I still prefer to wait and see if someone can recommend a kit, if

not,

i'll take Bear's advice.

Thanks and 73,

Niki

开云体育

Uh... we are all on the Loopantennas list already. ;')

Steve

--- Scott Erwin <n4zou@...> wrote:

You might want to check out the loopantennas yahoo
group.

=====
Steve Greenfield // Digital photography, scanning,
Polymorph Digital Photography // retouching, and photomorphing
253-318-2473 voice // to your specs.
polymorph@... //
// Based in Tacoma, WA, USA

Bear and Scott (and all),

Thanks for prompt reply :).

Michael, Could you please recommend one or two of these "mail-order sources", ones which you know.

I still prefer to wait and see if someone can recommend a kit, if not, i'll take Bear's advice.

Thanks and 73,

Niki

Ramsey sells a kit that should work, you can order direct or from one
of the several electronics suppliers that carry their products ...


preadd=action&key=AA7C

You can look at the manual here, unfortunately the schematic has been
redacted ....



John

--- In loopantennas@..., "N.Kantor" <nkantor@m...> wrote:

Hello All,

I' have built a shielded loop for SW (1M diameter) which works very
nice.

Now I want to build a preamplifier for that antenna.

I have found a scheme for an amplifier on the Net by Lyle Koehler -

As I live on a boat and there no electronic shop within 500 km from
where I live, I wonder if any of you know if it is possible to

order a

kit
for that amplifier on the Net ( or any other preamplifier which is
similar to Lyle's ).

Any advice ?

73

Niki

Niki,

Lyle Koehler's preamp works very well but I don't know of any source
of a kit for it. The parts are all relatively common and should be
available from any number of mail-order sources.

73,

'Bear' NH7SR

--- In loopantennas@..., "N.Kantor" <nkantor@m...> wrote:

Hello All,

I' have built a shielded loop for SW (1M diameter) which works very
nice.

Now I want to build a preamplifier for that antenna.

I have found a scheme for an amplifier on the Net by Lyle Koehler -

As I live on a boat and there no electronic shop within 500 km from
where I live, I wonder if any of you know if it is possible to

order a

kit
for that amplifier on the Net ( or any other preamplifier which is
similar to Lyle's ).

Any advice ?

73

Niki

You might want to check out the loopantennas yahoo
group.


--- "N.Kantor" <nkantor@...> wrote:

Hello All,

I' have built a shielded loop for SW (1M diameter)
which works very
nice.

Now I want to build a preamplifier for that antenna.

I have found a scheme for an amplifier on the Net by
Lyle Koehler -


As I live on a boat and there no electronic shop
within 500 km from
where I live, I wonder if any of you know if it is
possible to order a
kit
for that amplifier on the Net ( or any other
preamplifier which is
similar to Lyle's ).

Any advice ?

73

Niki

_______________________________
Do you Yahoo!?
Declare Yourself - Register online to vote today!

I already have a photo of the capacitor uploaded in
the photo section as stated in the original post. Here
is a web page that details how to build your on
capacitors.

It takes some time for all the pictures to load. The
drawings for the stator, rotor, and endplates are all
in metric. I made my capacitor slightly larger to
allow using 1/4-inch hardware. 6 mm is close but
slightly smaller and the 1/4-20 nuts would have
extended out past the stator vanes slightly and I did
not want it looking like that. Here is a direct link
to the photo of my homebrew capacitor; I hope it works
anyway hi!

My test loop was made from RG-8 coax used as the
element and an old split stator capacitor. It was
everything you did not want to do in building one!
Small diameter and high loss in the element as it's
not a solid conductor and the capacitor was not welded
across the top of the rotor. I still made contacts on
it! The new Magloop is going to be built without the
built-in losses of the test or fold up portable loop
but will still transport nicely in the pickup bed of
my truck.

--- furman2020 <k5qa@...> wrote:

Please post pictures and diagrams of your new loop
and butterfly cap. I am very interested in building
the same thing, except mabe for 80 & 160. Also,
please give us details on the performance of your
new loop system, compared to dipole or vertical if
possible. Thanks.
Furman2020 K5QA

--- In loopantennas@..., "n4zou"
<n4zou@y...> wrote:

I just finished a project I have been working on

the last few
weeks.

A large Butterfly capacitor for my soon to be

built 20 and 40
meter

transmitting type Magloop. It is 10-pF minimum and

100 pF maximum

with spacing for 12,000 volts. It is made from 15

gauge copper
sheet

metal, 1/4-20 all thread, 1/4-20 nuts, and

Plexiglas. I used
aviation

snips to cut the copper, a drill press for the

holes and a skill
saw

for the Plexiglas. Testing on another 20 and

40-meter loop
requires

17-pF at 14.350 and 91-pF at 7.0 MHz. The loop

will also work on
30

meters as well. I just uploaded photos of the

capacitor in the
photo

section. Just click on the N4ZOU folder. The old

test loop used RG-
8

coax as the element and a split stator capacitor.

You had to add a

second capacitor to get it to work on 40 meters.

This new setup
will

use 3/4 inch copper pipe for the element and will

have continuous

coverage between 14.350 and 7 MHz.

__________________________________________________
Do You Yahoo!?
Tired of spam? Yahoo! Mail has the best spam protection around

Hello All,

I' have built a shielded loop for SW (1M diameter) which works very nice.

Now I want to build a preamplifier for that antenna.

I have found a scheme for an amplifier on the Net by Lyle Koehler -

As I live on a boat and there no electronic shop within 500 km from where I live, I wonder if any of you know if it is possible to order a kit
for that amplifier on the Net ( or any other preamplifier which is similar to Lyle's ).

Any advice ?

73

Niki

Please post pictures and diagrams of your new loop
and butterfly cap. I am very interested in building
the same thing, except mabe for 80 & 160. Also,
please give us details on the performance of your
new loop system, compared to dipole or vertical if
possible. Thanks.
Furman2020 K5QA

--- In loopantennas@..., "n4zou" <n4zou@y...> wrote:

I just finished a project I have been working on the last few

weeks.

A large Butterfly capacitor for my soon to be built 20 and 40

meter

transmitting type Magloop. It is 10-pF minimum and 100 pF maximum
with spacing for 12,000 volts. It is made from 15 gauge copper

sheet

metal, 1/4-20 all thread, 1/4-20 nuts, and Plexiglas. I used

aviation

snips to cut the copper, a drill press for the holes and a skill

saw

for the Plexiglas. Testing on another 20 and 40-meter loop

requires

17-pF at 14.350 and 91-pF at 7.0 MHz. The loop will also work on

30

meters as well. I just uploaded photos of the capacitor in the

photo

section. Just click on the N4ZOU folder. The old test loop used RG-

8

coax as the element and a split stator capacitor. You had to add a
second capacitor to get it to work on 40 meters. This new setup

will

use 3/4 inch copper pipe for the element and will have continuous
coverage between 14.350 and 7 MHz.

I just finished a project I have been working on the last few weeks.
A large Butterfly capacitor for my soon to be built 20 and 40 meter
transmitting type Magloop. It is 10-pF minimum and 100 pF maximum
with spacing for 12,000 volts. It is made from 15 gauge copper sheet
metal, 1/4-20 all thread, 1/4-20 nuts, and Plexiglas. I used aviation
snips to cut the copper, a drill press for the holes and a skill saw
for the Plexiglas. Testing on another 20 and 40-meter loop requires
17-pF at 14.350 and 91-pF at 7.0 MHz. The loop will also work on 30
meters as well. I just uploaded photos of the capacitor in the photo
section. Just click on the N4ZOU folder. The old test loop used RG-8
coax as the element and a split stator capacitor. You had to add a
second capacitor to get it to work on 40 meters. This new setup will
use 3/4 inch copper pipe for the element and will have continuous
coverage between 14.350 and 7 MHz.

I actually had two slinkies in my apartment bedroom along two adjacent walls
(~12 ft long for each slinky). The only time I ever made a contact with them
was with them on 40m and the other station was another QRP operator in
Northeast Oklahoma (I'm in Central Oklahoma/OKC). I blamed the poor performance
on other metalic objects in the near field (ducting, wiring). It might have
also been due to being inside.

I wish I could get my slinkies copper plated - then I think they might be
pretty efficient.

- Daniel / AA0NI

--- Jerome <jeromeg@...> wrote:

Jeff,

Not too sure about the 51J3 but some of the old Collins commercial
receivers had two antenna inputs. One was 50 Ohm with a coaxial
fitting and the other was a nominal 500 Ohm with screw terminals. If
you have the 500 Ohm input you might find using it works better.

73,

'Bear' NH7SR

--- In loopantennas@..., "Jersey Jeff" <jwewers@h...>
wrote:

A couple general antenna questions - is bare wire to be preferred

to

plastic coated wire? Thicker wire better than thinner? I own a
Collins 51J-3. I'm using about 20 feet of ordinary speaker wire
(double wire, plastic coated, with the ends twisted together) as an
indoor antenna. I have the wire looped around the top of the wall
unit in which the radio sits. Reception is pretty good - probably

a

credit more to the Collins than to my antenna! Can I do better
within the confines of a 8'X10' room? Bear in mind I need wife's
approval too!