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!

It makes no difference to the performance of the
antenna if the wire used is coated or bare. However,
if you're using it inside then you really want that
nice plastic covering! Also same with the wire size,
you need really thick wire of 1/2 inch or more to see
any difference and all this does is shorten the
antenna length if you use it for transmitting. For
receiving, more wire length is always better! Split
that speaker wire and either double it's length or use
the second wire as a ground counterpoise, which would
give you a dipole type antenna. Try the dipole setup
first and if you don't see improvement add the wire to
double your now random wire antenna.
--- Jersey Jeff <jwewers@...> 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!

__________________________________
Do you Yahoo!?
Read only the mail you want - Yahoo! Mail SpamGuard.

Hi Jeff: You may use your wife for a form to hold the 1,000 feet of number
12 awg solid wire, and place it next to the window closest to your Collins.
You'll get great reception with no hassles from YL. Do the dutiful thing of
submitting a missing persons report, but keep a straight face when
interviewed. Good luck.
Actually, you will probably enjoy better results with the speaker wire
split, and therefore not doubled back on itself. Placing the wire behind the
window coverings will help in the domestic relations department, and if
possible, place it just on the perimeter of the glass. Again, good luck.
theboyd

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!

I read at this link...



... that the voltage rating for RG-8 and RG-213 is 4000V and 3700V. I
don't know if anyone else can verify these facts.

If this is the case... then one might be able to load this antenna to
50-60 watts safely (using the magnetic loop calculator in the groups
files section).

I based this on the following information inputted into the magloop
calculator:

20 ft circumference
0.5 in diameter tubing
7 MHz operating frequency

25 Watts ... 2.0 kV (probably the highest 'safe' power to use)
50 Watts ... 2.8 kV
60 Watts ... 3.1 kV
87 Watts ... 3.7 kV
100 Watts ... 4.0 kV (that would be too close to the edge for my comfort)

Interestingly enough - a loop of this size is calculated at 43%
efficiency when using this magloop calculator. I guess I was using a
different program (DOS based) to derive the efficiency values I
previously posted (10-15% efficiency from memory). When I rerun it
using the DOS program, it takes into account height above ground, and
it suggests more like 24% efficiency when placed .71 meters above
ground at the lowest point... and at 50m, it is 44.5% (very comparable
to the magloop calculator). However, I also notice a discrepency
between the two calculators when it comes to calculating capacitor
voltages ... it suggests that if I use 20W of power with a similar
antenna, that the voltage will be about 3.7kV.

I will be posting the alternate DOS based calculator that I found
somewhere on the web a few months ago.

- Daniel

---

Do you Yahoo!?
Get it on your mobile phone.

Ditto! In 6 weeks you will have enough oxidation built up around
those joints that the transmit efficiency will drop like a stone.
Connection resistance on transmitting loops needs to be held to an
absolute minimum. There's a lot of current flowing at the feedpoints
and very high voltages _with_ high currents at the capacitor. Best if
you can solder these joints and then insulate them from the weather.

73,

'Bear' NH7SR

--- In loopantennas@..., "Michael Stevenson"
<portstevos@t...> wrote:

Congradulations, it looks great! I like your method of non -

soldering the cables, unfortunately, it would not last long around
here where I live by the seaside, I sprayed clear protective lacquer
onto my polished copper loop but it is still managing to corrode in
spots, I presume you are living far inland away from any salt spray?

Great photos anyway and I enjoyed looking!
Best regards!

Michael Stevenson,
Australia.
----- Original Message -----
From: loopantennas@...
To: loopantennas@...
Sent: Thursday, October 14, 2004 5:16 AM
Subject: [loopantennas] New file uploaded to loopantennas




Hello,

This email message is a notification to let you know that
a file has been uploaded to the Files area of the loopantennas
group.

File : /40m compact loop photos/40m loop.zip
Uploaded by : aa0ni <aa0ni@y...>
Description : Zip file containing half size photos of the AA0NI

40m compact transmitting loop

You can access this file at the URL:

20loop%20photos/40m%20loop.zip

To learn more about file sharing for your group, please visit:


Regards,

aa0ni <aa0ni@y...>








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Service.

Jerome,

I have been using degaussing coils as VLF (sub 30KHz) antennas for
reception of sferics. They work very well down low. With the ~0.047
uF input capacitance of my AD620 preamp the coil scavenged from a 27"
TV (about 1 meter across) resonates at about 6.3 KHz. I have tried it
with my Jackson Harbors LF up-converter with lackluster results
probably due to severe mismatching. Haven't tried it at MW or HF yet.

73,

'Bear' NH7SR

--- In loopantennas@..., "Jerome" <jeromeg@m...> wrote:

Has anyone done anything with a degaussing coil loop antenna?

Took a 27 inch Sony apart and the coil is something like 4 feet
across. Hooked it up to my Sony ICF2010. First thing I noticed was
very little background noise. Second there was QRM on 160 meters, 80
meters was very good. Performance started to drop off at 7 Mz, but
still useable. How are they constructed, do you treat them like a
coax loop? Any thoughts would be appreciated, Jerry

_______________________________________________
No banners. No pop-ups. No kidding.
Make My Way your home on the Web -

开云体育

One problem with using RG-8 or RG-213 coax as a
capacitor and lowers the voltage rating is the shield.
When it's cut you have many sharp copper wire ends
that greatly increases the probability that you get an
arc over at either ends of the peace of coax used as a
capacitor. You will also have problems with the change
of resonance as that peace of coax changes positions
in relation to the loop element. The fix is to simply
remove the shield and replace it with a suitable
length of 3/8 copper tubing. This copper tubing should
be clamped rigidly to the element and at least 1 inch,
preferably 2 inches of the center wire and insulation
sticking out of each end of the copper tubing. Also
make sure there are no sharp points or burs on each
end of the copper tubing. The copper tubing is clamped
on one side of the element gap and the center wire and
insulation soldered to the other side of the element
gap. This will increase the voltage rating and make
for a steady resonance/frequency point.
--- aa0ni@... wrote:

I read at this link...



... that the voltage rating for RG-8 and RG-213 is
4000V and 3700V. I
don't know if anyone else can verify these facts.

If this is the case... then one might be able to
load this antenna to
50-60 watts safely (using the magnetic loop
calculator in the groups
files section).

I based this on the following information inputted
into the magloop
calculator:

20 ft circumference
0.5 in diameter tubing
7 MHz operating frequency

25 Watts ... 2.0 kV (probably the highest 'safe'
power to use)
50 Watts ... 2.8 kV
60 Watts ... 3.1 kV
87 Watts ... 3.7 kV
100 Watts ... 4.0 kV (that would be too close to the
edge for my comfort)

Interestingly enough - a loop of this size is
calculated at 43%
efficiency when using this magloop calculator. I
guess I was using a
different program (DOS based) to derive the
efficiency values I
previously posted (10-15% efficiency from memory).
When I rerun it
using the DOS program, it takes into account height
above ground, and
it suggests more like 24% efficiency when placed .71
meters above
ground at the lowest point... and at 50m, it is
44.5% (very comparable
to the magloop calculator). However, I also notice a
discrepency
between the two calculators when it comes to
calculating capacitor
voltages ... it suggests that if I use 20W of power
with a similar
antenna, that the voltage will be about 3.7kV.

I will be posting the alternate DOS based calculator
that I found
somewhere on the web a few months ago.

- Daniel

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

Here is a link to a PDF file producer with no
advertisements and is freeware. There is a beg screen
for support and donations but it does not impact the
program features at all. You get professional looking
PDF files that are super easy to create. Use a printer
driver that will produce Postscript file dumps instead
of printing to a real printer. It will even "print"
graphics in programs that normally will not let you do
that by using the Alt-Screen print function and then
paste into a Postscript edit program.



--- Steve Greenfield <alienrelics@...> wrote:

Thanks!

FYI, if anyone wants to post as a PDF as Dan is
doing, there is a
free/shareware tool to create PDFs from any program.
It works by
selecting it as if it were a printer, and then just
printing.
Instead it saves it as a PDF file.

It's $9.95 shareware, or free with an ad each time
you run it (end
viewers don't get ads, just when you create a PDF).



Or if you use Open Office, you can create PDFs.

Posting as PDF is far superior to posting as MS DOC
format, as MS
does their best (worst?) to make it so 1. no one
else can open the
format (the next MS Office formats are suppose to
contain
encryption illegal to even try to decrypt legally
with a different
program, under the DMCA) 2. sometimes incompatible
with different
versions so you'll have to upgrade to the latest
version of MS
Office.

Steve Greenfield

--- Daniel Reynolds <aa0ni@...> wrote:

When I get a chance to, I'll create a Word

document and print it

to a PDF file
for everyone's perusal. I'll include a list of

parts (and what I

paid for them)
and the detailed photos (enlarged).

- Daniel/AA0NI

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

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

Hello,

This email message is a notification to let you know that
a file has been uploaded to the Files area of the loopantennas
group.

File : /magloop4.exe
Uploaded by : aa0ni <aa0ni@...>
Description : DOS based program to calculate loop specifications - uses metric values only

You can access this file at the URL:


To learn more about file sharing for your group, please visit:


Regards,

aa0ni <aa0ni@...>

I read at this link...



... that the voltage rating for RG-8 and RG-213 is 4000V and 3700V. I
don't know if anyone else can verify these facts.

If this is the case... then one might be able to load this antenna to
50-60 watts safely (using the magnetic loop calculator in the groups
files section).

I based this on the following information inputted into the magloop
calculator:

20 ft circumference
0.5 in diameter tubing
7 MHz operating frequency

25 Watts ... 2.0 kV (probably the highest 'safe' power to use)
50 Watts ... 2.8 kV
60 Watts ... 3.1 kV
87 Watts ... 3.7 kV
100 Watts ... 4.0 kV (that would be too close to the edge for my comfort)

Interestingly enough - a loop of this size is calculated at 43%
efficiency when using this magloop calculator. I guess I was using a
different program (DOS based) to derive the efficiency values I
previously posted (10-15% efficiency from memory). When I rerun it
using the DOS program, it takes into account height above ground, and
it suggests more like 24% efficiency when placed .71 meters above
ground at the lowest point... and at 50m, it is 44.5% (very comparable
to the magloop calculator). However, I also notice a discrepency
between the two calculators when it comes to calculating capacitor
voltages ... it suggests that if I use 20W of power with a similar
antenna, that the voltage will be about 3.7kV.

I will be posting the alternate DOS based calculator that I found
somewhere on the web a few months ago.

- Daniel

Hello,

This email message is a notification to let you know that
a file has been uploaded to the Files area of the loopantennas
group.

File : /40m compact loop photos/40m loop.zip
Uploaded by : aa0ni <aa0ni@...>
Description : Zip file containing half size photos of the AA0NI 40m compact transmitting loop

You can access this file at the URL:


To learn more about file sharing for your group, please visit:


Regards,

aa0ni <aa0ni@...>

Thanks!

FYI, if anyone wants to post as a PDF as Dan is doing, there is a
free/shareware tool to create PDFs from any program. It works by
selecting it as if it were a printer, and then just printing.
Instead it saves it as a PDF file.

It's $9.95 shareware, or free with an ad each time you run it (end
viewers don't get ads, just when you create a PDF).



Or if you use Open Office, you can create PDFs.

Posting as PDF is far superior to posting as MS DOC format, as MS
does their best (worst?) to make it so 1. no one else can open the
format (the next MS Office formats are suppose to contain
encryption illegal to even try to decrypt legally with a different
program, under the DMCA) 2. sometimes incompatible with different
versions so you'll have to upgrade to the latest version of MS
Office.

Steve Greenfield

--- Daniel Reynolds <aa0ni@...> wrote:

When I get a chance to, I'll create a Word document and print it
to a PDF file
for everyone's perusal. I'll include a list of parts (and what I
paid for them)
and the detailed photos (enlarged).

- Daniel/AA0NI

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

When I get a chance to, I'll create a Word document and print it to a PDF file
for everyone's perusal. I'll include a list of parts (and what I paid for them)
and the detailed photos (enlarged).

- Daniel/AA0NI

--- Steve Greenfield <alienrelics@...> wrote: