--- Michael Hebert <qrpbear@...> wrote:

With the kind of bandwidth you are getting on 40m I would say the
loop's Q is seriously degraded. You should only have about 15-20 KHz
between 1.5:1 points. KI6GD's loop calculator predicts an efficiency
of about 28% for a loop made of 1/4" copper pipe. I would say that
your loop's efficiency is well below that figure especially since the
BuddiPole beat it out. The BuddiPole is probably only about 10%
efficient on 40m.

I agree... The loop is supposed to be a tuned circuit. With the unusually broad
bandwidth, I think it has losses somewhere.

Try a CW keydown test for a couple of minutes then feel the tubing in
the area around the gap. If it feels warm you have some nasty
dielectric losses occuring. What kind of insulation does the wire use
and what is it's voltage rating? If it's the common 600 Volt wire the
insulation is probably PVC which is OK so long as you use the white
wire rather than the black or green wire. PTFE insulated wire would
be preferable from a loss standpoint. The ends of the wire should be
smoothed off and well insulated. Any sharp points there could arc or
develop corona discharges.

I will try that key down test some time. The wire is #10 stranded THHN with a
white insulating jacket rated for 600V. I wonder if I would have done better to
use solid instead of stranded. I tried to use electric tape over the ends of
the wire to reduce short circuit/corona on the ends of the capacitor-wire.

I still think your "wire inside" tuning idea is a good one but you
definitely should be getting better results. It may be necessary to
bridge the gap with a fixed capacitor and use the wire for fine
tuning.

I may try using a piece of coax for a capacitor and see how that performs. I do
not have access to high voltage capacitors (fixed or variable).

Since I'm limited on power (Elecraft K2 @ 15W), the loop would be better used
on 20m where it should be more efficient for its size. I was lucky to be heard
last night using 15W SSB into the buddipole at its height. I'm normally a CW
op, but my mini-paddles lost one of the leads (for the 2nd time).

FWIW - the buddipole received everything about 10dB stronger than the loop. The
long wire wasn't any stronger than the loop (although I can't tell if it was
weaker than the loop). There are overhead utility lines that pass over the last
30 feet of the wire. Most operators were complaining about all of the
noise/static crashes they were hearing last night, and I was hearing most
everyone clearly. I don't know whether to attribute this to the loop antenna,
antenna height, propagation, K2 receiver, or a combination of these.

73,
Daniel / AA0NI

开云体育

Daniel,

With the kind of bandwidth you are getting on 40m I would say the
loop's Q is seriously degraded. You should only have about 15-20 KHz
between 1.5:1 points. KI6GD's loop calculator predicts an efficiency
of about 28% for a loop made of 1/4" copper pipe. I would say that
your loop's efficiency is well below that figure especially since the
BuddiPole beat it out. The BuddiPole is probably only about 10%
efficient on 40m.

Try a CW keydown test for a couple of minutes then feel the tubing in
the area around the gap. If it feels warm you have some nasty
dielectric losses occuring. What kind of insulation does the wire use
and what is it's voltage rating? If it's the common 600 Volt wire the
insulation is probably PVC which is OK so long as you use the white
wire rather than the black or green wire. PTFE insulated wire would
be preferable from a loss standpoint. The ends of the wire should be
smoothed off and well insulated. Any sharp points there could arc or
develop corona discharges.

I still think your "wire inside" tuning idea is a good one but you
definitely should be getting better results. It may be necessary to
bridge the gap with a fixed capacitor and use the wire for fine
tuning.

73,

'Bear' NH7SR

--- In loopantennas@..., aa0ni@y... wrote:

I was able to get the antenna to tune up on 40m, but had to switch
from magnetic coupling to a direct matching system (shield of coax

at

center point of loop tubing, and moving end of coax along the

length

of the loop tubing until properly matched). Before I did this, the
best I could get on 40m was 2:1. Now I get 1:1.

I get a pretty broadband response on 40m (160kHz 2:1, 110kHz

1.5:1).

I'm concerned that maybe I'm doing something wrong. I don't have

the

sharp response expected from a Hi-Q circuit on 40m. Is it possible,
like was mentioned, that the distributed capacitance is making the
antenna broader in frequency response? Since it is broader in
frequency response - does that hint of great inefficiency? I don't
have a field strength meter to run a comparison.

Unfortunately, it does not seem to be very efficient on 40m. I was
running 10-15W SSB on 40m, and my buddipole (at 9-10 ft) did better
than both the 20' loop and my 100' wire (both at 5'). This was with

a

station near Dallas (I'm in OKC) near local sunset. He was running
500W to an inverted V up 1/4 wave (35 feet). The buddipole was just
above the noise level. Both the loop and longwire were unreadable.

Hoping there's something I can do to remedy this loop (other than
putting it back on 20m).

- Daniel

Chris,

Sounds like you made a very fine loop, indeed! The only thing I would
have done differently is to make the coupling loop about 1.5" to 2"
in from the main loop winding. That helps improve the Q (Quality
factor) and sharpens up the tuning. It wouldn't make much difference
as far as signal strength is concerned.

As far as connections go... Yes wire one end of the loop winding to
the solder tabs on the variable capacitor and the other end to the
frame. It doesn't matter which end goes where. One end of the
coupling loop goes to antenna input and the other to ground on your
receiver. Twisting the wires between the loop and receiver at about 2
twists to the inch will make that portion act as a transmission line
rather than a short antenna. This will improve the loop's ability to
null interference when you rotate it.

You don't need a diode between the loop and the receiver... just hook
it up, tune it up and enjoy!!

73,

'Bear' NH7SR

I was able to get the antenna to tune up on 40m, but had to switch
from magnetic coupling to a direct matching system (shield of coax at
center point of loop tubing, and moving end of coax along the length
of the loop tubing until properly matched). Before I did this, the
best I could get on 40m was 2:1. Now I get 1:1.

I get a pretty broadband response on 40m (160kHz 2:1, 110kHz 1.5:1).
I'm concerned that maybe I'm doing something wrong. I don't have the
sharp response expected from a Hi-Q circuit on 40m. Is it possible,
like was mentioned, that the distributed capacitance is making the
antenna broader in frequency response? Since it is broader in
frequency response - does that hint of great inefficiency? I don't
have a field strength meter to run a comparison.

Unfortunately, it does not seem to be very efficient on 40m. I was
running 10-15W SSB on 40m, and my buddipole (at 9-10 ft) did better
than both the 20' loop and my 100' wire (both at 5'). This was with a
station near Dallas (I'm in OKC) near local sunset. He was running
500W to an inverted V up 1/4 wave (35 feet). The buddipole was just
above the noise level. Both the loop and longwire were unreadable.

Hoping there's something I can do to remedy this loop (other than
putting it back on 20m).

- Daniel

Daniel,

Very interesting post! I like your idea for the tuning capacitor. I
thought about a somewhat similar approach using a larger diameter
copper pipe sliding back and forth over the gap in the loop but never
got around to building it. Your method would be considerably less
complicated.

I ran a quickie calculation using KI6GD's loop calculator which shows
an efficiency of 79.9% and a bandwidth of 75.3 KHz. Since you are
getting 300 KHz the capacitor is probably lowering the loop Q due to
linear loading. Efficiency would be somewhat less but probably not
any detectable difference in signal strength when you're transmitting.
KI6GD's calculator also predicts 3.2 kV across the capacitor assuming
a lumped capacitance at the gap. It will probably be considerably
less than this with distributed capacitance.

I also found that squashing the coupling loop improved matching to
the main loop. Positioning it dead center or offset to either side
did not make any significant difference on my 10' circumference loop.

At low mounting heights the MagLoop does exhibit better low angle
performance than a dipole at the same height. The pattern of a
MagLoop mounted 1 loop diameter above ground is primarily straight up
but it does have better low angle figures than a dipole when modeled
in EZNEC. Raising the loop higher improves the low angle figures even
more and the pattern begins to change as you go higher than 1/4
wavelength above ground. The high angle pattern begins to flatten out
and the low angle response starts moving towards even lower angles.
Above 1/2 wavelength mounting height lobes begin to develop in the
vertical radiation angle patterns.

Any performance comparison with a dipole has to be tempered by the
fact that a dipole exhibits about 2.38 dB gain over isotropic while a
MagLoop shows a loss compared to isotropic with the loss being
relative to the loop size. The characteristics of the ground
surrounding the antennas at a distance of up to 1/4 mile also needs
to be taken into consideration since it directly affects the take-off
angle of the antenna.

I have not found rotating my loop to offer any benefit. The azimuthal
pattern of a MagLoop at vertical angles above 30 degrees is
essentially omnidirectional. Mine is situated in a North/South plane
and seems to work just as well for all directions.

Thanks again for such an informative post and the great idea!

73,

'Bear' NH7SR

--- In loopantennas@..., aa0ni@y... wrote:

I just joined the list because I've been wanting to build a compact
transmitting loop for many months now, and I was met with good
success late last night (around 12-1 AM, while I was waiting for

the

caffeine to settle down in my system... but that's another story).

A couple goals I had were simplicity in design (fixed tuning, basic
monoband/QRP use, no expensive tuning capacitor), simple assembly

(no

pipe soldering), readily available materials (Lowe's), and high
efficiency (circumference >1/10 wavelength, very low resistances).

I

want the design to be reproduceable so that a ham who didn't have
access to an antenna analyzer could build one of these and know

that

it would work with minimal amount of fuss.

I used 20 ft of 1/4" flexible copper tubing (less than $10) taped

to

a 1/2" PVC pipe cross. The advantage of the flexible copper tubing

is

that there are no joints to solder, minimizing any resistive

losses.

The disadvantage of 1/4" tubing is that you need to use alot of it

to

make up for its small diameter.

For tuning, I used a 2 ft piece of #12 THHN solid wire. This wire

was

placed in both open ends of the pipe, and then moved back and forth
until proper tuning was achieved. This type of tuning is similar in
action to a butterfly capacitor (no resistive losses from a stator)
or a trombone capacitor, except that it is using the antenna tubing
itself as part of the plates, and the wire is coupling the two

sides

together just like the butterfly stator (very low resistance -
improving efficiency).

The #12 THHN was free, but I'm going to acquire some #10 THHN which
is the largest size I've found that will fit in the 1/4" tubing. By
using #10 THHN, there will be less problems with wire not being
equidistant from the inside of the tubing. The #12 can 'float'

around

the inside of the tubing. Using #10 should give consistent results.
It will also increase the capacitance as the gap between the
innerwall of the tubing and the #10 wire decreases.

The antenna is fed with 20 ft of RG-8x (8-mini). A four foot loop

was

construced on the end with the center conductor soldered to the
shield/braid of the coax four feet back from the end of the coax.

I realize that 20' is not really 'compact' for 20m. For me, this

was

more a proof of concept. I intend on using the 20' for 30m or 40m.

I

will probably try to use 10' for 20m.

The results? 2:1 SWR bandwidth is about 300 kHz on 20m (but tuning
was tricky). The SWR was measured as it was leaning up against a
wooden fence in the backyard, and the bottom of the loop was less
than 2 feet off the ground. The coupling loop is very flat against
the copper tubing. Instead of being a nice circle, it is a very
squashed oval (which brought the SWR down from 2:1 when circular to
1.3:1 when a flat oval). Before I started mounting the copper

tubing

to the PVC frame, I should have straightened the copper tubing out
and marked off the half point and quarter points so I could be sure

I

was mounting the coupling loop at the center point. This would have
removed the guess work from mounting the antenna to the PVC support.

Because the tuning is so touchy, my next goal is to mark the wire
where it now sits in the tubing. I'm guessing that I am using way

too

much wire for the capacitor on 20m. I want to try to find a wire
length, that when centered between the two openings, will tune the
loop to near 14.000. Then, as the wire is slid to either side, the
capacitance decreases (I'm assuming), and the antenna's resonant
frequency will go up. If I shortened the 20m capacitor wire down to
it's smallest effective length for the low end of the band, any

small

adjustment should hopefully result in a small increase (only) in
resonant frequency. It might even make it possible to mark the wire
to precisely tune the antenna - e.g. moving the wire 1" from center
moves resonance up ### kHz.

I think that if a proven design can be established where a certain
known length of #10 wire combined with a certain length of 1/4"
tubing will allow a user to operate on a particular band - more
operators will be using loops in antenna restricted environments.

Thanks for the bandwidth, and any comments you have about this

design.

- Daniel / AA0NI
Oklahoma City

p.s. I'd be curious to know how close to the ground you use your
loop, and does it act more like an NVIS antenna like a dipole

would,

or do you get out better towards the horizon then the dipole at the
same height. There seems to be quite a debate about the loops

ability

to outperform a dipole antenna at a low height.

I just dug up one of those little square loops outa my junkbox and
took a look at it. It has 6 turns around the circumference (about 4"
by 5") with the remaining 3' of wire twisted together at about 1
twist per inch to act as a transmission line (probably about 70 ohms
or so).

As Bruce says, it's not an efficient design by any means. I seriously
doubt that it's tuned. A single 25' strand of wire running around the
baseboards should outperform it by a wide margin... or better yet, a
_real_ tuned loop. I have a 14" square Pizza Box tuned loop that I
use for AM. The difference between the stock plastic "excuse-for-a-
loop" and my dinky Pizza Box loop is like night and day! The Pizza
Box sucks up signals that aren't even there on the plastic toy.

BTW, Bruce Carter's calculator works very well also.

73,

'Bear' NH7SR

--- In loopantennas@..., "Bruce Carter" <brucec@m...>
wrote:

This is Bruce (not Brian) Carter. My opinion on those little loops
that come with receivers is that they are probably NOT tuned loops
with the varactors or tuning capacitor inside the units. I think
that they are de-tuned badly to allow broadband reception, and then
they make up the difference by using a lot of gain on the front
end. If they are tuned, any loop with the same inductance should
track with their internal capacitance. Since they are rectangular,
you would have to use my new formula (which is not on the loop
antenna page yet, but is on my work page at:


kb=analog&obj=498

You will have to cut and paste that URL. You can also get there by
going to www.ti.com/amplifier_utilities and clicking the design
calculator link at the bottom. The loop antenna stuff is really
intended for a line of chips for wireless keyboards and mice, but

it

works very well for AM antennas as well. Once you get the correct
inductance from the dimensions and number of turns of your antenna,
design a bigger one for the same inductance and you should be fine.


--- In loopantennas@..., "Michael Hebert"

<qrpbear@y...>

wrote:

Chris,

Check out Brian Carter's web page at...

<>

for a very simple and effective AM loop antenna.

What most people don't realize about those AM loop antennas that

come

with stereo receivers is that are not always meant to be used as

they

are. Quite often you get better results if you unwind them and

string

the wire around the room (or even along the baseboard).

73,

'Bear' NH7SR

--- In loopantennas@..., "lockmanslammin"
<lockmanslammin@a...> wrote:

I have a yamaha reciever, that has an am antenna hookup with

an "in"

and a ground. It came with a small plastic loop antenna, that

doesn't

quite seem to get the station I want. So i searched am antennas
online to find LOTS of info, and some plans, but they all seem

to

be

to big or overly complex for my needs. what I'm looking for is

plans

for an antenna for a modern reciever with the antenna hookups I
desribed. and not too huge, maybe like 2 feet or so in

diameter.

It

seems to me that most of the stuff I have read deals more with

the

construction of the frame and stuff, and less about the wiring

etc.

I

will have no problem figuring out a sutible frame design and

what I

was really looking for was a simple description of the correct
windings for a said diameter. Also I'm not sure how to hook it

up

to

the reciever, do I need this "coupling winding"? Or in my case

do I

just hook up the main windings to the antenna hookup on the

reciever.

Also, there is no variable resistor on the little plastic loop

that

came with the reciever, does this mean that I don't need one if

I

build my own?

I thank you for any comments/ suggestions that would help me

out. I

don't think I will be getting into this as a hobby or anything,

I

was

just hoping to make one that would get the station I want,

which

is

570 AM, which has somwe interesting stuff on it at night, but

it

would be cool if the loop worked through the whole band

decently

also

as I thought it might be fun to surf the whole spectrum for

some

cool

talk shows.

Thanx again in advance,
chris

开云体育

This is Bruce (not Brian) Carter. My opinion on those little loops
that come with receivers is that they are probably NOT tuned loops
with the varactors or tuning capacitor inside the units. I think
that they are de-tuned badly to allow broadband reception, and then
they make up the difference by using a lot of gain on the front
end. If they are tuned, any loop with the same inductance should
track with their internal capacitance. Since they are rectangular,
you would have to use my new formula (which is not on the loop
antenna page yet, but is on my work page at:


kb=analog&obj=498

You will have to cut and paste that URL. You can also get there by
going to www.ti.com/amplifier_utilities and clicking the design
calculator link at the bottom. The loop antenna stuff is really
intended for a line of chips for wireless keyboards and mice, but it
works very well for AM antennas as well. Once you get the correct
inductance from the dimensions and number of turns of your antenna,
design a bigger one for the same inductance and you should be fine.


--- In loopantennas@..., "Michael Hebert" <qrpbear@y...>
wrote:

Chris,

Check out Brian Carter's web page at...

<>

for a very simple and effective AM loop antenna.

What most people don't realize about those AM loop antennas that

come

with stereo receivers is that are not always meant to be used as

they

are. Quite often you get better results if you unwind them and

string

the wire around the room (or even along the baseboard).

73,

'Bear' NH7SR

--- In loopantennas@..., "lockmanslammin"
<lockmanslammin@a...> wrote:

I have a yamaha reciever, that has an am antenna hookup with

an "in"

and a ground. It came with a small plastic loop antenna, that

doesn't

quite seem to get the station I want. So i searched am antennas
online to find LOTS of info, and some plans, but they all seem

to

be

to big or overly complex for my needs. what I'm looking for is

plans

for an antenna for a modern reciever with the antenna hookups I
desribed. and not too huge, maybe like 2 feet or so in diameter.

It

seems to me that most of the stuff I have read deals more with

the

construction of the frame and stuff, and less about the wiring

etc.

I

will have no problem figuring out a sutible frame design and

what I

was really looking for was a simple description of the correct
windings for a said diameter. Also I'm not sure how to hook it

up

to

the reciever, do I need this "coupling winding"? Or in my case

do I

just hook up the main windings to the antenna hookup on the

reciever.

Also, there is no variable resistor on the little plastic loop

that

came with the reciever, does this mean that I don't need one if

I

build my own?

I thank you for any comments/ suggestions that would help me

out. I

don't think I will be getting into this as a hobby or anything,

I

was

just hoping to make one that would get the station I want, which

is

570 AM, which has somwe interesting stuff on it at night, but it
would be cool if the loop worked through the whole band decently

also

as I thought it might be fun to surf the whole spectrum for some

cool

talk shows.

Thanx again in advance,
chris

I just joined the list because I've been wanting to build a compact
transmitting loop for many months now, and I was met with good
success late last night (around 12-1 AM, while I was waiting for the
caffeine to settle down in my system... but that's another story).

A couple goals I had were simplicity in design (fixed tuning, basic
monoband/QRP use, no expensive tuning capacitor), simple assembly (no
pipe soldering), readily available materials (Lowe's), and high
efficiency (circumference >1/10 wavelength, very low resistances). I
want the design to be reproduceable so that a ham who didn't have
access to an antenna analyzer could build one of these and know that
it would work with minimal amount of fuss.

I used 20 ft of 1/4" flexible copper tubing (less than $10) taped to
a 1/2" PVC pipe cross. The advantage of the flexible copper tubing is
that there are no joints to solder, minimizing any resistive losses.
The disadvantage of 1/4" tubing is that you need to use alot of it to
make up for its small diameter.

For tuning, I used a 2 ft piece of #12 THHN solid wire. This wire was
placed in both open ends of the pipe, and then moved back and forth
until proper tuning was achieved. This type of tuning is similar in
action to a butterfly capacitor (no resistive losses from a stator)
or a trombone capacitor, except that it is using the antenna tubing
itself as part of the plates, and the wire is coupling the two sides
together just like the butterfly stator (very low resistance -
improving efficiency).

The #12 THHN was free, but I'm going to acquire some #10 THHN which
is the largest size I've found that will fit in the 1/4" tubing. By
using #10 THHN, there will be less problems with wire not being
equidistant from the inside of the tubing. The #12 can 'float' around
the inside of the tubing. Using #10 should give consistent results.
It will also increase the capacitance as the gap between the
innerwall of the tubing and the #10 wire decreases.

The antenna is fed with 20 ft of RG-8x (8-mini). A four foot loop was
construced on the end with the center conductor soldered to the
shield/braid of the coax four feet back from the end of the coax.

I realize that 20' is not really 'compact' for 20m. For me, this was
more a proof of concept. I intend on using the 20' for 30m or 40m. I
will probably try to use 10' for 20m.

The results? 2:1 SWR bandwidth is about 300 kHz on 20m (but tuning
was tricky). The SWR was measured as it was leaning up against a
wooden fence in the backyard, and the bottom of the loop was less
than 2 feet off the ground. The coupling loop is very flat against
the copper tubing. Instead of being a nice circle, it is a very
squashed oval (which brought the SWR down from 2:1 when circular to
1.3:1 when a flat oval). Before I started mounting the copper tubing
to the PVC frame, I should have straightened the copper tubing out
and marked off the half point and quarter points so I could be sure I
was mounting the coupling loop at the center point. This would have
removed the guess work from mounting the antenna to the PVC support.

Because the tuning is so touchy, my next goal is to mark the wire
where it now sits in the tubing. I'm guessing that I am using way too
much wire for the capacitor on 20m. I want to try to find a wire
length, that when centered between the two openings, will tune the
loop to near 14.000. Then, as the wire is slid to either side, the
capacitance decreases (I'm assuming), and the antenna's resonant
frequency will go up. If I shortened the 20m capacitor wire down to
it's smallest effective length for the low end of the band, any small
adjustment should hopefully result in a small increase (only) in
resonant frequency. It might even make it possible to mark the wire
to precisely tune the antenna - e.g. moving the wire 1" from center
moves resonance up ### kHz.

I think that if a proven design can be established where a certain
known length of #10 wire combined with a certain length of 1/4"
tubing will allow a user to operate on a particular band - more
operators will be using loops in antenna restricted environments.

Thanks for the bandwidth, and any comments you have about this design.

- Daniel / AA0NI
Oklahoma City

p.s. I'd be curious to know how close to the ground you use your
loop, and does it act more like an NVIS antenna like a dipole would,
or do you get out better towards the horizon then the dipole at the
same height. There seems to be quite a debate about the loops ability
to outperform a dipole antenna at a low height.

Chris,

Check out Brian Carter's web page at...

<>

for a very simple and effective AM loop antenna.

What most people don't realize about those AM loop antennas that come
with stereo receivers is that are not always meant to be used as they
are. Quite often you get better results if you unwind them and string
the wire around the room (or even along the baseboard).

73,

'Bear' NH7SR

--- In loopantennas@..., "lockmanslammin"
<lockmanslammin@a...> wrote:

I have a yamaha reciever, that has an am antenna hookup with

an "in"

and a ground. It came with a small plastic loop antenna, that

doesn't

quite seem to get the station I want. So i searched am antennas
online to find LOTS of info, and some plans, but they all seem to

be

to big or overly complex for my needs. what I'm looking for is

plans

for an antenna for a modern reciever with the antenna hookups I
desribed. and not too huge, maybe like 2 feet or so in diameter. It
seems to me that most of the stuff I have read deals more with the
construction of the frame and stuff, and less about the wiring etc.

I

will have no problem figuring out a sutible frame design and what I
was really looking for was a simple description of the correct
windings for a said diameter. Also I'm not sure how to hook it up

to

the reciever, do I need this "coupling winding"? Or in my case do I
just hook up the main windings to the antenna hookup on the

reciever.

Also, there is no variable resistor on the little plastic loop that
came with the reciever, does this mean that I don't need one if I
build my own?

I thank you for any comments/ suggestions that would help me out. I
don't think I will be getting into this as a hobby or anything, I

was

just hoping to make one that would get the station I want, which is
570 AM, which has somwe interesting stuff on it at night, but it
would be cool if the loop worked through the whole band decently

also

as I thought it might be fun to surf the whole spectrum for some

cool

talk shows.

Thanx again in advance,
chris

Steve,

I have successfully used receiving type air variables for QRP
operation at 2 watts output. For 5 watts you should use something
with 1000 to 1200 Volt plate spacing. For 100 watts you will
definitely need a much higher voltage rating. There are sites on the
net describing homemade air variables, trombone capacitors using PTFE
tape as the dielectric and trombone capacitors using RG-8. Any of
these if carefully built and attached to the loop should work well.
They will also be considerably less expensive than a vacuum variable.
Make sure your connections are fat and solid. Don't use any kind of
compression fittings or screws to make connections. It's not just the
voltage that is high, the current is also very high at the point of
connection with the capacitor. Silver solder or weld the joints to
minimize resistance. If the joint gets warm after transmitting into
it for a few minutes you have too much resistance.

73,

'Bear' NH7SR

--- In loopantennas@..., "Steve" <Mercxx@a...> wrote:

Good afternoon,
My name is Steve, N4TKP located in Bartow, Florida and I am new

to

the list. I am interested in building and experimenting with small
transmitting loops. I have found alot of information so far and

the

links here helped me find a couple of tutorials on how to build a
basic one. I am planning on building the first one next weekend.

I

have a question though, where can I find the capacitors I need to
take my input power (5 watts for the first and then 100 watts

later)

and what should I try first, air variable or a vacumn variable?
Anyway have a great day and I would appreciate any suggestions or
hints that anyone could provide.

73
Steve N4TKP

Lui,

You didn't mention what floor your apartment is on but since you use
the word balcony I assume that you are not at ground level. You can
use the balcony railing as an antenna. If you have sliding doors with
aluminum frames you can use the frame as an antenna.

Any method that gets some some signal from outside the apartment will
work. You can connect directly to the antenna input on your Sangean
or just use an aligator clip to attach the wire to the antenna rod.

An L-network tuner _may_ help on some bands but since the ATS-909 is
designed for use with random length antennas it is probably not
necessary.

You would be surprised at what works for a receiving antenna. I live
in a ground floor apartment and currently have three antennas buried
3" underground, a small Ficus tree (no... not a wire in the tree...
the tree itself!) and an earth battery that I use for antennas. You
can't get much more stealthy than a buried or tree antenna. They all
work and work surprisingly well. I have a group here on Yahoo for
this type of antennas. You can check it out at...

<>

73,

'Bear' NH7SR

--- In loopantennas@..., "Lui" <Scanmaster_lui@h...>
wrote:

Hi There

Does anyone have any idears how to make at stealthy SW antenna.

My problem is that i live in an apartment, and we are not allowed

to

have any vissible antennas out side the building.

So my question is how to make an antenna that is very "invisible".

I have a smal balkon but my wife tells me not to use all the space
on it ... :-)

Another question :
Do i have to use an antenna tuner for my radio, (it?s an SAGEAN
ATS909), or is it okay just to plug the antenna directly to the
radio ?

If yes - do you know any where on the internet where i can find a
diagram on how to build it my self ??


Kind Regard from

Lui

These were posted on the earlier loop group so I thought i'd post
them on this one. The RF connector is a 75 ohm cable TV chassis
mount. It goes to hookup wire that is wound 10 turns around the
internal ferrite antenna in the radio. Makes a convenient way to
connect loop antennas to the unit. The 14" box loop antenna is BCB.
The poly capacitor is slavaged from a failed tranisitor radio. I
suspect that it is about 250 pf because if I have enough turns to
pick up 440 KHZ, it won't tune all the way up to 1600. That is what
the alligator clip is for. There is a tap midway on the coil that
allows tuning the other half of the band. The black windings are the
loop and the white is the coupling winding. I'll post another of the
big SW & MW "rook" wound loop as soon as I get a picture of it.

This page,new to me,caught my attention because in addition to good
info on loop & capacitor constuction, he has used a BBQ spit motor
for remote tuning.
Hmmm,two of them might allow even a novice to mount something light
(hula hoop) on the roof to rotate & remotely tune.
Probably would confirm your neighbor's suspicions,too.
www.qsl.net/mnqrp/Loop/Mag_Loops.htm

Good afternoon,
My name is Steve, N4TKP located in Bartow, Florida and I am new to
the list. I am interested in building and experimenting with small
transmitting loops. I have found alot of information so far and the
links here helped me find a couple of tutorials on how to build a
basic one. I am planning on building the first one next weekend. I
have a question though, where can I find the capacitors I need to
take my input power (5 watts for the first and then 100 watts later)
and what should I try first, air variable or a vacumn variable?
Anyway have a great day and I would appreciate any suggestions or
hints that anyone could provide.

73
Steve N4TKP

I have a yamaha reciever, that has an am antenna hookup with an "in"
and a ground. It came with a small plastic loop antenna, that doesn't
quite seem to get the station I want. So i searched am antennas
online to find LOTS of info, and some plans, but they all seem to be
to big or overly complex for my needs. what I'm looking for is plans
for an antenna for a modern reciever with the antenna hookups I
desribed. and not too huge, maybe like 2 feet or so in diameter. It
seems to me that most of the stuff I have read deals more with the
construction of the frame and stuff, and less about the wiring etc. I
will have no problem figuring out a sutible frame design and what I
was really looking for was a simple description of the correct
windings for a said diameter. Also I'm not sure how to hook it up to
the reciever, do I need this "coupling winding"? Or in my case do I
just hook up the main windings to the antenna hookup on the reciever.
Also, there is no variable resistor on the little plastic loop that
came with the reciever, does this mean that I don't need one if I
build my own?

I thank you for any comments/ suggestions that would help me out. I
don't think I will be getting into this as a hobby or anything, I was
just hoping to make one that would get the station I want, which is
570 AM, which has somwe interesting stuff on it at night, but it
would be cool if the loop worked through the whole band decently also
as I thought it might be fun to surf the whole spectrum for some cool
talk shows.

Thanx again in advance,
chris

Hi There

Does anyone have any idears how to make at stealthy SW antenna.

My problem is that i live in an apartment, and we are not allowed to
have any vissible antennas out side the building.

So my question is how to make an antenna that is very "invisible".

I have a smal balkon but my wife tells me not to use all the space
on it ... :-)

Another question :
Do i have to use an antenna tuner for my radio, (it?s an SAGEAN
ATS909), or is it okay just to plug the antenna directly to the
radio ?

If yes - do you know any where on the internet where i can find a
diagram on how to build it my self ??


Kind Regard from

Lui

Bruce, how about flat ribbon copper?
I know that it's available in rolls of one inch,
and four inch,widths (in 50 & 100 foot lengths)
since that's what you would use to ground
Polyphaser surge suppressors.
They (Polyphaser)vsuggest that it has "more
surface area than round wire, or braid.
"Lightening travels over the surface of a conductor...
as do radio waves. I wonder if this could be better
than multiple ROUND wire ribbon cable.
On the other hand, if a suitable diameter is
available, it probably wouldn't be insulated
in any way.

I don't know - I have never seen it at our local electronics
houses. Why don't you give it a try and see how it works? I would
be interested in the results. Of course it would give my calculator
a fit because the conductors have length and width and not a radius.

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