On 11 Dec 2010 23:28:18 GMT, Sébastien MEDARD wrote:

For now, I tried a lot of different things... The best result were on
loops.

Hi Sebastien,

This is a good lesson.

A big loop (1.6mx4 = 6.4 meters), one turn, with an air variable
capacitor + an inside loop connected to the coaxial cable seems to give
better ways to give something to eat to my receiver.

This is an excellent antenna for BCB and Tropical Bands.

Sometimes my air
capacitor was not powerful enough, in the lower bands if I remember
well... To improve that I will have to add a fixed capacitor (lets say
300pF) in parallel (to be bypassed) or more depending on the band I am
listening to.

This is a great solution.

For now I am just experimenting (with some simple wire),
but I think I will build a more solid one...

A big loop (1.6mx4 = 6.4 meters), one turn, with the the universal balun
from Wellbrook. Don't know why, but, it gives very good results, far
better than a long wire in my flat, or a short wire on my balcony... At
this time it seems there is a Ham Contest in Italia... I can get them
fully on 80m LSB/CW/RTTY... Well I live in South of France, so it is
easier for me ))

The reason why this antenna performs so well is that it incorporates
the tuning function in the large loop - the smaller loop does the
matching. In other words, the large loop wire and the capacitor will
reject signals that could overpower your radio and create AGC that
reduces its sensitivity. It is, in effect, a tuner as we have already
discussed. It also happens to be your antenna too.

But the first solution seems more efficient. Need to do further
investigations....

One point to consider, this large loop will not perform the same when
its diameter is large when compared to the wavelength you are tuning
to. Your longwire with tuner will probably be better in the 50M band
and higher. However, experimentation may prove different, especially
if you can tip the loop over (or change its angle to earth).

73's
Richard Clark, KB7QHC

On 12 dic, 00:28, Sébastien MEDARD wrote:
Hello,

On Fri, 10 Dec 2010 06:15:51 -0800, Wimpie wrote:

it may result in worse
reception because of overloading electronic circuits in your receiver.

OK for that.

If your balcony has a metal fence (that may be connected to rebar also),
you can use this as a ground provision for a wire antenna of about 5…
10m.

I didn't test that until now. I will.

Adding a 9:1 transformer (outside, directly below the antenna) will
increase antenna output at the lower bands. This does not automatically
mean that your S/N ratio increases also.

Portable receivers may experience overload. A preselector may help.
http://www.tetech.nl/divers/SimplePr...tor2.jpg*shows an (old) example.

I better see what could be a home made tuner. Seems quite easy to
build )

This one tunes from 3.3 to 26 MHz. By changing the crocodile clips, you
can perform some matching to get more output from the antenna, and
change the bandwidth of the preselection.

The crocodile clips can be replaced by a selector. Am I OK on that?

Correct, you can use two selectors instead of the clips.


For the lower bands (AM broadcast) a loop may have advantage.
Figure 2(a) in
http://www.compliance-club.com/archi...30718.htmshows the
construction of a loop out of coaxial cable. These types of loops have
built-in balanced to coaxial transition. *A square or circle of about 1m
(diameter) is a good start for the AM BC band.

It is called a shielded loop. Am I wrong?

Correct. To have the balun function, the cut in the shield must be
opposite to the position where the feeder leaves the loop.


Be careful with (expensive) loop antennas. If you can't get reception
with a simple well-constructed (tuned) loop because of local
interference (noise), the most expensive loop will not change that.

For now, I tried a lot of different things... The best result were on
loops.

A big loop (1.6mx4 = *6.4 meters), one turn, with an air variable
capacitor + an inside loop connected to the coaxial cable seems to give
better ways to give something to eat to my receiver. Sometimes my air
capacitor was not powerful enough, in the lower bands if I remember
well... To improve that I will have to add a fixed capacitor (lets say
300pF) in parallel (to be bypassed) or more depending on the band I am
listening to. For now I am just experimenting (with some simple wire),
but I think I will build a more solid one...

A big loop (1.6mx4 = *6.4 meters), one turn, with the the universal balun
from Wellbrook. Don't know why, but, it gives very good results, far
better than a long wire in my flat, or a short wire on my balcony... At
this time it seems there is a Ham Contest in Italia... I can get them
fully on 80m LSB/CW/RTTY... Well I live in South of France, so it is
easier for me ))

My experience is that at the lower bands (AM BC up to 3.6 MHz), loops
show better S/N ratio. However for the higher bands, performance
becomes similar to dipoles or monopoles. For reception I like the
small loops, as you can rotate them easily. They give less output,
but here tuning (even tuning inside close to the receiver) will
improve output (and noise….).

Regarding the large resonant loop with inside coupling loop, yes that
works well. I have a small one (0.6*0.4m) that tunes on the ham bands
from 3.6 to 30 MHz, it uses additional fixed capacitance for the lower
bands.
Unless you live in a very quiet environment, you can reduce the size
without sacrificing S/N ratio.



But the first solution seems more efficient. Need to do further
investigations....

Sebastien.

Best regards,


Wim
PA3DJS
www.tetech.nl

On Sat, 11 Dec 2010 16:21:29 -0800, Richard Clark wrote:

On 11 Dec 2010 23:28:18 GMT, Sébastien MEDARD wrote:

For now, I tried a lot of different things... The best result were on
loops.

Hi Sebastien,

This is a good lesson.

Thanks. I think I will try long wire again... I don't like to give up
without fighting a little bit. But perhaps I will try it outdoor putting
my receiver in the car outside any city or in a place where I get some
place. So everything about antenna tuners need more investigation.

A big loop (1.6mx4 = 6.4 meters), one turn, with an air variable
capacitor + an inside loop connected to the coaxial cable seems to give
better ways to give something to eat to my receiver.

This is an excellent antenna for BCB and Tropical Bands.

The problem seems to be related to wave propagation... I need to test
that a little bit more but... It is easier to receive radio broadcast
during the night. I need to know what are the differences between night/
day for wave propagation. What should I listen during the night and what
I should better listen during daylight...

I need to know a little bit more about digital transmission modes... To
be able to recognize digital patterns (on the waterfall display) to be
able apply the good settings for decoding... Easy for CW... Easy for RTTY
used by HAM... But what is the pattern for Meteo Faxes for example...?

By the way... I searched for good free software to decode meteo faxes...
But it seems not easy to find something free and easy to use... Do you
know shere I could find something interesting?

Sometimes my air
capacitor was not powerful enough, in the lower bands if I remember
well... To improve that I will have to add a fixed capacitor (lets say
300pF) in parallel (to be bypassed) or more depending on the band I am
listening to.

This is a great solution.

This is something I found on a website.... When you don't know anything
about electronics... Your learning curve is quite flat ))

For now I am just experimenting (with some simple wire), but I think I
will build a more solid one...

A big loop (1.6mx4 = 6.4 meters), one turn, with the the universal
balun from Wellbrook. Don't know why, but, it gives very good results,
far better than a long wire in my flat, or a short wire on my balcony...
At this time it seems there is a Ham Contest in Italia... I can get them
fully on 80m LSB/CW/RTTY... Well I live in South of France, so it is
easier for me ))

One point to consider, this large loop will not perform the same when
its diameter is large when compared to the wavelength you are tuning to.
Your longwire with tuner will probably be better in the 50M band and
higher.

I need to make a tuner first... Then I will tell you about it.

However, experimentation may prove different, especially if you
can tip the loop over (or change its angle to earth).

Well.... not so easy for now... My "experimentation board" is a big wood
shelf with a lot of books on it... Not so easy to flip, rotate or.... But
it is well oriented (east-west)

My next tries will be on a multiple turns loops. With or without matching
loop inside. I will try with simple wire but connection ribbon cables
could be a good alternative... (like old hard drive ribbon cable)

I was wondering... It seems loop antennas are a never ending story. As
far as I know, it seems there is no book that makes a good overview of
the different loop designs, with accessible schematics for preamp or
tuning stuff, how to avoid QRMs... There could be a very interesting area
both for SWL and HAM...

Perhaps the "Joe Carr's Loop Antenna Handbook" may be interesting, but it
is quite expensive and an Amazon reviewer says it is not so
interesting... What about the "Joe Carr's Receiving Antenna Handbook" ?

Sebastien.

On 12 Dec 2010 13:59:06 GMT, Sébastien MEDARD wrote:

The problem seems to be related to wave propagation... I need to test
that a little bit more but... It is easier to receive radio broadcast
during the night. I need to know what are the differences between night/
day for wave propagation. What should I listen during the night and what
I should better listen during daylight...

Hi Sébastien,

What you are talking about is common to DXing. Get yourself a globe
of the world. Light it up with an artificial "sun." The edge of the
dark/light should be half way between you and the transmitter you want
to hear. So, during the late day, your best signals are probably from
Eastern Europe, Turkey, and Asia. During the early-to-late night,
your best signals are probably from the Americas. During the late
afternoon to early evening you best signals are from the south or the
north.

I need to know a little bit more about digital transmission modes... To
be able to recognize digital patterns (on the waterfall display) to be
able apply the good settings for decoding... Easy for CW... Easy for RTTY
used by HAM... But what is the pattern for Meteo Faxes for example...?

When I used to teach RTTY there were only two tones. If modem
technology is any indication, that number has been raised and phase is
important.

By the way... I searched for good free software to decode meteo faxes...
But it seems not easy to find something free and easy to use... Do you
know shere I could find something interesting?

Nope.

My next tries will be on a multiple turns loops. With or without matching
loop inside. I will try with simple wire but connection ribbon cables
could be a good alternative... (like old hard drive ribbon cable)

This will reveal the "Law of Diminishing Returns" (the more you add,
the less you get back).

I was wondering... It seems loop antennas are a never ending story. As
far as I know, it seems there is no book that makes a good overview of
the different loop designs, with accessible schematics for preamp or
tuning stuff, how to avoid QRMs... There could be a very interesting area
both for SWL and HAM...

Oh, I am sure there are many such books gathering dust on shelves.
Loops have been around for more than a century, and if they were such
a good idea, then everyone would be using them.

Well, at one time they were a good idea, and EVERYONE used them - when
we had transistor pocket radios with analog tuning. The ferrite
antenna was the king of antennas for the vast majority of radio
owners. Before the transistor radio and ferrites, every table radio
had a flat pancake loop antenna in the back of the radio behind all
the glowing tubes.

Oddly enough, no radios in this age have either of these antennas
anymore, and they still seem to pick up stations.

So, there you have a century of technical perspective on the topic.

Perhaps the "Joe Carr's Loop Antenna Handbook" may be interesting, but it
is quite expensive and an Amazon reviewer says it is not so
interesting... What about the "Joe Carr's Receiving Antenna Handbook" ?

He is a respected author. I always look at the bad Amazon reviews to
see if something is terribly wrong with the product or terribly wrong
with the customer. Quite often the customer is disappointed because
that customer is stupid. If I encounter a smart customer that is
disappointed, I can well imagine all the good comments are not very
reliable.

The thing about all these -um- books is that many of them serve up old
wives' tales about low noise and other magical characteristics.
Remember the lessons of a century worth of experience with loop
antennas within an inch of the guts of any radio. That worked fine
for a billion radios and radios were not bought if they were "noisy."

The real science of low noise is found in the distance to the source.
Quite often it is your neighbor's aquarium heater that is noisy (the
most often complained of source of noise reported here). Your loop
sits in your shack and that aquarium is 10 Meters away. You switch to
your longwire that runs to the fence and the aquarium is 1 meter away.
Do I have to work out the math on that? Is the loop quieter because
of its magic design - or simply because it is 10 times further away
(20dB) from the noise?

We get writers here who pound the table because their magic loop in
the shack is noisy and their long wire 10M away in the back yard is
quiet. They have to be told to turn off the flourescent light in the
shack if they want their magic loop to work.
(Their magic loop low score on Amazon) = (stupid.)

73's
Richard Clark, KB7QHC

On Sun, 12 Dec 2010 12:25:59 -0800, Richard Clark wrote:

On 12 Dec 2010 13:59:06 GMT, Sébastien MEDARD wrote:

What you are talking about is common to DXing. Get yourself a globe of
the world. Light it up with an artificial "sun." The edge of the
dark/light should be half way between you and the transmitter you want
to hear. So, during the late day, your best signals are probably from
Eastern Europe, Turkey, and Asia. During the early-to-late night, your
best signals are probably from the Americas. During the late afternoon
to early evening you best signals are from the south or the north.

I understand better what is the purpose of this kind of map (on SDR-
Radio.com software for example). Where you can see an OM, you are pretty
sure to see this kind of map.

I need to know a little bit more about digital transmission modes... To
be able to recognize digital patterns (on the waterfall display) to be
able apply the good settings for decoding... Easy for CW... Easy for
RTTY used by HAM... But what is the pattern for Meteo Faxes for
example...?

When I used to teach RTTY there were only two tones.

The reason why they call you OM ? )

By the way... I searched for good free software to decode meteo faxes...
But it seems not easy to find something free and easy to use... Do you
know shere I could find something interesting?

Nope.

OK. I will try that later... For now I get some problems to use Linrad
with the SDR-IQ... Painful to boot on windows every time I want to listen
to shortwaves... And using a virtual system is not very efficient on my
old computer...

My next tries will be on a multiple turns loops. With or without
matching loop inside. I will try with simple wire but connection ribbon
cables could be a good alternative... (like old hard drive ribbon cable)

This will reveal the "Law of Diminishing Returns" (the more you add, the
less you get back).

Interesting. What would be the best ratio?

I was wondering... It seems loop antennas are a never ending story.

So, there you have a century of technical perspective on the topic.

)

Perhaps the "Joe Carr's Loop Antenna Handbook" may be interesting, but
it is quite expensive and an Amazon reviewer says it is not so
interesting... What about the "Joe Carr's Receiving Antenna Handbook" ?

He is a respected author. I always look at the bad Amazon reviews to
see if something is terribly wrong with the product or terribly wrong
with the customer. Quite often the customer is disappointed because
that customer is stupid. If I encounter a smart customer that is
disappointed, I can well imagine all the good comments are not very
reliable.

I will try to find one when they are cheaper.

The thing about all these -um- books is that many of them serve up old
wives' tales about low noise and other magical characteristics. Remember
the lessons of a century worth of experience with loop antennas within
an inch of the guts of any radio. That worked fine for a billion radios
and radios were not bought if they were "noisy."

OK. But today we probably ask more to radios than yesterday, no?

The real science of low noise is found in the distance to the source.

Lapalisse would have said exactly the same thing. He would have said that
the real science of good reception is found in the distance to the source
too )

Is the loop quieter because of its
magic design - or simply because it is 10 times further away (20dB) from
the noise?

OK for that.

We get writers here who pound the table because their magic loop in the
shack is noisy and their long wire 10M away in the back yard is quiet.
They have to be told to turn off the flourescent light in the shack if
they want their magic loop to work.
(Their magic loop low score on Amazon) = (stupid.)

Lesson one = learned.

Thanks.

Sebastien.

On Dec 13, 3:01*pm, Sébastien MEDARD wrote:


We get writers here who pound the table because their magic loop in the
shack is noisy and their long wire 10M away in the back yard is quiet.
They have to be told to turn off the flourescent light in the shack if
they want their magic loop to work.
* *(Their magic loop low score on Amazon) = (stupid.)

Lesson one = learned.

Thanks.

Sebastien.

One thing handy about a small loop is you can turn it to
null out the offending noise. Like Richard says, there is no
magical quality which provides lower noise vs any other
antenna. The real benefit is being about to turn it, usually
while in the listening position. If the loop is well balanced,
the nulls are quite sharp and deep and in many cases you
could make that nasty noise source vanish. You can also
turn it to receive multiple stations that are on the same
frequency. You null the one you want to get rid of.
But these type of loops are best suited for the low bands.
LW, MW are where they are best suited. You get much
better nulls off a ground wave signal, than you do one
that is propagated via skywave. So they tend to work
better at nulls in the daytime vs at night. At night, you
get a mix of ground and sky wave, and the nulls are not
as deep. In the day, I can make most ground wave
signals totally vanish by nulling them out.
These can be used in the SW bands, but don't expect
the deep nulls, being as most all SW will come via sky wave.
For general SWL, you are usually better off with the various
wire antennas. Random wires, dipoles, etc..
But I recommend a small loop for MW if you want the
ability to null noise or undesired stations.
Most of mine, I build from PVC tubing for the frames.
I have one in this room that is a diamond, 42 inches
per side. It's on a stand which allows it to rotate, and
it stands almost as tall as the ceiling. But they don't
have to be that big. I've got another round one that is
about 16 inches across, and it works very well too.
Just a tad less signal than the big one. But the s/n
ratio is much the same for the majority of the stations
listened to.
http://home.comcast.net/~nm5k/loop5.jpg
This is my usual favored method for building a low cost
MW loop. The hardest part to come by these days is
the variable cap. I dig them out of old radios, and old
analog tuning stereo receivers. Those are some of
the best ones to use, as they often have several
gangs which can be wired in parallel for more
capacitance, or deleted for less. For the upper
tuning ranges of the loop, it's best to delete most
of the gangs, and use one of the very small ones
by itself.
That way you get a smaller value, and will increase
the upper tuning range, vs just turning all the gangs
in parallel to the minimum setting. So I use switches
to do this quickly.
But if you can't find any old radios to acquire the
variable caps, you can buy them online from a few
places. I wouldn't use one any less than a dual
365pf BC cap. You can wire the two gangs together
for 730 pf. With careful loop turn design, you can
usually cover the whole MW BC band with one of
those. But I prefer the ones out of old stereo receivers.
They are even better, and can give a wider tuning
range. I think the one on my big loop has four or
five gangs, some being small and useful for upper
end tuning, if the other larger gangs are switched out.

On 13 Dec 2010 21:01:30 GMT, Sébastien MEDARD wrote:

I understand better what is the purpose of this kind of map (on SDR-
Radio.com software for example). Where you can see an OM, you are pretty
sure to see this kind of map.

Hi Sébastien,

If you mean the "gray line" map - yes.

When I used to teach RTTY there were only two tones.

The reason why they call you OM ? )

Touché

This will reveal the "Law of Diminishing Returns" (the more you add, the
less you get back).

Interesting. What would be the best ratio?

You mean the best number of turns? Depending upon band, maybe as many
as 6 to 10. One is good enough. There are many options to balance.
One correspondent here, years ago (silent key), wrote extensively on
this subject - google this group (or the internet) for Reg Edwards,
G4FGQ. For instance, google the keywords in:

RJELOOP1 *
Performance of Transceiving, single-turn, magloop antennas of various
regular shapes.

RJELOOP2 *
Performance of Transceiving, single-turn, magloop antennas of
rectangular shape.

RJELOOP3 *
Analysis of receiving, multi-turn, square, loop (or frame) antennas,
ELF to HF.

I will try to find one when they are cheaper.

Try:
http://www.bookfinder.com/search/?au...ic&st=sr&ac=qr

OK. But today we probably ask more to radios than yesterday, no?

No, probably less. Being an OM, (40 years ago) I also taught classes
for repair and maintenance of Collins' famous receiver, the R-390.
EVEN NOW (40 years later), this is probably the best receiver for its
price (and even two to three times its price).

The real science of low noise is found in the distance to the source.

Lapalisse would have said exactly the same thing. He would have said that
the real science of good reception is found in the distance to the source
too )

So, my comment was a lapalissade? Certainly.

73's
Richard Clark, KB7QHC

On 13 dic, 22:01, Sébastien MEDARD wrote:
On Sun, 12 Dec 2010 12:25:59 -0800, Richard Clark wrote:
On 12 Dec 2010 13:59:06 GMT, Sébastien MEDARD wrote:

What you are talking about is common to DXing. *Get yourself a globe of
the world. *Light it up with an artificial "sun." *The edge of the
dark/light should be half way between you and the transmitter you want
to hear. *So, during the late day, your best signals are probably from
Eastern Europe, Turkey, and Asia. *During the early-to-late night, your
best signals are probably from the Americas. *During the late afternoon
to early evening you best signals are from the south or the north.

I understand better what is the purpose of this kind of map (on SDR-
Radio.com software for example). Where you can see an OM, you are pretty
sure to see this kind of map.

I need to know a little bit more about digital transmission modes... To
be able to recognize digital patterns (on the waterfall display) to be
able apply the good settings for decoding... Easy for CW... Easy for
RTTY used by HAM... But what is the pattern for Meteo Faxes for
example...?

When I used to teach RTTY there were only two tones.

The reason why they call you OM ? )

By the way... I searched for good free software to decode meteo faxes....
But it seems not easy to find something free and easy to use... Do you
know shere I could find something interesting?

Nope.

OK. I will try that later... For now I get some problems to use Linrad
with the SDR-IQ... Painful to boot on windows every time I want to listen
to shortwaves... And using a virtual system is not very efficient on my
old computer...

My next tries will be on a multiple turns loops. With or without
matching loop inside. I will try with simple wire but connection ribbon
cables could be a good alternative... (like old hard drive ribbon cable)

This will reveal the "Law of Diminishing Returns" (the more you add, the
less you get back).

Interesting. What would be the best ratio?

I was wondering... It seems loop antennas are a never ending story.

So, there you have a century of technical perspective on the topic.

)

Perhaps the "Joe Carr's Loop Antenna Handbook" may be interesting, but
it is quite expensive and an Amazon reviewer says it is not so
interesting... What about the "Joe Carr's Receiving Antenna Handbook" ?

He is a respected author. *I always look at the bad Amazon reviews to
see if something is terribly wrong with the product or terribly wrong
with the customer. *Quite often the customer is disappointed because
that customer is stupid. *If I encounter a smart customer that is
disappointed, I can well imagine all the good comments are not very
reliable.

I will try to find one when they are cheaper.

The thing about all these -um- books is that many of them serve up old
wives' tales about low noise and other magical characteristics. Remember
the lessons of a century worth of experience with loop antennas within
an inch of the guts of any radio. *That worked fine for a billion radios
and radios were not bought if they were "noisy."

OK. But today we probably ask more to radios than yesterday, no?

The real science of low noise is found in the distance to the source.

Lapalisse would have said exactly the same thing. He would have said that
the real science of good reception is found in the distance to the source
too )

Is the loop quieter because of its
magic design - or simply because it is 10 times further away (20dB) from
the noise?

OK for that.

We get writers here who pound the table because their magic loop in the
shack is noisy and their long wire 10M away in the back yard is quiet.
They have to be told to turn off the flourescent light in the shack if
they want their magic loop to work.
* *(Their magic loop low score on Amazon) = (stupid.)

Lesson one = learned.

Thanks.

Sebastien.

Hello Sébastien,

Regarding tuning, loops and (long) wires.

You probably locate your antenna far away from noise sources. Mostly
this is not where your receiver is.

In case of tuned loops, you have to go outside for each significant
frequency change. This is one of the reasons that I want my
preselection / tuning adjacent to the receiver.

Loops aren't magic things. A wire from your balcony to a tree or other
tie point may give better S/N ratio then the best (expensive) loop on
your balcony.

Best matching isn't required for reception at HF, just sufficient
signal. In case of a PI tuning / preselector device, you need to
adjust two capacitors in case of major frequency change. In my
opinion a single capacitor device is more pleasant to use.

(deep) Nulls in the radiation pattern at low frequency (AM BC and
below) are the main benefit of the loop if you are willing to change
the orientation frequently when tuning across the bands. At increasing
frequency, the nulls are less pronounced because of propagation
issues. Off course a small horizontally oriented dipole has also
figure-of-eight radiation pattern, but polarization isn't good for AM
BC and lower.

For experimentation / comparison, I used a 1m diameter non-tuned loop
in the attic with preselection / tuning adjacent to the receiver. In
most cases a 5 m outdoor wire with same preselector and receiver gives
similar or better S/N ratio. This may be because of the attic has
mains wiring and I didn't want to go to the attic for reorientation
of the loop.

If you want to experiment with some long wire (unbalanced) antennas,
make sure to have a ground (counterpoise) provision outside; otherwise
your coaxial cable will be part of the antenna. This may result in
more interference from indoor sources.

Whether or not you have sufficient signal from your antenna is easy to
check. Listen to a known station. Tune your preselector to maximum
signal. Now tune to a free frequency close to your station's frequency
so that you hear noise. Remove the antenna, the audio noise should be
less now.

If you use a tapped coil preselector (like the one in my link), and
have sufficient noise from the antenna, you may even change the taps.
The preselector will give more insertion loss, but it will be more
selective also. This can be of use when you have strong signals in
your neighborhood. Because of portability, I frequently use an AOR
AR8200. Without preselection, such a wide band receiver is useless
with an external antenna.

Best regards,


Wim
PA3DJS
www.tetech.nl
without abc, PM will reach me very likely

On Mon, 13 Dec 2010 15:38:20 -0800, nm5k wrote:

On Dec 13, 3:01Â*pm, Sébastien MEDARD wrote:

One thing handy about a small loop is you can turn it to null out the
offending noise.

I should try small loops too.

You get much
better nulls off a ground wave signal, than you do one that is
propagated via skywave. So they tend to work better at nulls in the
daytime vs at night. At night, you get a mix of ground and sky wave, and
the nulls are not as deep. In the day, I can make most ground wave
signals totally vanish by nulling them out.

That's an interesting concept. The difference between ground and sky
waves and the way to use loops. And small loops are easier to make...

Most of mine, I build from PVC tubing for the frames.

A simple, but good idea. PVC tubing is inexpensive and quite rigid...

I have one in this room that is a diamond, 42 inches per side.

One meter... It is approximatively what I wanted to do at the beginning.

It's on a stand
which allows it to rotate, and it stands almost as tall as the ceiling.

Do you tune it, or not? Is there a small loop inside or not?

But they don't have to be that big. I've got another round one that is
about 16 inches across, and it works very well too. Just a tad less
signal than the big one. But the s/n ratio is much the same for the
majority of the stations listened to.

I definitively need to test them.

http://home.comcast.net/~nm5k/loop5.jpg This is my usual favored method
for building a low cost MW loop. The hardest part to come by these days
is the variable cap.

I got one and I am searching for others. It seems that variable caps are
one of the center of a lot of things in radio reception )

I can see on the loop5.jpg image that you connected one wire to the
ground and one wire to both other connections (double gang capacitor) so
that you add the result of both capacitors. Is that correct?

That way you get a smaller value, and will increase the upper tuning
range, vs just turning all the gangs in parallel to the minimum setting.
So I use switches to do this quickly.

Exact. That sounds good.

But if you can't find any old radios to acquire the variable caps, you
can buy them online from a few places. I wouldn't use one any less than
a dual 365pf BC cap. You can wire the two gangs together for 730 pf.

That's the kind I get.

With careful loop turn design, you can usually cover the whole MW BC
band with one of those. But I prefer the ones out of old stereo
receivers. They are even better, and can give a wider tuning range. I
think the one on my big loop has four or five gangs, some being small
and useful for upper end tuning, if the other larger gangs are switched
out.

I found a 500pF + 500pF one too, with a slow motion drive. Another way to
drive them slowly is to get a 20cm (10 inches) piece of wood, perforate
it on one side to put the capacitor axis into the hole (put some glue,
but a smaller hole is better, and push it hard so that the axis enters
inside the hole), and you get something that can be tune very precisely
with one finger... About the piece of wood, the longer, the higher in
precision tuning.

Sebastien.

On Mon, 13 Dec 2010 16:06:51 -0800, Richard Clark wrote:

On 13 Dec 2010 21:01:30 GMT, Sébastien MEDARD wrote:

I understand better what is the purpose of this kind of map (on SDR-
Radio.com software for example). Where you can see an OM, you are pretty
sure to see this kind of map.

Hi Sébastien,

If you mean the "gray line" map - yes.

There should free software displaying this gray line with UTC time, no?

This will reveal the "Law of Diminishing Returns" (the more you add,
the less you get back).

Interesting. What would be the best ratio?

You mean the best number of turns?

Economics is interesting too

RJELOOP3 *
Analysis of receiving, multi-turn, square, loop (or frame) antennas, ELF
to HF.

Can be find here :
http://www.zerobeat.net/G4FGQ/page3.html#S301

I will try to find one when they are cheaper.

Try:
http://www.bookfinder.com/search/?au...%27s+Receiving
+Antenna+Handbook&lang=en&isbn=&submit=Begin
+search&new_used=*&destination=us&currency=USD&mod e=basic&st=sr&ac=qr

I found the "Receiving Antenna Handbook" quite cheap, but the "Loop
Antenna Handbook" is still expensive. Between $60 to $257... I will try
the cheapest.

OK. But today we probably ask more to radios than yesterday, no?

No, probably less. Being an OM, (40 years ago) I also taught classes
for repair and maintenance of Collins' famous receiver, the R-390. EVEN
NOW (40 years later), this is probably the best receiver for its price
(and even two to three times its price).

Do you calculate that in constant dollar from the 50's?

I can imagine the teaching class. Everybody with a Collin's in front of
him/her... A one year project to restore completely one of this legendary
radio. I would like that!

With a good DSP outside (Audio DSP only), can beat every other ones?

It seems not easy to get one, especially in Europe...

The real science of low noise is found in the distance to the source.

Lapalisse would have said exactly the same thing. He would have said
that the real science of good reception is found in the distance to the
source too )

So, my comment was a lapalissade? Certainly.

You got the picture

Sebastien.