Hello,

I am a complete newbie in SWL.

At fourth floor (last one) of a building, I get a balcony where I could
put an antenna for ham and broadcast reception (SWL). Well the balcony is
quite small, but quite comfortable too

Now, I get a poor wire from my flat to the ground (near the ground). It
gives me some night reception for broadcast from 500 KHz to 1500 MHz (it
is quite interesting, but quite limited too...). Except that, I get
nothing. Frustrating.

I planned to build some loop antennas, but first of all, I wanted to
focus on long wire antennas.

Please, give me your thoughts:

I am about to build a long wire antenna, but something quite different...
Like hand-held receivers antennas, I want to wrap 100 meters of standard
wire around on a 4cm (diameter) plastic tube (like a slinky antenna).

I get three different ways to do that:
- like the standard long wire, feeder on one side with a 9:1 balun
- like a dipole (feeder at the center)
- like a 1/4 wave (vertical one) with the steel fence for the ground and
to hang up the plastic tube. The fence itself is grounded.

What do you think about this type of antenna?

What about the reception efficiency of each kind of solution for all
bands between 500 KHz to 30 MHz?

Tell me if it is interesting to test that or I should not lose my time
and begin building a loop antenna?

Thanks.

Sebastien.



In French :

Hello,

Ma situation est la suivante. Au 4ème et dernier étage d'un immeuble, je
dispose d'un balcon sur lequel disposer une antenne pour recevoir les
émission broadcast et les émissions radio-amateur en HF. Evidemment,
c'est assez petit quoiqu'assez confortable.

Pour le moment, un vague fil pendouillait par le balcon, ce dernier
m'offrant un peu de réception, de nuit entre 500 Hz et 1500 MHz (c'est
pas inintéressant, mais c'est limité....). Sorti de ça, je n'ai rien.
Fort sentiment de frustration.

J'ai en projet la réalisation d'une antenne loop, mais dans un premier
temps, je voudrais me concentrer sur le long fil.

J'aurais voulu avoir votre avis.

Je suis sur le point de construire une antenne de réception de type long
fil, mais modifiée... A l'image des antennes de réception des récepteurs
portables, je pensais bobiner une bonne longueur de fil (une centaine de
mètres) sur du tuyau PVC de diamètre 4cm (fil électrique de base,
bobinage Ã* spires jointives).

Trois possibilités s'offrent Ã* moi :
- Alimentation par une extrémité, le long fil classique, mais bobiné
- Alimentation au milieu en doublet 1/2 ondes, évidemment toujours bobiné
- Alimentation en quart d'onde, verticale (encore bobiné), en utilisant
la rambarde métallique comme terre (et comme support pour mon tube), la
rambarde faisant la longueur de l'immeuble (la rambarde étant elle-même
raccordée Ã* la terre).

Que pensez-vous du principe ?

Et que pensez-vous du rendement de chacune des solutions en HF toutes
bandes ?

Avec mes remerciements,

Sébastien.

On 07 Dec 2010 23:11:16 GMT, Sébastien MEDARD wrote:

Now, I get a poor wire from my flat to the ground (near the ground). It
gives me some night reception for broadcast from 500 KHz to 1500 MHz (it
is quite interesting, but quite limited too...). Except that, I get
nothing. Frustrating.

Hi Sebastien,

Use an antenna tuner (same thing Amateurs use, but without the
meters).

You probably need this because of the Broadcast transmitters. Those
transmitters can force your radio to create an AGC voltage even when
you are not tuned to the Broadcast frequency. This AGC voltage causes
your radio to lose sensitivity.

To put it another way, suppose:
you have a strong Broadcast station nearby on 1 MHz;
you connect your radio to a long antenna for SWL;
you tune to the 31M band;
the Broadcast signal creates a very strong AGC;
you (naturally) do not hear the Broadcast signal;
you (un-naturally) do not hear many 31M band signals.

To solve this:
Add a tuner;
you adjust it for the 31M band;
it removes the Broadcast signal;
your AGC voltage is now based on 31M band signals;
your radio becomes very sensitive;
you hear more 31M band signals.

This will also work for weak Broadcast signals.

73's
Richard Clark, KB7QHC

Hello,

On Tue, 07 Dec 2010 16:21:41 -0800, Richard Clark wrote:

On 07 Dec 2010 23:11:16 GMT, Sébastien MEDARD wrote:


To solve this: Add a tuner;

You cut corners I was thinking about adding a Tuner or maybe something
that is called preselector/tuner...

But, before that I just wanted to know what would be a good antenna, or
good antennas for where I live.

Thus, I was thinking about adapting the basics (long wire, dipole) to my
situation. What do you think about shorting a long wire to a big self?

Would this self work better adapted on one side, like a dipole or a
quarter of a wave?

By the way...... What would be a good antenna tuner for a SWL? Any advice
for a brand? Any advice for a good DIY kit?

Thanks.

Sebastien.

S?bastien MEDARD wrote:
By the way...... What would be a good antenna tuner for a SWL? Any advice
for a brand? Any advice for a good DIY kit?

Here's my suggestion. It's a combination pre-selector and amplifer:

http://rffun.com/catalog/preamps/2158.html

If you are handy with a soldering iron you can easily add a second receiver
output.

Geoff.
--
Geoffrey S. Mendelson N3OWJ/4X1GM
Those who cannot remember the past are condemned to misquote it.

On 08 Dec 2010 00:45:41 GMT, Sébastien MEDARD wrote:

But, before that I just wanted to know what would be a good antenna, or
good antennas for where I live.

Hi Sebastien,

The best is the one that will be as high as possible. Length should
be 5 to 10 meters. Orientation should be broadside to the stations
you want to listen to. You should have a choke (W2DU style BalUn)
connected at the feedpoint. One example shown at:
http://www.n0ss.net/qrp_1-1_w2du_coaxial_balun.pdf

You should think of more than one antenna (maybe one vertical, one
horizontal).

Paying attention to your ground is important, but if you live upstairs
in an apartment, then think dipole (even if one side is vertical -
where the horizontal wire would be called a "long-wire").

By the way...... What would be a good antenna tuner for a SWL? Any advice
for a brand? Any advice for a good DIY kit?

The price you could pay is not a predictor of performance. Look at
the schematic on the last page of:
http://www.mfjenterprises.com/man/pdf/MFJ-902.pdf
It can be built from parts for less than $100. It basically
represents the most flexible design, but there are other useful
designs. Even there, with a good switching design you could use the
same components to build them too. (I am thinking of PI
configuration, L, and so on).

Old AM (tube) radio parts are perfect for building your own tuner.

73's
Richard Clark, KB7QHC

Hello,

On Tue, 07 Dec 2010 21:58:17 -0800, Richard Clark wrote:

On 08 Dec 2010 00:45:41 GMT, Sébastien MEDARD wrote:

But, before that I just wanted to know what would be a good antenna, or
good antennas for where I live.

want to listen to. You should have a choke (W2DU style BalUn) connected
at the feedpoint. One example shown at:
http://www.n0ss.net/qrp_1-1_w2du_coaxial_balun.pdf

That's the first thing I will do. Ferrite ordered

Paying attention to your ground is important, but if you live upstairs
in an apartment, then think dipole (even if one side is vertical - where
the horizontal wire would be called a "long-wire").

OK.

By the way...... What would be a good antenna tuner for a SWL? Any
advice for a brand? Any advice for a good DIY kit?

The price you could pay is not a predictor of performance. Look at the
schematic on the last page of:
http://www.mfjenterprises.com/man/pdf/MFJ-902.pdf

Seems not so simple for me.

I see two things on the schematic :

- 2 variable capcitor and an inductance on the center
- A balun for balanced line (ie dipole????)

As I already get a balun for dipole could you confirm that I just need the
center part of the schematic?

If the answer is yes, if I understand the schematic well, both of
variable capacitors are put one after the other inserted into the line.
The big question is how to make the variable inductance? Some wire wired
on a ferrite rod? (L ----------- A????) with a selector? Are the number
of half-loops means the number of turns?

Even there, with a good
switching design you could use the same components to build them too.
(I am thinking of PI configuration, L, and so on).

What is the influence of these different configurations?

Old AM (tube) radio parts are perfect for building your own tuner.

It seems I need to find some

Thank you for your patience,

Sebastien.

On 09 Dec 2010 17:11:54 GMT, Sébastien MEDARD wrote:

http://www.n0ss.net/qrp_1-1_w2du_coaxial_balun.pdf

That's the first thing I will do. Ferrite ordered

Hi Sébastien,

Good first step.

http://www.mfjenterprises.com/man/pdf/MFJ-902.pdf

Seems not so simple for me.

I see two things on the schematic :

- 2 variable capcitor and an inductance on the center

Good.

- A balun for balanced line (ie dipole????)

Yes.

As I already get a balun for dipole could you confirm that I just need the
center part of the schematic?

Confirmed, yes.

If the answer is yes, if I understand the schematic well, both of
variable capacitors are put one after the other inserted into the line.
The big question is how to make the variable inductance? Some wire wired
on a ferrite rod? (L ----------- A????) with a selector? Are the number
of half-loops means the number of turns?

Making the coil is easy. It is just bare wire. You connect leads
between various turns in the coil and a switch. A three to five
position switch will work. You can even wind separate coils and put
them on the switch so they add up in series as you turn the switch.

Even there, with a good
switching design you could use the same components to build them too.
(I am thinking of PI configuration, L, and so on).

What is the influence of these different configurations?

Some antennas (I am speaking of their wavelength, not style like
horizontal, vertical, end-fed, or other) are easier to tune with these
other styles, but the style offered in the link is fairly general
purpose.

Old AM (tube) radio parts are perfect for building your own tuner.

It seems I need to find some

It may not be easy, but if you can find the right shop, you will find
many. Tell the shop owner you want this for experimentation and you
might get something that isn't in the shop display. The only thing
you really need is the variable capacitor from two radios. This
technology was very common and found in nearly every home in the 1950s
and 60s, but now would be rare unless you find that shop.

Thank you for your patience,

Feel free to ask more questions when it comes time to put this
together.

73's
Richard Clark, KB7QHC

On 8 dic, 00:11, Sébastien MEDARD wrote:
Hello,

I am a complete newbie in SWL.

At fourth floor (last one) of a building, I get a balcony where I could
put an antenna for ham and broadcast reception (SWL). Well the balcony is
quite small, but quite comfortable too

Now, I get a poor wire from my flat to the ground (near the ground). It
gives me some night reception for broadcast from 500 KHz to 1500 MHz (it
is quite interesting, but quite limited too...). Except that, I get
nothing. Frustrating.

I planned to build some loop antennas, but first of all, I wanted to
focus on long wire antennas.

Please, give me your thoughts:

I am about to build a long wire antenna, but something quite different...
Like hand-held receivers antennas, I want to wrap 100 meters of standard
wire around on a 4cm (diameter) plastic tube (like a slinky antenna).

I get three different ways to do that:
- like the standard long wire, feeder on one side with a 9:1 balun
- like a dipole (feeder at the center)
- like a 1/4 wave (vertical one) with the steel fence for the ground and
to hang up the plastic tube. The fence itself is grounded.

What do you think about this type of antenna?

What about the reception efficiency of each kind of solution for all
bands between 500 KHz to 30 MHz?

Tell me if it is interesting to test that or I should not lose my time
and begin building a loop antenna?

Thanks.

Sebastien.

In French :

Hello,

Ma situation est la suivante. Au 4ème et dernier étage d'un immeuble, je
dispose d'un balcon sur lequel disposer une antenne pour recevoir les
émission broadcast et les émissions radio-amateur en HF. Evidemment,
c'est assez petit quoiqu'assez confortable.

Pour le moment, un vague fil pendouillait par le balcon, ce dernier
m'offrant un peu de réception, de nuit entre 500 Hz et 1500 MHz (c'est
pas inintéressant, mais c'est limité....). Sorti de ça, je n'ai rien.

On Thu, 09 Dec 2010 11:33:27 -0800, Richard Clark wrote:

If the answer is yes, if I understand the schematic well, both of
variable capacitors are put one after the other inserted into the line.
The big question is how to make the variable inductance? Some wire wired
on a ferrite rod? (L ----------- A????) with a selector? Are the number
of half-loops means the number of turns?

Making the coil is easy. It is just bare wire. You connect leads
between various turns in the coil and a switch. A three to five
position switch will work. You can even wind separate coils and put
them on the switch so they add up in series as you turn the switch.

OK.

Even there, with a good
switching design you could use the same components to build them too.
(I am thinking of PI configuration, L, and so on).

What is the influence of these different configurations?

Some antennas (I am speaking of their wavelength, not style like
horizontal, vertical, end-fed, or other) are easier to tune with these
other styles, but the style offered in the link is fairly general
purpose.

I found a PI network tuner shematic.

Many thanks for the first steps help!

Sébastien.

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.
www.tetech.nl/divers/SimplePreselector2.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?

For the lower bands (AM broadcast) a loop may have advantage.

Figure 2(a) in
http://www.compliance-club.com/archi...ive/030718.htm shows 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?

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 ))

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

Sebastien.