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 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.