From: DK7FC <73dk7fc@googlemail.com>
Message-ID: <5543AC11.1070000@gmail.com>
Date: Fri, 01 May 2015 18:38:41 +0200
User-Agent: Mozilla/5.0 (Windows; U; Windows NT 6.1; de; rv:1.9.1.8) Gecko/20100227 Thunderbird/3.0.3
MIME-Version: 1.0
To: rsgb_lf_group@blacksheep.org
References: <579355A36AEE9D4FA555C45D556003AB1B0F416E@servigilant.vigilant.local> <553FFAC1.7060609@gmail.com> <E1Ynvp9-0002hY-Tv@post.thorcom.com>
In-Reply-To: <E1Ynvp9-0002hY-Tv@post.thorcom.com>
Subject: Re: LF: questions about a tx square loop fpr 470KHz
Content-Type: multipart/alternative;
 boundary="------------000606010603050708050806"
Sender: owner-rsgb_lf_group@blacksheep.org
Precedence: bulk
Reply-To: rsgb_lf_group@blacksheep.org
Status: O

This is a multi-part message in MIME format.
--------------000606010603050708050806
Content-Type: text/plain; charset=UTF-8; format=flowed
Content-Transfer-Encoding: 8bit

Hi Mauro,

Your shack seems to be on a high building, so a short vertical antenna 
would give you better results than such a loop.
If there is no way to install a vertical, only a loop, then do it! You 
will certainly make some 100 km distance with 20W!

I would use a single turn loop because the resonance curve will be very 
sharp for a 2 turn loop, so the mechanical construction must be very 
stable. 7m x 3m is not so bad. You may need 10 nF or so, for the 
resonance (a very rough guess, without any calculations).
Instead of 6mm^2 wire i would use a RG213/RG214 cable, or many of them! 
For the C is would use WIMA-FKP-1 2kV 2.2 nF types and solder a few of 
them in parallel. It is _most important _to keep the wires as lossless 
as possible, even a 1 cm piece of wire with 1mm diameter will cause 
significant losses. Smaller C values could be switched in parallel (they 
only have to carry a small part of the total current so the losses are 
small) to find the exact resonance
Like in my images of the 1m diameter loop i would use a big ferrite 
toroid to couple the TX/cable to the loop. Galvanic decoupling may be 
helpful to prevent EMC problems and it is the easiest way to match the 
system.
In my loop, the most lossy thing is the capacitor pack. They become warm 
at > 25W.

Yes, it is a good idea to start TXing in WSPR since your signal will be 
to weak for large CW distances and you will see reports giving an idea 
about the signal strength and direction...

Good luck!

73, Stefan

Am 30.04.2015 23:16, schrieb IK1WVQ Mauro:
>
> 73 to all,
>
> I would like to know your opinion about this:
>
> I can made a square TX loop for 470KHz of 7 * 3 meters (see picture) 
> in the terrace of the building where I live (6 floors).
>
> the questions are:
>
> - it is enough a 6mmq copper electric wire ??  (20W is the output 
> power of my tx).
> - single turn or two turns spaced 10cm max ?? (two turns =  less pF 
> required to take the resonance).
> - Is this a good idea to start to trasmit on 470KHz WSPR ??
>
> thanks in advance for your attention.
>
> 73 de Mauro IK1WVQ
>
>
>
> ------------------------------------------------------------------------
> Avast logo <http://www.avast.com/> 	
>
> Questa e-mail è stata controllata per individuare virus con Avast 
> antivirus.
> www.avast.com <http://www.avast.com/>
>
>

--------------000606010603050708050806
Content-Type: text/html; charset=UTF-8
Content-Transfer-Encoding: 8bit

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
  <meta content="text/html; charset=UTF-8" http-equiv="Content-Type">
</head>
<body bgcolor="#ffffff" text="#000000">
Hi Mauro, <br>
<br>
Your shack seems to be on a high building, so a short vertical antenna
would give you better results than such a loop. <br>
If there is no way to install a vertical, only a loop, then do it! You
will certainly make some 100 km distance with 20W!<br>
<br>
I would use a single turn loop because the resonance curve will be very
sharp for a 2 turn loop, so the mechanical construction must be very
stable. 7m x 3m is not so bad. You may need 10 nF or so, for the
resonance (a very rough guess, without any calculations).<br>
Instead of 6mm^2 wire i would use a RG213/RG214 cable, or many of them!
For the C is would use WIMA-FKP-1 2kV 2.2 nF types and solder a few of
them in parallel. It is <u>most important </u>to keep the wires as
lossless as possible, even a 1 cm piece of wire with 1mm diameter will
cause significant losses. Smaller C values could be switched in
parallel (they only have to carry a small part of the total current so
the losses are small) to find the exact resonance<br>
Like in my images of the 1m diameter loop i would use a big ferrite
toroid to couple the TX/cable to the loop. Galvanic decoupling may be
helpful to prevent EMC problems and it is the easiest way to match the
system. <br>
In my loop, the most lossy thing is the capacitor pack. They become
warm at &gt; 25W.<br>
<br>
Yes, it is a good idea to start TXing in WSPR since your signal will be
to weak for large CW distances and you will see reports giving an idea
about the signal strength and direction...<br>
<br>
Good luck!<br>
<br>
73, Stefan<br>
<br>
Am 30.04.2015 23:16, schrieb IK1WVQ Mauro:
<blockquote cite="mid:E1Ynvp9-0002hY-Tv@post.thorcom.com" type="cite"><br>
73 to all,<br>
  <br>
I would like to know your opinion about this:<br>
  <br>
I can made a square TX loop for 470KHz of 7 * 3 meters (see picture) in
the terrace of the building where I live (6 floors).<br>
  <br>
the questions are:<br>
  <br>
- it is enough a 6mmq copper electric wire ??  (20W is the output
power of my tx).<br>
- single turn or two turns spaced 10cm max ?? (two turns =  less pF
required to take the resonance).<br>
- Is this a good idea to start to trasmit on 470KHz WSPR ??<br>
  <br>
thanks in advance for your attention.<br>
  <br>
73 de Mauro IK1WVQ<br>
  <br>
  <br>
  <br>
  <hr
 style="border: medium none ; color: rgb(144, 144, 144); background-color: rgb(176, 176, 176); height: 1px; width: 99%;">
  <table style="border: medium none ; border-collapse: collapse;">
    <tbody>
      <tr>
        <td style="border: medium none ; padding: 0px 15px 0px 8px;"> <a
 moz-do-not-send="true" href="http://www.avast.com/"> <img
 moz-do-not-send="true"
 src="http://static.avast.com/emails/avast-mail-stamp.png"
 alt="Avast logo" border="0"> </a> </td>
        <td>
        <p
 style="color: rgb(61, 77, 90); font-family: &quot;Calibri&quot;,&quot;Verdana&quot;,&quot;Arial&quot;,&quot;Helvetica&quot;; font-size: 12pt;">
Questa e-mail è stata controllata per individuare virus con Avast
antivirus. <br>
        <a moz-do-not-send="true" href="http://www.avast.com/">www.avast.com</a>
        </p>
        </td>
      </tr>
    </tbody>
  </table>
  <br>
</blockquote>
</body>
</html>

--------------000606010603050708050806--