Mainflingen MW cross dipole antenna 4EN

<body topmargin=0 leftmargin=0 marginheight=0 marginwidth=0> <table cellpadding=0 cellspacing=0 border=0><tr> <td valign="top" height=50 BGCOLOR="#0099FF" TEXT="#F7F7FF"> <div> <FONT SIZE="4" COLOR="#FFFFFF" FACE="Arial" ><B>Bernd Waniewski - http://www.waniewski.de</B></FONT><B>     |     </B><A HREF="http://www.waniewski.de/index.htm" TARGET="_top" TITLE="http://www.waniewski.de/index.htm"><U><B>Startseite</B></U></A><B>   </B><A HREF="http://www.waniewski.de/id208.htm" TARGET="_top" TITLE="http://www.waniewski.de/id208.htm"><U><B>Home </B></U></A><B>  </B><A HREF="http://www.waniewski.de/id207.htm" TARGET="_top" TITLE="http://www.waniewski.de/id207.htm"><U><B>Acceuil</B></U></A></div> <bR> <div> </div> </td> </tr><tr> <td valign="top" height=430 BGCOLOR="#FFFFFF" TEXT="#080000"> <div> Mainflingen MW cross dipole antenna   4EN</div> <div> <TABLE BORDER="1" CELLPADDING="6" CELLSPACING="1" WIDTH="865" BORDERCOLORLIGHT="#FFCC66" BORDERCOLORDARK="#FFFFFF" FRAME="BOX" RULES="ALL" 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><B>4</B></FONT><B>  </B><A HREF="id333.htm" TARGET="_top" TITLE="Mainflingen MW cross dipole antenna 5E"><U><B>5</B></U></A><B>  </B><A HREF="id334.htm" TARGET="_top" TITLE="Mainflingen MW cross dipole antenna 6E"><U><B>6</B></U></A><B>  </B><A HREF="id336.htm" TARGET="_top" TITLE="Mainflingen MW cross dipole antenna 7E"><U><B>7</B></U></A><B>  </B><A HREF="id337.htm" TARGET="_top" TITLE="Mainflingen MW cross dipole antenna 8E"><U><B>8</B></U></A></div> </tD> <tD VALIGN=TOP><NOBR><div> <A HREF="id312.htm" TARGET="_top" TITLE="Mainflingen MW Kreuzdipol 4DE"><U><IMG SRC="a94331f0.gif" border=0 width="51" height="31" ALIGN="BOTTOM" HSPACE="0" VSPACE="0"></U></A></div> <div> <A HREF="id312.htm" TARGET="_top" TITLE="Mainflingen MW Kreuzdipol 4DE"><U>German</U></A></div> </NOBR></tD> <tD VALIGN=TOP BGCOLOR=#FFCC66 WIDTH="81"><div> <A HREF="http://www.waniewski.de/id208.htm" TARGET="_top" TITLE="http://www.waniewski.de/id208.htm"><U><B>Home</B></U></A></div> </tD> <tD VALIGN=TOP ROWSPAN=2 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HREF="http://www.waniewski.de/id208.htm#all_english_versions_of_antenna_sites" TARGET="_top" TITLE="http://www.waniewski.de/id208.htm#all_en"><U> A-Z</U></A></div> </NOBR></tD> <tD VALIGN=TOP BGCOLOR=#FFCC66 WIDTH="81"><div> <A HREF="http://www.waniewski.de/id208.htm#all_projekts_by_list_of_frequencies" TARGET="_top" TITLE="http://www.waniewski.de/id208.htm#all_pr"><U>Projects by</U></A></div> <div> <A HREF="http://www.waniewski.de/id208.htm#all_projekts_by_list_of_frequencies" TARGET="_top" TITLE="http://www.waniewski.de/id208.htm#all_pr"><U> list of frequencies</U></A></div> </tD> </tR> </TABLE></div> <div> <TABLE BORDER="1" CELLPADDING="6" CELLSPACING="1" WIDTH="864" BORDERCOLORLIGHT="#FFCC66" BORDERCOLORDARK="#FFFFFF" FRAME="BOX" RULES="ALL" ALIGN="BOTTOM" HSPACE="0" VSPACE="0" BGCOLOR=#FFFFCC > <tR> <tD VALIGN=TOP COLSPAN=2 HEIGHT= 38 WIDTH="461"><div> MW Mainflingen cross dipole antenna  - </div> <div> antenna tuning hut and feeding cables</div> </tD> <tD VALIGN=TOP BGCOLOR=#FFCC66><NOBR><div> <B>Technical description</B> (continued from <FONT SIZE="3" COLOR="#0000FF" FACE="Arial" ><A HREF="id331.htm" TARGET="_top" TITLE="Mainflingen MW cross dipole antenna 2E"><U><B>2E</B></U></A></FONT><B>):</B></div> </NOBR></tD> </tR> <tR> <tD VALIGN=TOP COLSPAN=2 BGCOLOR=#FFCC66 HEIGHT= 345 ><NOBR><div> <IMG SRC="716c4530.jpg" border=0 width="452" height="339" ALIGN="BOTTOM" HSPACE="0" VSPACE="0"></div> </NOBR></tD> <tD VALIGN=TOP BGCOLOR=#FFFFCC WIDTH="358"><div> Every dipole is fed via a power cable of 5" (characteristic impedance 75 ohms) which leads vertically from the base of the centre mast (see photo left) to the feeding point of the dipole on top of the mast at the height of appr. 80 m. </div> <div> A design was to be found in order to allow the tuning of the impedance at feeding point of the dipole. This impedance should correspond as close as possible to characteristic impedance of the cable.</div> <div> At the same time it was necessary to provide a balun for the symmetrical dipole and the unsymmetrical cable. Both tuning and baluning were realized by a stub (a short circuited line) connected to the feeding point at the dipole and consisting of the feeder cable and a rigid tubular line. </div> <bR> <bR> </tD> </tR> <tR> <tD VALIGN=TOP BGCOLOR=#FFCC66 HEIGHT= 243 ><NOBR><div> <IMG SRC="718b2ed0.jpg" border=0 width="178" height="237" ALIGN="BOTTOM" HSPACE="0" VSPACE="0"></div> </NOBR></tD> <tD VALIGN=TOP BGCOLOR=#FFCC66><NOBR><div> <IMG SRC="7670dec0.jpg" border=0 width="269" height="236" ALIGN="BOTTOM" HSPACE="0" VSPACE="0"></div> </NOBR></tD> <tD VALIGN=TOP ROWSPAN=2 BGCOLOR=#FFFFCC WIDTH="358"><div> Feeder cable and a rigid tubular line are in parallel and fixed to the mast by means of insulators. ( see photo ) </div> <div> The length of the stub allows the transformation of impedance. The stub represents a parallel inductance to the feeding point of the dipole transforming the antenna impedance close to characteristic impedance of the cable (75 ohms).  </div> <div> The dimension of length and width of the dipoles was also carefully chosen in order  to obtain an atenna sytem where the dipole impedance is nearly equal to the characteristic impedance of the cable (75 ohms). </div> </tD> </tR> <tR> <tD VALIGN=TOP BGCOLOR=#FFFFCC HEIGHT= 33 WIDTH="182"><div> grounding of feeding cable to mast</div> </tD> <tD VALIGN=TOP BGCOLOR=#FFFFCC WIDTH="276"><div> Stub (Carter loop) at the feeding point of dipole consisting of rigid tubular line and feeding cable. </div> </tD> </tR> <tR> <tD VALIGN=TOP COLSPAN=2 BGCOLOR=#FFCC66 HEIGHT= 353 ><NOBR><div> <IMG SRC="f81ce5b0.jpg" border=0 width="462" height="347" ALIGN="BOTTOM" HSPACE="0" VSPACE="0"></div> </NOBR></tD> <tD VALIGN=TOP BGCOLOR=#FFFFCC WIDTH="358"><div> <B>The stub</B></div> <bR> <div> The stub consists of the cable and the tube. It is fixed to the mast by means of insulators.</div> <bR> <bR> <bR> <bR> <bR> <bR> <bR> <bR> <div> photo: T-Systems</div> </tD> </tR> <tR> <tD VALIGN=TOP COLSPAN=2 BGCOLOR=#FFCC66 HEIGHT= 353 ><NOBR><div> <IMG SRC="f83cf5b0.jpg" border=0 width="463" height="347" ALIGN="BOTTOM" HSPACE="0" VSPACE="0"></div> </NOBR></tD> <tD VALIGN=TOP BGCOLOR=#FFFFCC><NOBR><div> The clamp for fastening the cable to the insulator.</div> <bR> <div> Gerhard Baumbach inspecting all details.</div> <bR> <bR> <bR> <bR> <bR> <bR> <bR> <bR> <bR> <div> photo: T-Systems</div> </NOBR></tD> </tR> <tR> <tD VALIGN=TOP COLSPAN=2 BGCOLOR=#FFCC66 HEIGHT= 354 ><NOBR><div> <IMG SRC="d8ed05c0.jpg" border=0 width="464" height="348" ALIGN="BOTTOM" HSPACE="0" VSPACE="0"></div> </NOBR></tD> <tD VALIGN=TOP ROWSPAN=2 BGCOLOR=#FFFFCC WIDTH="358"><div> In case the impedance at the feeding point of  the dipole corresponds to characteristic impedance of the cable, because the imaginary part of the antenna impedance was tuned nearly to zero, there is nearly no mismatch on the feeding cable.</div> <div> While the the imaginary part of the dipole impedance was tuned by the stub, the tuning of real part if necessary had to be done by the length of the dipole. It was intended to lower the dipoles for this purpose which luckily was not necessary.  </div> <div> The cable with the seldom characteristic impedance of 75 ohms was chosen because it was much easier to design an antenna system, in particular the shape of the dipoles,  with a dipole impedance closer to 75 ohms than to 50 ohms, the usual characteristic impedance of power cables. </div> </tD> </tR> <tR> <tD VALIGN=TOP COLSPAN=2 HEIGHT= 48 ><NOBR><div> The tubes of the stub are connected by clamps. The length of  the tubes is 5 m.</div> <bR> <div> photo: Wolfgang Heßler, T-Systems</div> </NOBR></tD> </tR> <tR> <tD VALIGN=TOP COLSPAN=2 BGCOLOR=#FFCC66 HEIGHT= 344 ><NOBR><div> <IMG SRC="71ac3520.jpg" border=0 width="451" height="338" ALIGN="BOTTOM" HSPACE="0" VSPACE="0"></div> </NOBR></tD> <tD VALIGN=TOP BGCOLOR=#FFFFCC WIDTH="358"><div> The schematic below shows how balancing, phase shifting and tuning to the output of  the transmitter (50 ohms) were realized.</div> <bR> <bR> <bR> <div> Left: centre mast near to the old transmitting building with container for antenna tuning unit. </div> <div> In front: foundation for guys of two masts</div> </tD> </tR> <tR> <tD VALIGN=TOP COLSPAN=3 BGCOLOR=#FFCC66 HEIGHT= 437 ><NOBR><div> <IMG SRC="774c1af0.gif" border=0 width="705" height="431" ALIGN="BOTTOM" HSPACE="0" VSPACE="0"></div> </NOBR></tD> </tR> <tR> <tD VALIGN=TOP COLSPAN=3 BGCOLOR=#FFFFCC HEIGHT= 118 WIDTH="822"><div> Drawing showing adaptation of dipole impdance to 50 ohms from right to left:</div> <bR> <div> - dipoles with stub (Carter loop) as balun including tuning to 75 ohms</div> <div> - feeder cables with characteristic impedance of 75 ohms</div> <div> - phaseshift of -90° without transformation</div> <div> - connection of dipoles ( theoretically 37.5 ohms )</div> <div> - transformation from 37.5 ohms to 50 ohms </div> </tD> </tR> </TABLE></div> <div> <TABLE BORDER="1" CELLPADDING="6" CELLSPACING="1" WIDTH="865" BORDERCOLORLIGHT="#FFCC66" BORDERCOLORDARK="#FFFFFF" FRAME="BOX" RULES="ALL" ALIGN="BOTTOM" HSPACE="0" VSPACE="0" BGCOLOR=#FFFFCC > <tR> <tD VALIGN=TOP BGCOLOR=#FFCC66 HEIGHT= 51 ><NOBR><div> <B>previous   next</B></div> <div> <A HREF="id335.htm" TARGET="_top" TITLE="Mainflingen MW cross dipole antenna 3E"><U><B><</B></U></A><B>       </B><A HREF="id333.htm" TARGET="_top" TITLE="Mainflingen MW cross dipole antenna 5E"><U><B>></B></U></A></div> </NOBR></tD> <tD VALIGN=TOP WIDTH="309"><div> <B>Mainflingen cross dipole</B></div> <div> <A HREF="mainflingen_mw_cross_dipole_antenna_1en.htm" TARGET="_top" TITLE="Mainflingen MW cross dipole antenna 1E"><U><B>1</B></U></A><B>  </B><A HREF="id331.htm" TARGET="_top" TITLE="Mainflingen MW cross dipole antenna 2E"><U><B>2</B></U></A><B>  </B><A HREF="id335.htm" TARGET="_top" TITLE="Mainflingen MW cross dipole antenna 3E"><U><B>3</B></U></A><B>  </B><FONT SIZE="3" COLOR="#000000" FACE="Arial" ><B>4</B></FONT><B>  </B><A HREF="id333.htm" TARGET="_top" TITLE="Mainflingen MW cross dipole antenna 5E"><U><B>5</B></U></A><B>  </B><A HREF="id334.htm" TARGET="_top" TITLE="Mainflingen MW cross dipole antenna 6E"><U><B>6</B></U></A><B>  </B><A HREF="id336.htm" TARGET="_top" TITLE="Mainflingen MW cross dipole antenna 7E"><U><B>7</B></U></A><B>  </B><A HREF="id337.htm" TARGET="_top" TITLE="Mainflingen MW cross dipole antenna 8E"><U><B>8</B></U></A></div> </tD> <tD VALIGN=TOP><NOBR><div> <A HREF="id312.htm" TARGET="_top" TITLE="Mainflingen MW Kreuzdipol 4DE"><U><IMG SRC="a94331f0.gif" 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WIDTH="74"><div> <A HREF="http://www.waniewski.de/id208.htm#all_projekts_by_list_of_frequencies" TARGET="_top" TITLE="http://www.waniewski.de/id208.htm#all_pr"><U>Projects by</U></A></div> <div> <A HREF="http://www.waniewski.de/id208.htm#all_projekts_by_list_of_frequencies" TARGET="_top" TITLE="http://www.waniewski.de/id208.htm#all_pr"><U> list of frequencies</U></A></div> </tD> <tD VALIGN=TOP BGCOLOR=#FFCC66 WIDTH="94"><div> <A HREF="#previous___next" TITLE="Mainflingen MW cross dipole antenna 4E"><U>Back to top</U></A></div> <div> <A HREF="#previous___next" TITLE="Mainflingen MW cross dipole antenna 4E"><U><IMG SRC="ee10f0c0.gif" border=0 width="15" height="12" ALIGN="BOTTOM" HSPACE="0" VSPACE="0"></U></A></div> </tD> </tR> </TABLE></div> <div> <TABLE BORDER="1" CELLPADDING="6" CELLSPACING="1" WIDTH="866" BORDERCOLORLIGHT="#FFCC66" BORDERCOLORDARK="#FFFFFF" FRAME="BOX" RULES="ALL" ALIGN="BOTTOM" HSPACE="0" VSPACE="0" BGCOLOR=#FFFFCC > <tR> <tD VALIGN=TOP COLSPAN=2 BGCOLOR=#FFCC66 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