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<p><em>Por João Roberto S. Gândara Ferreira, PY2JF.</em></p>
<div align="center">
<p style="TEXT-ALIGN:center">Tabela de R.O.E x Potência Transmitida (4W)</p>
<p style="TEXT-ALIGN:center">( <a href="http://www.cram.org.br/wordpress/?p=6197">http://www.cram.org.br/wordpress/?p=6197</a> )</p>
<p style="TEXT-ALIGN:center">
<table border="1" cellpadding="0" width="292">
<tbody>
<tr>
<td valign="bottom" width="60">
<p align="center"><b>R.O.E.</b></p></td>
<td valign="bottom" width="77">
<p align="center"><b>% de perda</b></p></td>
<td valign="bottom" width="64">
<p align="center"><b>ERP*</b></p></td>
<td valign="bottom" width="81">
<p align="center"><b>Watts transmitidos</b></p></td></tr>
<tr>
<td valign="bottom" width="60">
<p align="center">1.0:1</p></td>
<td valign="bottom" width="77">
<p align="center">0.0%</p></td>
<td valign="bottom" width="64">
<p align="center">100.0%</p></td>
<td valign="bottom" width="81">
<p align="center">4.00</p></td></tr>
<tr>
<td valign="bottom" width="60">
<p align="center">1.1:1</p></td>
<td valign="bottom" width="77">
<p align="center">0.2%</p></td>
<td valign="bottom" width="64">
<p align="center">99.8%</p></td>
<td valign="bottom" width="81">
<p align="center">3.99</p></td></tr>
<tr>
<td valign="bottom" width="60">
<p align="center">1.2:1</p></td>
<td valign="bottom" width="77">
<p align="center">0.8%</p></td>
<td valign="bottom" width="64">
<p align="center">99.2%</p></td>
<td valign="bottom" width="81">
<p align="center">3.97</p></td></tr>
<tr>
<td valign="bottom" width="60">
<p align="center">1.3:1</p></td>
<td valign="bottom" width="77">
<p align="center">1.7%</p></td>
<td valign="bottom" width="64">
<p align="center">98.3%</p></td>
<td valign="bottom" width="81">
<p align="center">3.93</p></td></tr>
<tr>
<td valign="bottom" width="60">
<p align="center">1.4:1</p></td>
<td valign="bottom" width="77">
<p align="center">2.8%</p></td>
<td valign="bottom" width="64">
<p align="center">97.2%</p></td>
<td valign="bottom" width="81">
<p align="center">3.89</p></td></tr>
<tr>
<td valign="bottom" width="60">
<p align="center">1.5:1</p></td>
<td valign="bottom" width="77">
<p align="center">4.0%</p></td>
<td valign="bottom" width="64">
<p align="center">96.0%</p></td>
<td valign="bottom" width="81">
<p align="center">3.84</p></td></tr>
<tr>
<td valign="bottom" width="60">
<p align="center">1.6:1</p></td>
<td valign="bottom" width="77">
<p align="center">5.3%</p></td>
<td valign="bottom" width="64">
<p align="center">94.7%</p></td>
<td valign="bottom" width="81">
<p align="center">3.79</p></td></tr>
<tr>
<td valign="bottom" width="60">
<p align="center">1.7:1</p></td>
<td valign="bottom" width="77">
<p align="center">6.7%</p></td>
<td valign="bottom" width="64">
<p align="center">93.3%</p></td>
<td valign="bottom" width="81">
<p align="center">3.73</p></td></tr>
<tr>
<td valign="bottom" width="60">
<p align="center">1.8:1</p></td>
<td valign="bottom" width="77">
<p align="center">8.2%</p></td>
<td valign="bottom" width="64">
<p align="center">91.8%</p></td>
<td valign="bottom" width="81">
<p align="center">3.67</p></td></tr>
<tr>
<td valign="bottom" width="60">
<p align="center">2.0:1</p></td>
<td valign="bottom" width="77">
<p align="center">11.1%</p></td>
<td valign="bottom" width="64">
<p align="center">88.9%</p></td>
<td valign="bottom" width="81">
<p align="center">3.56</p></td></tr>
<tr>
<td valign="bottom" width="60">
<p align="center">2.2:1</p></td>
<td valign="bottom" width="77">
<p align="center">14.1%</p></td>
<td valign="bottom" width="64">
<p align="center">85.9%</p></td>
<td valign="bottom" width="81">
<p align="center">3.44</p></td></tr>
<tr>
<td valign="bottom" width="60">
<p align="center">2.4:1</p></td>
<td valign="bottom" width="77">
<p align="center">17.0%</p></td>
<td valign="bottom" width="64">
<p align="center">83.0%</p></td>
<td valign="bottom" width="81">
<p align="center">3.32</p></td></tr>
<tr>
<td valign="bottom" width="60">
<p align="center">2.6:1</p></td>
<td valign="bottom" width="77">
<p align="center">19.8%</p></td>
<td valign="bottom" width="64">
<p align="center">80.2%</p></td>
<td valign="bottom" width="81">
<p align="center">3.21</p></td></tr>
<tr>
<td valign="bottom" width="60">
<p align="center">3.0:1</p></td>
<td valign="bottom" width="77">
<p align="center">25.0%</p></td>
<td valign="bottom" width="64">
<p align="center">75.0%</p></td>
<td valign="bottom" width="81">
<p align="center">3.00</p></td></tr>
<tr>
<td valign="bottom" width="60">
<p align="center">4.0:1</p></td>
<td valign="bottom" width="77">
<p align="center">36.0%</p></td>
<td valign="bottom" width="64">
<p align="center">64.0%</p></td>
<td valign="bottom" width="81">
<p align="center">2.56</p></td></tr>
<tr>
<td valign="bottom" width="60">
<p align="center">5.0:1</p></td>
<td valign="bottom" width="77">
<p align="center">44.4%</p></td>
<td valign="bottom" width="64">
<p align="center">55.6%</p></td>
<td valign="bottom" width="81">
<p align="center">2.22</p></td></tr>
<tr>
<td valign="bottom" width="60">
<p align="center">6.0:1</p></td>
<td valign="bottom" width="77">
<p align="center">51.0%</p></td>
<td valign="bottom" width="64">
<p align="center">49.0%</p></td>
<td valign="bottom" width="81">
<p align="center">1.96</p></td></tr>
<tr>
<td valign="bottom" width="60">
<p align="center">7.0:1</p></td>
<td valign="bottom" width="77">
<p align="center">56.3%</p></td>
<td valign="bottom" width="64">
<p align="center">43.8%</p></td>
<td valign="bottom" width="81">
<p align="center">1.75</p></td></tr>
<tr>
<td valign="bottom" width="60">
<p align="center">8.0:1</p></td>
<td valign="bottom" width="77">
<p align="center">60.5%</p></td>
<td valign="bottom" width="64">
<p align="center">39.5%</p></td>
<td valign="bottom" width="81">
<p align="center">1.58</p></td></tr>
<tr>
<td valign="bottom" width="60">
<p align="center">9.0:1</p></td>
<td valign="bottom" width="77">
<p align="center">64.0%</p></td>
<td valign="bottom" width="64">
<p align="center">36.0%</p></td>
<td valign="bottom" width="81">
<p align="center">1.44</p></td></tr>
<tr>
<td valign="bottom" width="60">
<p align="center">10.0:1</p></td>
<td valign="bottom" width="77">
<p align="center">66.9%</p></td>
<td valign="bottom" width="64">
<p align="center">33.1%</p></td>
<td valign="bottom" width="81">
<p align="center">1.32</p></td></tr></tbody></table></p></div>
<p style="TEXT-ALIGN:justify">A R.O.E. é uma relação, portanto deve ser sempre apresentada como tal. Não é correto dizermos que uma antena está com R.O.E. de zero ou 1.5, e sim que ela está com R.O.E. de 1:1.0 ou 1:1.5.</p>

<p style="TEXT-ALIGN:justify">Vale lembrar também que é característica intrínsica de algumas antenas uma R.O.E. diferente de 1:1.0. Muitos projetos de antenas tem como sua melhor R.O.E. em torno de 1:1.5.</p>
<p style="TEXT-ALIGN:justify">Transceptores atuais contam com um circuito de proteção que detecta quando há R.O.E. excessiva, diminuindo automaticamente sua potência para evitar danos em seus módulos ou transistores de saída.</p>

<p style="TEXT-ALIGN:justify">Para finalizar, qual seria o limite máximo seguro de R.O.E. para se transmitir? Difícil dizer. Se o rádio tem proteção, não precisamos nos preocupar, ele cuida disso. Agora se não tem, acredito que não exceder 1:2.0 é uma prática segura. Agora não é porque seu rádio tem proteção que vai transmitir de qualquer jeito. Lembre-se, com R.O.E. alta, sua potência será reduzida e o pouco que sobrar perderá boa parte em calor.</p>
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