ÿþ<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"> <html> <head lang="en-GB"><title>Reception of local radio stations - Measurement test</title> <META content="The measurement test investigates how much antenna position means for reception of weak local radios. Five indoor positions are used." name="description"> <META content="local radio, weak signal, FM radio, indoor antenna, antenna position, polarization, signal strength, frequency spectrum, Copenhagen" name="keywords"></head> <body lang="en-GB" bgcolor="#ddeeee"> <table border="2" bordercolor="#c0c0ff" bgcolor="#a0a0ff" width="775" lang="en-GB" align="center"><tr> <td align="center"><img style="WIDTH: 765px; HEIGHT: 124px" src="http://www.morefmradio.dk/Logo_moreFMradio.gif" align=middle alt="logo"> <HR size="2" color="#c0c0ff"><br> <table width="740" align="center"><tr><td> <table cols="3" border="2" bordercolor="#c0c0ff" bgcolor="#ffffad" cellpadding="11" align="center"><tr> <td border="2" bordercolor="#c0c0ff" bgcolor="#d0d0ff" width="80" valign="top"><font face="arial" size="3" color="#ffffff"><br><br><br>&nbsp; &nbsp; Content <table cellpadding="3" cellspacing="5" colls="1"> <tr><td bgcolor="#66aacc"><font face="arial" size="2" color="#ffffff"><a href="http://www.morefmradio.dk/index.html">Homepage </a></font></td></tr> <tr><td bgcolor="#66aacc"><font face="arial" size="2" color="#ffffff"><a href="http://www.morefmradio.dk/Signal_strength_and_interference.html">Strength and interference</a></font></td></tr> <tr><td bgcolor="#66aacc"><font face="arial" size="2" color="#ffffff"><a href="http://www.morefmradio.dk/Antenna_type.html">Antenna <br>type</a></font></td></tr> <tr><td bgcolor="#66aacc"><font face="arial" size="2" color="#ffffff"><a href="http://www.morefmradio.dk/FM_radio_receiver.html">FM radio receiver</a></font></td></tr> <tr><td bgcolor="#66aacc"><font face="arial" size="2" color="#ffffff"><a href="http://www.morefmradio.dk/Listening_test.html">Listening <br>test</a></font></td></tr> <tr><td bgcolor="#66aacc"><font face="arial" size="2" color="#ffffff"><a href="http://www.morefmradio.dk/Measurement_test.html">Measurement test</a></font></td></tr> <tr><td bgcolor="#66aacc"><font face="arial" size="2" color="#ffffff"><a href="http://www.morefmradio.dk/Summary_of_listening_and_measurement_tests.html">Summary of tests</a></font></td></tr> <tr><td bgcolor="#66aacc"><font face="arial" size="2" color="#ffffff"><a href="http://www.morefmradio.dk/Switch_for_two_antennas.html">Antenna switch</a></font></td></tr> <tr><td bgcolor="#66aacc"><font face="arial" size="2" color="#ffffff"><a href="http://www.morefmradio.dk/Replacement_of_ceramic_filters_in_radio_receivers.html">Replacement of filters</a></font></td></tr> </table></font></td> <td border="2" bordercolor="#c0c0ff"><font face="arial" color="#0000FF" size="4">Measurement test</font><HR size="2" color="#c0c0ff"> <font face="arial" size="3"> <br> <font color="#0000FF">-- Example of the reception of local radio outside of a larger city <br> -- Measurement of antenna signal in different positions of a dipole </font> <br> A measurement test is performed with a indoor antenna in different positions to examine how much the position means for the reception of weak local radio stations outside of a larger city (in this example, 30 km west of Copenhagen). Signal strength is measured with a dipole in five different positions. <br><br> -- H1: A horizontal position with the sensitivity in E-W direction <br> -- H2: A horizontal position that is half a wavelength in front (E) of H1 <br> -- H3: A horizontal position with the sensitivity in N-S direction <br> -- V1: A vertical position <br> -- V2: A vertical position that is half a wavelength in front (east) of V1 <br><br> In comparison, the signal strength of the radio stations is also measured in the socked of a community antenna system (CA). <br><br> The result is shown in Table 2. <br><br> The sum of the measured signal strengths is shown at the bottom of the table. <br><br> <table bgcolor="#bbffbb" border="2" bordercolor="#70ee70" cols=1 align="center"><tr><td> <pre width="58"> Table 2 H1 H2 H3 V1 V2 CA MHz dB¼ dB¼ dB¼ dB¼ dB¼ dB¼ km Station ---------------------------------------------------------- 87,6 18 20 14 19 18 13 29 Radio Krishna.. 89,2 38 33 32 40 38 36 11 Radio City 90,1 12 20 13 25 22 13 29 Radio Joy.. 90,2 33 32 20 21 22 33 20 Radio Ballerup 90,4 11 32 Christiania Radio 92,9 11 14 11 15 16 28 Radio Storkbh.. 93,1 15 12 14 11 16 43 Radio Kattegat 94,5 28 22 13 17 30 29 19 Albertslund Nærra. 95,2 10 26 Hvidovre Nærradio.. 95,5 16 14 17 16 30 Universitetsradio.. 97,7 20 17 14 16 18 27 Radio Frederiksb.. 97,8 62 65 53 58 57 52 2 Roskilde Dampra.. 98,2 24 22 22 25 18 20/36 R. Køge (1)/R. 10 FM 98,9 17 12 13 18 17 31 Radio Karen.. 100,7 11 18 25 25 19 23 SLR 100,9 23 23 20 20 22 28 Radio Gladsaxe 101,2 12 17 Radio Oasen 102,9 26 26 20 15 26 18 28 Station Kbh.. 103,4 12 13 33 Station Amager 104,3 11/44 (R.100s)/R.Humleborg 104,5 19 16 13 14 38 Radio Halsnæs 104,7 18 23 30 29 29 14 22 Den Kristne R. 105,9 13 15 21 11 13 12 23 Radio Rødovre.. 106,1 25 16 30 32 32 18 25 NRJ 106,3 16 16 17 10 13 11 31 Nørrebro Radio.. 106,6 56 68 63 57 63 60 2 The Voice 106,7 43 Jet FM 106,8 20 29 27 20 25 18 17 Radio Køge (2) 107,0 18 20 13 19 27 20 39 Radio Odsherred (1) 107,7 46 67 59 47 56 54 3 Radio 100 soft 107,9 17 18 15 14 27 12 40 Radio Odsherred (2) ---------------------------------------------------------- Total 602 631 546 619 654 475 T.(-4) 400 398 339 408 440 273 </pre> </td></tr></table> <br> <font color="#0000FF"> -- Evaluation of test result</font> <br><br> The table shows that the signal strength of the antenna varies with the position of the dipole. It makes a difference if the dipole is vertically or horizontally polarized and if it is shifted or not. For example, the signal strength increases from 12 to 25 dB at 90.1 MHz, when switching from horizontal to vertical polarization. The station can be received with the vertical antenna, but not with the horizontal. In most cases, the change between the different positions is significantly less. But a proper positioning of the antenna can be crucial for the reception of a weak local radio, as every dB increases the chances for reception. However, some stations have such low signals that there is no reason to expect reception at all. <br><br> The table also shows that adjustment of the antenna is a way to reduce splatter from adjacent channels. On a vertical antenna (V1) the signal at 90.1 MHz is 4 dB higher than at 90.2 MHz. A good receiver can handle this without splatter. If a horizontal antenna (H2) is used the station at 90.1 MHz cannot be heard, as it is 12 dB below the signal on the adjacent higher channel. No receiver can handle this situation. <br><br> The bottom of the table shows the sum of the signal strengths for each antenna position. If the contribution from the four nearest transmitters is removed, the sum will be around 400. The horizontal dipole H3 with the sensitivity in the north-south direction gives a lower signal overall, since most transmitters are located in the eastern direction. <br><br> It can be seen from the figures that none of the antenna positions H1, H2, V1 and V2 in all cases are better than the others. In principle they are equally good. But one antenna position might be better to receive some stations than others. It depends on the polarization, the direction sensitivity of the antenna and the horizontal / vertical alignment. It is important to use two antennas for a stationary system, so there is the opportunity to choose one with a good signal from the desired station. Use of two antennas will ensure reception of more local radio stations in good quality as the signal increases by 3 dB or more with one third of the stations. <br><br> The "CA" column of the table shows that the community antenna system is not very useful. The sum of the signal strengths is substantially less than from the dipole in any of the positions. Only six stations can be received and that is the same as can be achieved with a simple wire antenna behind the system. <br><br> <font face="arial" size="2" color="#0000ff">Diagrams showing measured antenna signal for all transmitters in the frequency range of 87 to 108 MHz:</font> <br><br> <table cellpadding="3" cellspacing="5" colls="4" align="center"> <tr><td bgcolor="#66aacc"><font face="arial" size="2" color="#ffffff"><a href="http://www.morefmradio.dk/Signal_strength_of_dipole_87_to_90_MHz.gif">87 to 90 MHz</a></font></td> <td bgcolor="#66aacc"><font face="arial" size="2" color="#ffffff"><a href="http://www.morefmradio.dk/Signal_strength_of_dipole_90_to_93_MHz.gif">90 to 93 MHz</a></font></td><td bgcolor="#66aacc"><font face="arial" size="2" color="#ffffff"><a href="http://www.morefmradio.dk/Signal_strength_of_dipole_93_to_96_MHz.gif">93 to 96 MHz</a></font></td> <td bgcolor="#66aacc"><font face="arial" size="2" color="#ffffff"><a href="http://www.morefmradio.dk/Signal_strength_of_dipole_96_to_99_MHz.gif">96 to 99 MHz</a></font></td></tr> <tr><td bgcolor="#66aacc"><font face="arial" size="2" color="#ffffff"><a href="http://www.morefmradio.dk/Signal_strength_of_dipole_99_to_102_MHz.gif">99 to 102 MHz</a></font></td> <td bgcolor="#66aacc"><font face="arial" size="2" color="#ffffff"><a href="http://www.morefmradio.dk/Signal_strength_of_dipole_102_to_105_MHz.gif">102 to 105 MHz</a></font></td><td bgcolor="#66aacc"><font face="arial" size="2" color="#ffffff"><a href="http://www.morefmradio.dk/Signal_strength_of_dipole_105_to_108_MHz.gif">105 to 108 MHz</a></font></td></tr> </table> </font></td><td border="2" bordercolor="#c0c0ff" width="80" valign="middle" bgcolor="#d0d0ff"><font face="arial" size="3"><br><br><br><img style="width: 80px; height: 2000px" src="http://www.morefmradio.dk/Tower1.JPG" alt="telecommunication tower"></font><br><br></td></tr></table></td></tr></table><br></td></tr></table> <script language="javascript1.2" src="http://www.parameter.dk/counter/48c8b1faf410504fbe6301bc149ad788"></script> </body> </html>