ÿþ<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"> <html> <head lang="en-GB"><title>Reception of local radio stations - Signal strength and interference</title> <META content="Reception of local radio outside the coverage area is possible when the antenna signal is at least 15 dB¼." name="description"> <META content="local radio, signal strength, chances of reception, antenna signal, interference, splatter, ceramic filter, tuning, antenna position" 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">Signal strength and interference</font><HR size="2" color="#c0c0ff"> <font face="arial" size="3"> <br> <font color="#0000FF"> -- Signal strength at the reception locality</font> <br><br> The signal strength at the reception locality depends, inter alia, on transmitter power and height of transmitting antenna. The listener has no influence on these conditions. It also depends on distance to transmitter. A local radio transmitter can almost always be received at a distance of up to 10 km using a good receiving system. If the distance to the transmitter is between 10 and 20 km, the chances of receiving the station decline, but they are still good. If the distance is between 20 and 30 km less than half the radios can be received. The chances become small when there are more than 30 km to the transmitter. <br><br> Signal strength also depends on the place where the receiving antenna is located. An external antenna on a mast usually gives a higher antenna signal than an indoor antenna. The latter may, in turn, provide a good signal if the house is in an open area and the walls of the house allow passage of FM radio waves (brick and wood walls). In that case an indoor antenna may be as good as an external antenna. <br><br> Reception of local radio outside the coverage area is possible when the antenna signal is at least 15-20 dB¼ measured on a dipole. If the signal is weaker the chances of reception, even with particular good system, are very low. If the signal is above 30-35 dB¼ any receiving system can be used. <br><br> <a href="http://www.morefmradio.dk/Signal_strength_vs._distance_to_transmitter_color.gif"> <img src="http://www.morefmradio.dk/Signal_strength_vs._distance_to_transmitter_color.gif" align="middle" alt="Signal strength vs. distance to transmitter"></a> <br> These pages relate to the situation where the signal is in the range between the two limits. The diagram shows that the signal from many local radio transmitters is within the range providing the opportunity to receive more FM radio stations. <br><br> <font color="#0000FF"> -- Interference from other FM transmitters</font> <br><br> Interference from other transmitters has also influence on the reception of weak local radios. There may be another local radio on the same frequency with a stronger signal than the station to be received. The only remedy in this situation is to try different antenna positions. <br><br> A more frequent source of interference is the so-called splatter, which is due to transmitters on neighboring channels that swing into the frequency band being received. The problem can be reduced by using a quality receiver with ceramic filters. The splatter problem can also be reduced by tuning a little bit away from the interfering transmitter so that the signal is weakened. Some modern receivers may by themselves tune to the best result or they may have a signal processing that reduces splatter. Finally, a change of the antenna position may help giving the antenna a better position where the desired signal is strong and the undesirable signal weak. A shift of the antenna or a change of its polarization can often provide improvements. <br><br> <a href="http://www.morefmradio.dk/Spectrum_93_MHz.JPG"> <img src="http://www.morefmradio.dk/Spectrum_93_MHz.JPG" align="right" hspace="10" alt="Spectrum of FM radio transmitters at 93 MHz. Horizontal div.=0.2 MHz. Vertical div.=10 dB"> </a> <br><br><br><font size="2" color="#0000FF">Spectrum showing local FM transmitters at 92.8, 92.9, 93.0 and 93.1 MHz.<br>Center frequency=93.0 MHz; horizontal div.=0.2 MHz; vertical div.=10 dB</font> <br><br> <br><br></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: 1400px" src="http://www.morefmradio.dk/Tower.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>