ÿþ<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"> <html> <head lang="en-GB"><title>Reception of local radio stations - Replacement of ceramic filters</title> <META content="Replacement of ceramic filters can reduce splatter in an FM radio. Filters having a bandwidth of 150 kHz are used." name="description"> <META content="local radio, FM radio, selectivity, bandwidth, splatter, interference, ceramic filter, Murata, Sony M600, IC socket" 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">Replacement of ceramic filters in radio receivers</font><HR size="2" color="#c0c0ff"><font face="arial" size="3"> <br> The frequency spacing between strong FM transmitters is usually so large that the transmitters do not interfere with each other. The matter is different when it comes to weak radio transmitters such as local radio transmitters in a larger city. The frequency spacing is smaller and the number of transmitters is higher. In areas outside the city reception can be difficult due to interference. The selectivity of even modern radio receivers is insufficient. The receivers are designed with a view to produce hi-fi stereo and to receive RDS. Thus, the filters are broader than necessary to produce audio. <br><br> It is a good idea to test different receivers to find the best for reception of weak radio transmitters. A few receivers can be switched to a narrow IF-bandwidth so that splatter is reduced. <br><br> If the test is unsuccessful a replacement of the receiver s filters with narrower filters can be considered. The loss of quality using narrow filters need not be audible for a general listening. However, the replacement requires some expertise in electronics. <br><br> <a href="http://www.morefmradio.dk/Ceramic_filter.JPG"> <img style="WIDTH: 75px; HEIGHT: 94px" src="http://www.morefmradio.dk/Ceramic_filter.JPG" align="right" hspace="10" alt="Murata ceramic filter, center frequency 10,700 kHz"></a> For experimental purpose, I have replaced the two ceramic filters in a Sony M600 with Murata ceramic filters having a bandwidth of 150 kHz. <br><br> First, I remove the filters of the receiver by rocking them gently back and forth until they get loose. Now the filters can no longer be used. <br><br> <a href="http://www.morefmradio.dk/Ceramic_filters_in_sockets.JPG"> <img style="WIDTH: 125px; HEIGHT: 125px" src="http://www.morefmradio.dk/Ceramic_filters_in_sockets.JPG" align="right" hspace="10" alt="Ceramic filters in sockets"></a> The debris of the filter pins is removed from the PCB, and a severed part of an IC socket with three holes is soldered to the PCB where the filter was before. The new filter is placed in the holes of the IC socket part with the text side facing the same way as before. Now the radio can be closed and used with  better filters. <br><br> Removal of the filters can be made more elegantly by using the method that is described here: <br><a href="http://pages.cthome.net/fmdx/filter.htm">http://pages.cthome.net/fmdx/filter.htm</a> <br><br> The filters of the receiver must have a center frequency of 10,700 kHz (red dot). Site about ceramic filters: <a href="http://www.geocities.com/rbrucecarter/ceramic_filter.htm">http://www.geocities.com/rbrucecarter/ceramic_filter.htm</a> <br><br> Ceramic filters can be purchased from Digi-Key: <a href="http://digikey.com">http://digikey.com</a> <br><br> After the modification the radio reception is somewhat better with the improved selectivity. It is more pleasant to listen to the broadcasts, because the splatter is reduced. In addition, some new radio stations can be received with noise. <br><br> Site about better FM reception: <a href="http://home.computer.net/~pritch/betterfm.htm">http://home.computer.net/~pritch/betterfm.htm</a> <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: 900px" 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>