ÿþ<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"> <html> <head lang="en-GB"><title>Reception of local radio stations - Antenna type</title> <META content="A stationary system uses an external antenna on mast or internal room antennas. A portable radio uses a telescopic antenna." name="description"> <META content="local radio, reception, external antenna, indoor antenna, wire dipole, telescopic antenna, polarization, antenna adjustment" 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">Antenna type</font><HR size="2" color="#c0c0ff"> <font face="arial" size="3"> <br> <font color="#0000FF"> -- Introduction</font> <br><br> The choice of antenna for reception of weak local radio stations depends on the radio receiver: 1) Stationary systems can use an external antenna on a mast or an internal room antenna that may be fixed on a wall. 2) Portable radios normally use the telescopic antenna on the receiver. The choice is therefore more or less taken in advance, as type of receiver is often determined by the listener s demands for audio quality, mobility, etc. Fortunately, both types of receivers are equally good to receive weak local radios, if an indoor antenna can be used. <br><br> Different receivers and antennas are examined on the pages: listening test and measurement test. It is shown that weak local radio stations can be received equally well on a stationary radio with two indoor dipole antennas with horizontal and vertical polarization and on a portable radio with a telescopic antenna. The two systems can receive the same number of local radios, but there is a small difference in which stations they can receive. It is also shown that a stationary radio with a single indoor dipole antenna receives fewer stations than a stationary radio using two dipoles. <br><br> <font color="#0000FF"> -- External antenna</font> <br><br> An external antenna can usually be placed free of obstacles, but is not necessarily the best solution to receive weak local radios. A ring- or halo-dipole to be fitted on a mast has the advantage that it can receive transmitters around the horizon, but it has a negative gain of -6 dB. It is less suitable for the reception of weak FM transmitters. On the other hand, a Yagi-antenna with three elements has a gain of 5-6 dB in the head direction of reception, but is less good to receive transmitters from other directions. A half wave dipole receives the signals equally well from all directions, except from the longitudinal direction of the dipole. All three antenna types are usually mounted with horizontal polarization, so they have difficulty in receiving stations that transmit with vertical polarization. <br><br> An antenna mounted high on a mast can give a stronger signal than an antenna in a lower position, but the effect of a high position need not be worth the effort of raising a mast. The difference between an internal and an external antenna may be marginal in single-family houses and other houses in open areas. <br><br> An external antenna on mast is not a universal remedy to improve the reception of weak local radios, but may be the only solution in situations where the signal can not reach an internal antenna because of wall construction, low location, etc. <br><br> <font color="#0000FF"> -- Internal room antenna</font> <br><br> An internal antenna in the form of a 1.5 m dipole of wire or band cable can be a good solution to the reception of local radios, if there are no <a href="http://www.morefmradio.dk/Wire_dipole.JPG"> <img src="http://www.morefmradio.dk/Wire_dipole" align="right" vspace="10" alt="Wire_dipole"></a> obstacles that may <br>attenuate the radio signal. <br>This may, for example, be examined using a portable radio. If the reception of a weak radio station is almost the same inside and outside the house, an indoor antenna may well be used. <br><br> An antenna in the form of a wire or band cable dipole has the advantage that it is easy to test in different positions of reception. It is important that the antenna is placed where the signal is strongest for the desired local radio stations. The antenna can be positioned vertically or horizontally, depending on the polarization of the transmitter. <br><br> <a href="http://www.morefmradio.dk/Band_cable_dipole.JPG"> <img src="http://www.morefmradio.dk/Band_cable_dipole.JPG" align="right" vspace="10" alt="Band_cable_dipole"></a> The best antenna position for a certain transmitter is found by moving the antenna to one side or the other as well as upwards or downwards. The best position for one transmitter is not necessarily the best position for another transmitter. The choice of antenna position is often a compromise that takes into account how well the various stations are received and how easy it is to mount the antenna close to the receiver. <br><br> If the local radio transmitters are using varying polarizations, it is an advantage to mount two dipole antennas: a vertical and a horizontal. In this way, a better audio quality can be obtained in switching to the antenna with the strongest signal or the least disturbed reception. <br><br> <font color="#0000FF"> -- Telescopic antenna</font> <br><br> A telescopic (quarter wave) antenna on a portable radio provides a little less signal than a (half wave) dipole antenna. On the other hand, the antenna can by hand be rotated / tilted to different, suitable positions, and also the receiver can be moved to bring about the best position of reception. This gives a very flexible adjustment. Unfortunately, the audio quality of portable radio receivers is lower than the quality of stationary receivers. The quality may still be quite acceptable for less demanding tasks. <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: 1650px" 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>