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<body class='hmmessage'><div dir='ltr'>I do sincerely agree<br>But with the amount of land required, plus the structure and its erection, plus the earth mat and ATU - the construction of an aerial which is anything like naturally resonant is a major project and expense.<br>Hence they are nowhere near a quarter wavelength and need added capacitance and inductance in order to achieve a reasonable match.<br>This also introduces a huge question mark over the shape of the propagation envelope and removes any hope of effective modelling.<br>So overall efficiency is about 8 to 10%<br><br><div><div style="color:rgb(34, 34, 34);font-family:arial, sans-serif;font-size:12.8000001907349px;font-style:normal;font-variant:normal;font-weight:normal;letter-spacing:normal;line-height:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;widows:1;word-spacing:0px;background-color:rgb(255, 255, 255);"><font size="3"><b>Ian Hickling</b><br></font></div><font style="color:rgb(34, 34, 34);font-family:arial,sans-serif;font-style:normal;font-variant:normal;font-weight:normal;letter-spacing:normal;line-height:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;widows:1;word-spacing:0px;background-color:rgb(255, 255, 255);font-size:12pt;" size="3"><font style="color:rgb(34, 34, 34);background-color:rgb(255, 255, 255);">Partner</font></font><br><br><a href="http://www.transplanuk.com/" target="_blank" style="color:rgb(17, 85, 204);"><img alt="" src="https://ci4.googleusercontent.com/proxy/2SkDsnIzSZgRbNnNKBSiwxiFhFQWRGV55mTjVL23fulnJpstZmYxeKrrYefY4qxiSgkMrAETld64XINLXCsujE_zI5gAsQyWeCWvHixcrNYtar3Sij4YlVBgN2NSQ-n2DsgZvrnpWZlfwCQ=s0-d-e1-ft#http://www.transplanuk.com/wp-content/uploads/2014/07/transplan_UK_weblogo_190x60.png"></a><div style="color:rgb(34, 34, 34);font-family:arial, sans-serif;font-size:12.8000001907349px;font-style:normal;font-variant:normal;font-weight:normal;letter-spacing:normal;line-height:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;widows:1;word-spacing:0px;"><i><font size="3">Office: 01635 578435 (7am-11pm UK time)</font></i></div><div style="color:rgb(34, 34, 34);font-family:arial, sans-serif;font-size:12.8000001907349px;font-style:normal;font-variant:normal;font-weight:normal;letter-spacing:normal;line-height:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;widows:1;word-spacing:0px;"><i><font size="3">Carphone: 07530 980115 (only responds when driving)</font></i></div><div style="color:rgb(34, 34, 34);font-family:arial, sans-serif;font-size:12.8000001907349px;font-style:normal;font-variant:normal;font-weight:normal;letter-spacing:normal;line-height:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;widows:1;word-spacing:0px;"><i><font size="3">6 Horn Street, Compton, NEWBURY, RG20 6QS</font></i></div></div><br><br><div>> From: tlr@gairloch.co.uk<br>> To: cma-l@mailman.commedia.org.uk<br>> Date: Mon, 14 Dec 2015 17:11:10 +0000<br>> Subject: Re: [cma-l] AM V's FM<br>> <br>> ><br>> > If you need to generate 800W of RF for an EMRP of 70W I'd say you need to<br>> > improve your antenna system efficiency :-)<br>> ><br>> <br>> As you know, easier said than done for a small station David! With a typical <br>> wavelength of 200-300 metres, an efficient omnidirectional radiator can be a <br>> mighty big thing. A traditional quarter-wave vertical mast is not something <br>> you can just pop on a roof pole like an FM dipole! Loading coils can shorten <br>> it, but nonetheless efficiency rapidly falls off as you make the antenna <br>> more compact.<br>> <br>> A more surprising figure is Ian's implied 28% electrical efficiency for the <br>> AM transmitter - Nautel's J1000 offers 60%-70% efficiency (ie ~1300W <br>> consumption for 800W modulated output). The Nautel TX costs around £10k, but <br>> it would save around £1,800 electricity a year in Ian's example, so would <br>> probably pay back the extra cost in a little over 2 years.<br>> <br>> Alex<br>> <br>> ----- Original Message ----- <br>> From: "Info" <info@transmittersrus.com><br>> To: <cma-l@commedia.org.uk><br>> Sent: Monday, December 14, 2015 4:03 PM<br>> Subject: [cma-l] AM V's FM<br>> <br>> <br>> > Ian,<br>> ><br>> > If you need to generate 800W of RF for an EMRP of 70W I'd say you need to<br>> > improve your antenna system efficiency :-)<br>> ><br>> > David<br>> > Transmitters 'R' Us<br>> ><br>> > _______________ <br>> <br>> _______________________________________________<br>> <br>> Reply - cma-l@commedia.org.uk<br>> <br>> The cma-l mailing list is a members' service provided by the Community Media Association - http://www.commedia.org.uk<br>> Twitter: http://twitter.com/community_media<br>> http://www.facebook.com/CommunityMediaAssociation<br>> Canstream Internet Radio & Video: http://www.canstream.co.uk/<br>> _______________________________________________<br>> <br>> Mailing list guidelines: http://www.commedia.org.uk/about/cma-email-lists/email-list-guidelines/<br>> _______________________________________________<br>> <br>> To unsubscribe or manage your CMA-L mailing list subscription please visit:<br>> http://mailman.commedia.org.uk/mailman/listinfo/cma-l<br></div> </div></body>
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