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<DIV><FONT size=2>The top horizontal section is an active part of the
deisgn as well as being a support for the main vertical radiator Ian. It
essential forms one plate of a capacitor with ground.</FONT></DIV>
<DIV><FONT size=2></FONT> </DIV>
<DIV><FONT size=2>It's a traditional (since before radio broadcasting
began) design of shortened LF antenna. As I have always understood it, it's
is essentially a vertical radiator, with a horizontal ladder across the top
forming capacitive loading that allows the vertical radiator to be more
efficient than it otherwise would be without being a full quarter-wave high. The
radiation pattern is pretty much omnidirectional, regardles of the azimuth of
the horizontal section over the top.</FONT></DIV>
<DIV><FONT size=2></FONT> </DIV>
<DIV><FONT size=2>They are a good solution if you happen to have a pair of
reasonably tall structures between which the horizontal section can be strung,
such as Capital Radio's Lotts Road power station chimneys, or the Titanic's
funnels.</FONT></DIV>
<DIV><FONT size=2></FONT> </DIV>
<DIV><IMG border=0 hspace=0 alt="" align=baseline
src="cid:5D83F5A8BC2F45ECA043A5BBEA13CE5C@wwpc04"></DIV>
<DIV><FONT size=2></FONT> </DIV>
<DIV><FONT size=2>Alex</FONT></DIV>
<BLOCKQUOTE
style="BORDER-LEFT: #000000 2px solid; PADDING-LEFT: 5px; PADDING-RIGHT: 0px; MARGIN-LEFT: 5px; MARGIN-RIGHT: 0px">
<DIV style="FONT: 10pt arial">----- Original Message ----- </DIV>
<DIV
style="FONT: 10pt arial; BACKGROUND: #e4e4e4; font-color: black"><B>From:</B>
<A title=transplanfm@hotmail.com href="mailto:transplanfm@hotmail.com">Ian
Hickling</A> </DIV>
<DIV style="FONT: 10pt arial"><B>To:</B> <A
title=cma-l@mailman.commedia.org.uk
href="mailto:cma-l@mailman.commedia.org.uk">The Community Media Association
Discussion List</A> </DIV>
<DIV style="FONT: 10pt arial"><B>Sent:</B> Saturday, December 19, 2015 10:10
AM</DIV>
<DIV style="FONT: 10pt arial"><B>Subject:</B> [cma-l] AM v FM</DIV>
<DIV><BR></DIV>
<DIV dir=ltr>By a "T-Antenna" are we referring here to a vertical radiator
acting as something approaching a bottom-fed quarter wave radiator held in
place by a horizontal "dead" wire on either side - or a horizontal dipole fed
by a vertical wire or line - or a combination of these?<BR>It's important - as
propagation will be different in each case.<BR>The antenna we will be using
for this project (dictated by land and funding available) will be a simple 6m
vertical pole using insulating stays, a capacitance hat and a loading coil in
the ATU at the base.<BR>Efficiency will be about 8% - hence 1kW port output to
give 70W EMRP.<BR><BR>
<DIV>
<DIV
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size=3><B>Ian Hickling</B><BR></FONT></DIV><FONT
style="WIDOWS: 1; TEXT-TRANSFORM: none; BACKGROUND-COLOR: rgb(255,255,255); TEXT-INDENT: 0px; FONT: 12pt arial,sans-serif; WHITE-SPACE: normal; LETTER-SPACING: normal; COLOR: rgb(34,34,34); WORD-SPACING: 0px"
size=3><FONT
style="BACKGROUND-COLOR: rgb(255,255,255); COLOR: rgb(34,34,34)">Partner</FONT></FONT><BR><BR><A
style="COLOR: rgb(17,85,204)" href="http://www.transplanuk.com/"
target=_blank><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
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size=3>Office: 01635 578435 (7am-11pm UK time)</FONT></I></DIV>
<DIV
style="WIDOWS: 1; TEXT-TRANSFORM: none; TEXT-INDENT: 0px; FONT: 12px arial, sans-serif; WHITE-SPACE: normal; LETTER-SPACING: normal; COLOR: rgb(34,34,34); WORD-SPACING: 0px"><I><FONT
size=3>Carphone: 07530 980115 (only responds when driving)</FONT></I></DIV>
<DIV
style="WIDOWS: 1; TEXT-TRANSFORM: none; TEXT-INDENT: 0px; FONT: 12px arial, sans-serif; WHITE-SPACE: normal; LETTER-SPACING: normal; COLOR: rgb(34,34,34); WORD-SPACING: 0px"><I><FONT
size=3>6 Horn Street, Compton, NEWBURY, RG20
6QS</FONT></I></DIV></DIV><BR><BR>
<DIV>
<HR id=stopSpelling>
Date: Tue, 15 Dec 2015 22:26:56 +0000<BR>From: tlr@gairloch.co.uk<BR>To:
cma-l@mailman.commedia.org.uk<BR>Subject: Re: [cma-l] AM V's FM<BR><BR>Sure
David, that's been a standard design for LF and MF antennas for over a
century. It is a vertical radiator with a capacitive top load to allow it to
be shorter, but it still depends on significant height to be efficient, and is
still a very big unwieldy structure compared to a half-wave VHF dipole stuck
up on a pole! <BR>As you say, the T ideally needs wetlands and in any event a
good earth system below. As I recall, when Capital Radio started up in London
they strung one between the chimneys of Lotts Road power station, and had the
advantage of being on the bank of the Thames for their earth. Most town centre
community stations won't have such a situation to hand! <BR><BR>I think the
same sort of antenna design would have been on the Titanic - now that did have
a good earth plane below it!<BR>Alex<BR><BR>
<BLOCKQUOTE>On 15 December 2015 at 14:55 Info
<info@transmittersrus.com> wrote:<BR><BR>
<DIV class=ecxox-a98c59f3ca-WordSection1>
<P style="BACKGROUND: white" class=ecxox-a98c59f3ca-MsoNormal>Ian, Alex,</P>
<P style="BACKGROUND: white" class=ecxox-a98c59f3ca-MsoNormal> </P>
<P style="BACKGROUND: white" class=ecxox-a98c59f3ca-MsoNormal>Look into the
T-antenna.</P>
<P style="BACKGROUND: white" class=ecxox-a98c59f3ca-MsoNormal> </P>
<P style="BACKGROUND: white" class=ecxox-a98c59f3ca-MsoNormal>They are
relatively low profile, do not requires huge swathes of the greenbelt and
are economically priced if you go DIY.</P>
<P style="BACKGROUND: white" class=ecxox-a98c59f3ca-MsoNormal> </P>
<P style="BACKGROUND: white" class=ecxox-a98c59f3ca-MsoNormal>Peter
‘Chicago’ Murtha installed one just outside Walthamstow for the N. London
bible basher. One can see it a couple of minutes up the road from the dog
stadium.</P>
<P style="BACKGROUND: white" class=ecxox-a98c59f3ca-MsoNormal> </P>
<P style="BACKGROUND: white" class=ecxox-a98c59f3ca-MsoNormal>SMC among
others supply the hardware.</P>
<P style="BACKGROUND: white" class=ecxox-a98c59f3ca-MsoNormal> </P>
<P style="BACKGROUND: white" class=ecxox-a98c59f3ca-MsoNormal>Pitch it up
over some wetlands with a good ground system, buried or elevated and I
reiterate, you do not require anything like 800W of RF to meet that EMRP
quota.</P>
<P style="BACKGROUND: white" class=ecxox-a98c59f3ca-MsoNormal> </P>
<P style="BACKGROUND: white" class=ecxox-a98c59f3ca-MsoNormal>BTW, make sure
you have designed an efficient antenna tuning unit which can maximize the
bandwidth so you don’t sound like you have a pillow over the mic.</P>
<P style="BACKGROUND: white" class=ecxox-a98c59f3ca-MsoNormal> </P>
<P style="BACKGROUND: white" class=ecxox-a98c59f3ca-MsoNormal>David</P>
<P
class=ecxox-a98c59f3ca-MsoNormal> </P></DIV></BLOCKQUOTE><BR>_______________________________________________
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