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From: John Barrett <2thman1@gmail.com>
Subject: Re: [LML] Re: Antennas for 406 MHz ELTs


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Same antenna as the 121.5 ELT. Carbon airframe IVPs generally run them horiz=
ontally in the top of the tail section (fiberglass here) - at least I did - a=
nd therefore if you are replacing the old ELT simply connect the  406 unit t=
o the old antenna. If new build, just follow suggestions of MFG to get the s=
ame result.

Correct me if I'm wrong.......l

Cheers,
John Barrett=20

Sent from my iPad


> On May 8, 2014, at 6:35 AM, Colyn Case <colyncase@earthlink.net> wrote:
>=20
> so for a carbon air frame,  seems like your options are to either put it i=
n the tail or stick it out the top of the fuselage?
>=20
> On May 7, 2014, at 6:53 AM, John Cooper wrote:
>=20
> Ron and Tom--
>=20
> But don't the "whip" antennas supplied with the 406 MHz ELTS require a gro=
und plane? The antenna that comes with the ACK E-04 is clearly dedigned for e=
xternal mounting on a metal skin. See: http://www.aircraftspruce.com/pages/a=
v/elts_zack/whipantennaE04.php   What I am looking for is either a quarter-w=
ave "rubber duck" antenna that mounts directly to the ELT, or preferably a c=
opper foil half-wave dipole that I can bond to the inner surface of my aircr=
aft.
>=20
> Being a Ham Radio operator in a former life, I know that a quarter wave wh=
ip antenna is cut for one specific frequency and performance is degraded at a=
ll other frequencies unless some kind of "trap" or impedance-matching device=
 is installed. Theoretically, a quarter-wave antenna for 406 MHz should be s=
omewhere around 7" long. For 121.5 MHz it should be around  23" long. Clearl=
y the whip antennas that come with the ELT units are cut for some intermedia=
te frequency which is a compromise that works "OK" at both 406 and 121.5.
>=20
> And what about polarization? The 121.5 and 243MHz signals should be vertic=
ally polarized like your COMM antenna(s), but technically the 406 MHz should=
 be circularly polarized which would either require a helical antenna or two=
 crossed dipoles. Of course the polarization would depend upon whether your a=
ircraft was upright or not :-(
>=20
>>=20
>> Subject: Re: [LML] Re: Antennas for 406 MHz ELTs
>> From: Ron Galbraith <cfi@instructor.net>
>> Date: 5/6/2014 7:40 AM
>> I just installed an ME406 ELT.  The antenna is around 12-14"long thin whi=
p and is for 121.5/243.0/406mhz.  Installs easily inside a glass airframe.=20=

>>=20
>> Ron
>=20
>=20

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<html><head><meta http-equiv=3D"content-type" content=3D"text/html; charset=3D=
utf-8"></head><body dir=3D"auto"><div>Same antenna as the 121.5 ELT. Carbon a=
irframe IVPs generally run them horizontally in the top of the tail section (=
fiberglass here) - at least I did - and therefore if you are replacing the o=
ld ELT simply connect the &nbsp;406 unit to the old antenna. If new build, j=
ust follow suggestions of MFG to get the same result.</div><div><br></div><d=
iv>Correct me if I'm wrong.......l</div><div><br></div><div>Cheers,</div><di=
v>John Barrett&nbsp;<br><br>Sent from my iPad<div><br></div></div><div><br>O=
n May 8, 2014, at 6:35 AM, Colyn Case &lt;<a href=3D"mailto:colyncase@earthl=
ink.net">colyncase@earthlink.net</a>&gt; wrote:<br><br></div><blockquote typ=
e=3D"cite"><div>so for a carbon air frame, &nbsp;seems like your options are=
 to either put it in the tail or stick it out the top of the fuselage?<div><=
br><div><div>On May 7, 2014, at 6:53 AM, John Cooper wrote:</div><br class=3D=
"Apple-interchange-newline">
 =20
    <meta content=3D"text/html; charset=3DISO-8859-1" http-equiv=3D"Content-=
Type">
 =20
  <div text=3D"#000000" bgcolor=3D"#FFFFFF">
    <div class=3D"moz-cite-prefix">Ron and Tom--<br>
      <br>
      But don't the "whip" antennas supplied with the 406 MHz ELTS
      require a ground plane? The antenna that comes with the ACK E-04
      is clearly dedigned for external mounting on a metal skin. See:
      <a class=3D"moz-txt-link-freetext" href=3D"http://www.aircraftspruce.c=
om/pages/av/elts_zack/whipantennaE04.php">http://www.aircraftspruce.com/page=
s/av/elts_zack/whipantennaE04.php</a>&nbsp;&nbsp;
      What I am looking for is either a quarter-wave "rubber duck"
      antenna that mounts directly to the ELT, or preferably a copper
      foil half-wave dipole that I can bond to the inner surface of my
      aircraft.<br>
      <br>
      Being a Ham Radio operator in a former life, I know that a quarter
      wave whip antenna is cut for <u>one specific frequency</u> and
      performance is degraded at all other frequencies unless some kind
      of "trap" or impedance-matching device is installed.
      Theoretically, a quarter-wave antenna for 406 MHz should be
      somewhere around 7" long. For 121.5 MHz it should be around&nbsp; 23"
      long. Clearly the whip antennas that come with the ELT units are
      cut for some intermediate frequency which is a compromise that
      works "OK" at both 406 and 121.5.<br>
      <br>
      And what about polarization? The 121.5 and 243MHz signals should
      be vertically polarized like your COMM antenna(s), but technically
      the 406 MHz should be <u>circularly </u>polarized which would
      either require a helical antenna or two crossed dipoles. Of course
      the polarization would depend upon whether your aircraft was
      upright or not :-(<br>
      <br>
    </div>
    <blockquote cite=3D"mid:listdigest-6861962@logan.com" type=3D"cite">
      <table class=3D"header-part1" width=3D"100%" border=3D"0" cellpadding=3D=
"0" cellspacing=3D"0">
        <tbody>
          <tr>
            <td>
              <div class=3D"headerdisplayname" style=3D"display:inline;">Sub=
ject:
              </div>
              Re: [LML] Re: Antennas for 406 MHz ELTs</td>
          </tr>
          <tr>
            <td>
              <div class=3D"headerdisplayname" style=3D"display:inline;">From:=

              </div>
              Ron Galbraith <a class=3D"moz-txt-link-rfc2396E" href=3D"mailt=
o:cfi@instructor.net">&lt;cfi@instructor.net&gt;</a></td>
          </tr>
          <tr>
            <td>
              <div class=3D"headerdisplayname" style=3D"display:inline;">Dat=
e:
              </div>
              5/6/2014 7:40 AM</td>
          </tr>
        </tbody>
      </table>
      <br>
      <div class=3D"moz-text-plain" wrap=3D"true" graphical-quote=3D"true" s=
tyle=3D"font-family: -moz-fixed; font-size: 14px;" lang=3D"x-western">
        <pre wrap=3D"">I just installed an ME406 ELT.  The antenna is around=
 12-14"long thin whip and is for 121.5/243.0/406mhz.  Installs easily inside=
 a glass airframe.=20

Ron</pre>
      </div>
    </blockquote>
    <br>
  </div>

</div><br></div></div></blockquote></body></html>=

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