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Message-ID: <1314715132.88047.YahooMailNeo@web111917.mail.gq1.yahoo.com>
Date: Tue, 30 Aug 2011 07:38:52 -0700 (PDT)
From: Daniele Tincani <danieletincani@yahoo.com>
To: "rsgb_lf_group@blacksheep.org" <rsgb_lf_group@blacksheep.org>
In-Reply-To: <4E5CF192.3040905@legal-medicine.de>
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Subject: Re: LF: Re: Ferrite wideband antennas?
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=A0=0AHello Peter,=0A=A0=0Avery helpful information! Thanks a lot.=0A=A0=0A=
BTW, I downloaded the Pelgrum's work days ago. I will read it carefully bef=
ore starting my loop construction.=0A=A0=0ABest regards=0ADaniele=0A=A0=0A=
=0AFrom: pws <pws@legal-medicine.de>=0ATo: rsgb_lf_group@blacksheep.org=0AS=
ent: Tuesday, August 30, 2011 4:20 PM=0ASubject: Re: LF: Re: Ferrite wideba=
nd antennas?=0A=0AHi Daniele,=0A=0AYou wrote:=0A> ...=0A> Yesterday evening=
 a purchased a bunch of 7 x MU400HH ferrites (10mm x 200mm each) on eBay, p=
lanning to join them together "in parallel" to form a fatter rod, no idea i=
f it will be a good choice but let's play with this new toy ;-) Meanwhile I=
'm collecting ideas and hints from the web about construction (shielding, c=
omputing/measuring parameters, ect.). Projects are stacking as usual :-)=0A=
> ...=0A=0AThese rods are working fine even at VLF. But according to my own=
 experiences in the late 90th bundling is not worth the effort. Two tight (=
!) stacked 15cm rods achieved better SNR compared to a bundle of 7 rods.=0A=
=0APELGRUM (2006) confirms these findings:=0A"...=0AThe rod-length has a la=
rger influence on the noise-performance than the rod diameter. Therefore, i=
n weight-limited applications, rod length is preferred over rod diameter. H=
owever, this may conflict with the requirements of volume-limited applicati=
ons, such as mobile/handheld.=0A..."=0Aand:=0A"...=0AIn applications where =
the antenna size is limited, it can be beneficial to use multiple small fer=
rite rods instead of a single larger rod...=0A...it can be concluded that t=
wo 10 cm rods experience virtually no mutual=0Acoupling when placed 10 cm a=
part, and therefore, result in a 3 dB increase in SNR compared to a single =
10 cm rod.=0A..."=0A=0AAnd for the coil length:=0A"...=0Athe best noise per=
formance is achieved for a fully wound rod: an=0Aimprovement in SNR of appr=
oximately 2.2 dB is obtained when a fully wound rod is used instead of a na=
rrow coil at the center of the rod.=0A..."=0A=0ASource: Wouter J. Pelgrum, =
"New Potential of Low-Frequency Radionavigation in the 21st Century", Delft=
, November 2006=0A=0AThese are empirically obtained findings!=0A=0AAccordin=
g to that and what I know from professionals (submarine) stacking works fin=
e up to length/diameter ratios of approx. 60. Above that ratio bundling may=
 be an option. Of course the challenge is to fix those stacked rods in plac=
e tightly...=0A=0APeter, df3lp
--0-985689999-1314715132=:88047
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<html><body><div style=3D"color:#000; background-color:#fff; font-family:ar=
ial, helvetica, sans-serif;font-size:10pt"><div style=3D"RIGHT: auto"><SPAN=
 style=3D"RIGHT: auto"></SPAN>&nbsp;</div>
<div style=3D"RIGHT: auto"><SPAN style=3D"RIGHT: auto">Hello Peter,</SPAN><=
/div>
<div style=3D"RIGHT: auto"><SPAN style=3D"RIGHT: auto"></SPAN>&nbsp;</div>
<div style=3D"RIGHT: auto"><SPAN style=3D"RIGHT: auto">very helpful informa=
tion! Thanks a lot.</SPAN></div>
<div style=3D"RIGHT: auto"><SPAN style=3D"RIGHT: auto"><VAR id=3Dyui-ie-cur=
sor></VAR></SPAN>&nbsp;</div>
<div style=3D"RIGHT: auto"><SPAN style=3D"RIGHT: auto">BTW, I downloaded th=
e Pelgrum's work days ago. I will read it carefully before starting my loop=
 construction.</SPAN></div>
<div style=3D"RIGHT: auto"><SPAN style=3D"RIGHT: auto"></SPAN>&nbsp;</div>
<div style=3D"RIGHT: auto"><SPAN style=3D"RIGHT: auto">Best regards</SPAN><=
/div>
<div style=3D"RIGHT: auto"><SPAN style=3D"RIGHT: auto">Daniele</SPAN></div>
<div style=3D"RIGHT: auto"><SPAN style=3D"RIGHT: auto"></SPAN>&nbsp;</div>
<div style=3D"RIGHT: auto"><BR style=3D"RIGHT: auto"></div>
<DIV style=3D"FONT-SIZE: 10pt; FONT-FAMILY: arial, helvetica, sans-serif">
<DIV style=3D"FONT-SIZE: 12pt; FONT-FAMILY: times new roman, new york, time=
s, serif"><FONT face=3DArial size=3D2>
<DIV class=3Dhr style=3D"BORDER-RIGHT: #ccc 1px solid; PADDING-RIGHT: 0px; =
BORDER-TOP: #ccc 1px solid; PADDING-LEFT: 0px; FONT-SIZE: 0px; PADDING-BOTT=
OM: 0px; MARGIN: 5px 0px; BORDER-LEFT: #ccc 1px solid; LINE-HEIGHT: 0; PADD=
ING-TOP: 0px; BORDER-BOTTOM: #ccc 1px solid; HEIGHT: 0px" readonly=3D"true"=
 contenteditable=3D"false"></DIV><B><SPAN style=3D"FONT-WEIGHT: bold">From:=
</SPAN></B> pws &lt;pws@legal-medicine.de&gt;<BR><B><SPAN style=3D"FONT-WEI=
GHT: bold">To:</SPAN></B> rsgb_lf_group@blacksheep.org<BR><B><SPAN style=3D=
"FONT-WEIGHT: bold">Sent:</SPAN></B> Tuesday, August 30, 2011 4:20 PM<BR><B=
><SPAN style=3D"FONT-WEIGHT: bold">Subject:</SPAN></B> Re: LF: Re: Ferrite =
wideband antennas?<BR></FONT><BR>Hi Daniele,<BR><BR>You wrote:<BR>&gt; ...<=
BR>&gt; Yesterday evening a purchased a bunch of 7 x MU400HH ferrites (10mm=
 x 200mm each) on eBay, planning to join them together "in parallel" to for=
m a fatter rod, no idea if it will be a good choice but let's play with thi=
s new toy
 ;-) Meanwhile I'm collecting ideas and hints from the web about constructi=
on (shielding, computing/measuring parameters, ect.). Projects are stacking=
 as usual :-)<BR>&gt; ...<BR><BR>These rods are working fine even at VLF. B=
ut according to my own experiences in the late 90th bundling is not worth t=
he effort. Two tight (!) stacked 15cm rods achieved better SNR compared to =
a bundle of 7 rods.<BR><BR>PELGRUM (2006) confirms these findings:<BR>"...<=
BR>The rod-length has a larger influence on the noise-performance than the =
rod diameter. Therefore, in weight-limited applications, rod length is pref=
erred over rod diameter. However, this may conflict with the requirements o=
f volume-limited applications, such as mobile/handheld.<BR>..."<BR>and:<BR>=
"...<BR>In applications where the antenna size is limited, it can be benefi=
cial to use multiple small ferrite rods instead of a single larger rod...<B=
R>...it can be concluded that two 10 cm rods experience virtually no
 mutual<BR>coupling when placed 10 cm apart, and therefore, result in a 3 d=
B increase in SNR compared to a single 10 cm rod.<BR>..."<BR><BR>And for th=
e coil length:<BR>"...<BR>the best noise performance is achieved for a full=
y wound rod: an<BR>improvement in SNR of approximately 2.2 dB is obtained w=
hen a fully wound rod is used instead of a narrow coil at the center of the=
 rod.<BR>..."<BR><BR>Source: Wouter J. Pelgrum, "New Potential of Low-Frequ=
ency Radionavigation in the 21st Century", Delft, November 2006<BR><BR>Thes=
e are empirically obtained findings!<BR><BR>According to that and what I kn=
ow from professionals (submarine) stacking works fine up to length/diameter=
 ratios of approx. 60. Above that ratio bundling may be an option. Of cours=
e the challenge is to fix those stacked rods in place tightly...<BR><BR>Pet=
er, df3lp<BR><BR><BR><BR></DIV></DIV></div></body></html>
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