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Date: Thu, 12 Jan 2012 12:11:51 +0000 (GMT)
From: M0FMT <m0fmt@yahoo.co.uk>
To: "rsgb_lf_group@blacksheep.org" <rsgb_lf_group@blacksheep.org>
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Subject: Re: LF: Tuning inductance for 137kHz receive.
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Hi again Martin=0A=0A=0AThe two other replies are from of the most experien=
ced 136 ops (James and Stefan)=A0and constructors around. I only play at it=
. Rather than use=A0my slide rule oops sorry a scientific calculator for ca=
lculating coils I use software down loaded from =A0http://dl5swb.de/html/mi=
ni_ring_core_calculator.htm=A0 it covers cored and aircored inductors. You =
can do a lot of "what=A0 ifs" quickly=A0I find and the measured result is p=
retty close=A0to. =0A=0AKeep at it.=0A=0A=0A73 es GL Pete M0FMT IO91UX=0A=
=0AFrom: Martin Evans <books@mollies.freeserve.co.uk>=0ATo: rsgb_lf_group@b=
lacksheep.org =0ASent: Thursday, 12 January 2012, 11:02=0ASubject: Re: LF: =
Tuning inductance for 137kHz receive.=0A=0AMorning, Pete.=0A=0AThanks for t=
his.=0A=0AYes, this is what I should do. My problem is that I get carried a=
way -=A0 I=0Abegin by thinking of making a variometer - then I decide that =
it *must* be=0Athe biggest one ever - so I search for a *huge* former - whi=
ch I can't=0Afind - and so it goes.=0A=0APathetic really.=0A=0AMaybe my res=
olution for 2012 should be to stop daydreaming and actually *do*=0Asomethin=
g!=0A=0AMartin=A0 GW3UCJ.=0A=0A########################################=0A=
=0AJust make a variometer two inductors one inside the other like piston an=
d=0Acylinder and adjust in and out to resonance (I think this design is the=
=0Asimplest form of variometer mechanically). I use a couple of plastic pai=
nt=0Abuckets, mine are 200mm diameter. 3mH looks about right for the antenn=
a=0Adescribed but fine inductance adjustment is necessary and it is best to=
 get=0Aas high a 'Q' as you can. The band is very narrow and 'Q' helps redu=
ce out=0Aof band high power signals. I am in fact describing my TX setup th=
e primary=0Ainductor is a large 600mm diameter coil tapped. All my inductor=
s are air=0Acored.=0A=0AFor RX you can tune the inductor with a large varia=
ble capacitor strapped=0Aacross because there are no flash over issues. It =
is quite simple to make=0Athese tuning coils from scratch a lot of wire tho=
ugh, but I would recommend=0Ait.=0A=0ATry Rick Strobbe ON7YD's site highly =
recommended=0Ahttp://www.strobbe.eu/on7yd/136ant/#Introduction=0A=0AHope th=
is helps.=0A=0A73 es GL Pete M0FMT IO91UX
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<html><body><div style=3D"color:#000; background-color:#fff; font-family:ta=
homa, new york, times, serif;font-size:12pt"><div style=3D"RIGHT: auto"><SP=
AN style=3D"RIGHT: auto">Hi again Martin<BR style=3D"RIGHT: auto" class=3Dy=
ui-cursor></SPAN></div>
<DIV></DIV>
<DIV style=3D"RIGHT: auto">&nbsp;</DIV>
<DIV style=3D"RIGHT: auto">The two other replies are from of the most exper=
ienced 136 ops (James and Stefan)&nbsp;and constructors around. I only play=
 at it. Rather than use&nbsp;my slide rule oops sorry a scientific calculat=
or for calculating coils I use software down loaded from &nbsp;<A style=3D"=
RIGHT: auto" href=3D"http://dl5swb.de/html/mini_ring_core_calculator.htm">h=
ttp://dl5swb.de/html/mini_ring_core_calculator.htm</A>&nbsp; it covers core=
d and aircored inductors. You can do a lot of "what&nbsp; ifs" quickly&nbsp=
;I find and the measured result is pretty close&nbsp;to. </DIV>
<DIV style=3D"RIGHT: auto">&nbsp;</DIV>
<DIV style=3D"RIGHT: auto">Keep at it.<VAR id=3Dyui-ie-cursor></VAR></DIV>
<DIV></DIV>
<div><BR><BR></div>
<DIV>73 es GL Pete M0FMT IO91UX<BR>
<DIV style=3D"FONT-FAMILY: tahoma, new york, times, serif; FONT-SIZE: 12pt"=
>
<DIV style=3D"FONT-FAMILY: times new roman, new york, times, serif; FONT-SI=
ZE: 12pt">
<DIV dir=3Dltr><FONT size=3D2 face=3DArial>
<DIV style=3D"BORDER-BOTTOM: #ccc 1px solid; BORDER-LEFT: #ccc 1px solid; P=
ADDING-BOTTOM: 0px; LINE-HEIGHT: 0; MARGIN: 5px 0px; PADDING-LEFT: 0px; PAD=
DING-RIGHT: 0px; HEIGHT: 0px; FONT-SIZE: 0px; BORDER-TOP: #ccc 1px solid; B=
ORDER-RIGHT: #ccc 1px solid; PADDING-TOP: 0px" class=3Dhr readonly=3D"true"=
 contenteditable=3D"false"></DIV><B><SPAN style=3D"FONT-WEIGHT: bold">From:=
</SPAN></B> Martin Evans &lt;books@mollies.freeserve.co.uk&gt;<BR><B><SPAN =
style=3D"FONT-WEIGHT: bold">To:</SPAN></B> rsgb_lf_group@blacksheep.org <BR=
><B><SPAN style=3D"FONT-WEIGHT: bold">Sent:</SPAN></B> Thursday, 12 January=
 2012, 11:02<BR><B><SPAN style=3D"FONT-WEIGHT: bold">Subject:</SPAN></B> Re=
: LF: Tuning inductance for 137kHz receive.<BR></FONT></DIV><BR>Morning, Pe=
te.<BR><BR>Thanks for this.<BR><BR>Yes, this is what I should do. My proble=
m is that I get carried away -&nbsp; I<BR>begin by thinking of making a var=
iometer - then I decide that it *must* be<BR>the biggest one ever - so I se=
arch for
 a *huge* former - which I can't<BR>find - and so it goes.<BR><BR>Pathetic =
really.<BR><BR>Maybe my resolution for 2012 should be to stop daydreaming a=
nd actually *do*<BR>something!<BR><BR>Martin&nbsp; GW3UCJ.<BR><BR>#########=
###############################<BR><BR>Just make a variometer two inductors=
 one inside the other like piston and<BR>cylinder and adjust in and out to =
resonance (I think this design is the<BR>simplest form of variometer mechan=
ically). I use a couple of plastic paint<BR>buckets, mine are 200mm diamete=
r. 3mH looks about right for the antenna<BR>described but fine inductance a=
djustment is necessary and it is best to get<BR>as high a 'Q' as you can. T=
he band is very narrow and 'Q' helps reduce out<BR>of band high power signa=
ls. I am in fact describing my TX setup the primary<BR>inductor is a large =
600mm diameter coil tapped. All my inductors are air<BR>cored.<BR><BR>For R=
X you can tune the inductor with a large variable capacitor
 strapped<BR>across because there are no flash over issues. It is quite sim=
ple to make<BR>these tuning coils from scratch a lot of wire though, but I =
would recommend<BR>it.<BR><BR>Try Rick Strobbe ON7YD's site highly recommen=
ded<BR><A href=3D"http://www.strobbe.eu/on7yd/136ant/#Introduction" target=
=3D_blank>http://www.strobbe.eu/on7yd/136ant/#Introduction</A><BR><BR>Hope =
this helps.<BR><BR>73 es GL Pete M0FMT IO91UX<BR><BR><BR><BR><BR></DIV></DI=
V></DIV></div></body></html>
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