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Date: Fri, 13 Jan 2012 14:17:11 -0800 (PST)
From: Andy - KU4XR <ku4xr@yahoo.com>
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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Martin:=0A=A0=0AOld Tube type=A0A.M. radios from the 50's to the early 70's=
 will be a very good source for high value,=0Aslug tuned Inductors.. I have=
 2 coils I use to tune my 160 meter Windom for 136 KHz.. Each coil is=0Aa 2=
 section - PI wound coil, tunable by a ferrite slug.. With each section con=
nected in series; I have=0Aa total of 3.2 mH of Inductance for each coil.. =
I use an Air Variable capacitor with the Inductor to make =0Aa simple " L "=
 network to=A0peak the antenna for=A0maximum signal voltage to the radio.. =
It works well for me..=0A=A0=0AFor illustration purposes, here is a link to=
 a hand drawn diagram of my antenna:=0A=A0=0Ahttp://ku4xr.webs.com/apps/pho=
tos/photo?photoid=3D145485293=0A=A0=0A73:=0A=0AAndy - KU4XR - EM75xr - Frie=
ndsville, TN. USA=0ACoordinates: N: 35=BA 43' 54" - W: 84=BA 3' 16"=0Ahttp:=
//lwca.org/grabbers/ku4xr/=0Ahttp://www.myspace.com/beaconxr=0Ahttp://ku4xr=
.webs.com=0Ahttp://lwca.org/community/YaBB.pl=0A=0A=0A----- Original Messag=
e -----=0AFrom: Martin Evans <books@mollies.freeserve.co.uk>=0ATo: rsgb_lf_=
group@blacksheep.org=0ACc: =0ASent: Friday, January 13, 2012 4:23 PM=0ASubj=
ect: Re: LF: Tuning inductance for 137kHz receive.=0A=0AYes - I was given t=
his tip by someone else yesterday, Kevin ( my apologies to the original tip=
ster - I'm in another location now, and can't recall who it was!).=0A=0AAs =
you say, the problem is to find such a radio these days - though I'm certai=
nly going to look out for one because 0.3mH to 2.8mH is an ideal range to h=
ave.=0A=0AMartin.=A0 GW3UCJ=0A=0A=0A#######################################=
#######=0A=0A=0A> Here is one effortless method that I have used for years =
to tune a random wire for LF reception:=0A> =0A> First, find an old AM car =
radio that tunes with three ganged movable ferrite slugs and extract the tu=
ning unit.=0A> The three coils are all shielded from each other and can be =
series connected in any order and polarity to maximise the total inductance=
. One unit tested here allows continuous variation from 0.3mH to 2.8mH.=0A>=
 On occasion, I have connected a fixed inductor in series to increase the m=
aximum possible inductance.=0A> =0A> I guess the major problem is to find a=
 suitable old car radio - not variable capacitor tuned.=0A> =0A> Kevin=A0 =
=A0 ZL4MD=0A> =0A>