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Message-ID: <260286.17766.qm@web28508.mail.ukl.yahoo.com>
Date: Sun, 3 May 2009 17:13:14 +0000 (GMT)
From: Chris Osborn <g3xiz@yahoo.co.uk>
To: LF Group <rsgb_lf_group@blacksheep.org>
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Subject: LF: Field Strength Meter - advice needed
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LF,

I've just rebuilt PA0SE's field strength meter (LF Experimenters' Handbook),
modified for use on the 500 kHz band.

I've followed the published circuit as near as possible considering availabl=
e components,
the differences being:
a) I have used a small variable capacitor instead of the published varicaps.
b) I used a JFET 2N3819 in the front end instead of dual gate mosfets.
c) Obviously I now use the MW coil of the ferrite rod instead of the publish=
ed LW coil.

I have made a decent Helmholtz coil which gives a stable magnetic field yet=20=
the=20
field strength meter's output voltage is very dependent on temperature and c=
an vary up to
30 %.

I would be most grateful for any advice on curing this problem as I've spent=
 hours trying
to correct it.

73 Chris G3XIZ


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<html><head><style type=3D"text/css"><!-- DIV {margin:0px;} --></style></hea=
d><body><div style=3D"font-family:times new roman,new york,times,serif;font-=
size:12pt"><div>LF,<br><br>I've just rebuilt PA0SE's field strength meter (L=
F Experimenters' Handbook),<br>modified for use on the 500 kHz band.<br><br>=
I've followed the published circuit as near as possible considering availabl=
e components,<br>the differences being:<br>a) I have used a small variable c=
apacitor instead of the published varicaps.<br>b) I used a JFET 2N3819 in th=
e front end instead of dual gate mosfets.<br>c) Obviously I now use the MW c=
oil of the ferrite rod instead of the published LW coil.<br><br>I have made=20=
a decent Helmholtz coil which gives a stable magnetic field yet the <br>fiel=
d strength meter's output voltage is very dependent on temperature and can v=
ary up to<br>30 %.<br><br>I would be most grateful for any advice on curing=20=
this problem as I've spent hours trying<br>to correct
 it.<br><br>73 Chris G3XIZ<br><br><br><br></div></div><br>



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