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Message-ID: <F96F56AE81AF42B3941E4F2CC814F888@JimPC>
From: "James Moritz" <james.moritz@btopenworld.com>
To: <rsgb_lf_group@blacksheep.org>
References: <29880.89039.qm@web28513.mail.ukl.yahoo.com> <AANLkTikAzPk+jo9DKHC5soq8=Khsw=xeZJL4eSgeKB3P@mail.gmail.com> <677318.41353.qm@web28511.mail.ukl.yahoo.com>
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Date: Wed, 29 Dec 2010 11:38:16 -0000
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Subject: Re: LF: VLF Loading Coil Problems - G3XIZ
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Dear Chris, LF Group,

The varnish is likely to be the culprit - for one thing, it probably has 
fairly poor AC dielectric properties, which will increase losses; for 
another, it has a higher dielectric constant than air, and filling in the 
gaps between turns with dielectric will increase distributed capacitance, 
increasing circulating currents in the coil, also increasing losses. You 
might find things improve a bit if the coil is left for a period so that any 
residual solvent in the varnish can evaporate.

Just varnishing a few narrow strips along the winding would reduce the 
losses from this source.Cable ties passed through 2 small holes drilled in 
the coil form are an effective way of anchoring the turns in place.

Cheers, Jim Moritz
73 de M0BMU