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Message-ID: <3.0.1.16.20020212152435.08e71a5a@pb623250.kuleuven.be>
Date: Tue, 12 Feb 2002 15:24:35
To: rsgb_lf_group@blacksheep.org
From: "Rik Strobbe" <rik.strobbe@fys.kuleuven.ac.be>
Subject: Re: LF: LITZ WIRE
In-reply-to: <3C691C9E.61A8BCA1@netscapeonline.co.uk>
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Hi Mal,

You are right, for the loading coil of a vertical antenna the Q is often no
so critical as ground loss etc... in most cases is much larger than the
loss in the coil.
But in respect with loop antennas the quality of the wire is much more
important as this is most likely the dominant loss factor. So if you want
to use a transmitting loop the choise of wire is very important.

73, Rik

At 13:46 12/02/02 +0000, you wrote:
>Rik gave a good description of Litz wire in a recent message and the hi
>Q qualities and theory is correct, however in practical terms it depends
>whether you really need a hi Q coil or not.
>My experience shows-
>
>1. A loading coil used to resonate a 136 khz antenna using normal 2.5 mm
>insulated wire has a lower Q than Litz but more stable and less prone to
>seasonal changes like, rain, sunshine, leaves on or off trees, wind
>blowing the antenna wires about etc ie needs no retuning once set up for
>optimum matching for a long period of time.
>
>2. A loading coil of the same inductance wound with 4mm litz wire
>behaves differently. Because of the much higher Q  the slightest breeze
>or some rain and it needs retuning to resonance, also sudden
>fluctuations are not good for the FET pa. It needs to be watched
>carefully.
>So it depends whether you want the last drop of RF and hi Q or a
>fraction less RF and less trouble.
>I cannot notice any real difference as regards radiating efficiency
>between the two coils.
>Anyone using 160 metres /M with the usual 8 ft loaded whip will have
>noticed this when passing close to other vehicles or close to trees etc
>and the higher the coil Q the worse it got.
>I am currently experimenting with a 0.4 mh litz wound coil to resonate
>my LF antenna and find it hard to keep spot on resonance with the recent
>windy conditions. I did not have any problems in similar wx conditions
>using 2.5mm insulated wire for the coil of the same inductance.
>My system is all matched to 50 ohms and the swr monitored continuously
>when transmitting so any fluctuations or changes are immediately
>noticed.
>I thing a  loop antenna wound with litz wire and exposed to the elements
>would be even harder
>to keep resonant because of the Q factor.
>It would be interesting to hear others observations about Litz v Normal
>insulated wire for outside resonating coils.
>73 de Mal/G3KEV
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