Message-ID: <000201c05d07$98dc42e0$7417883e@default>
From: "MAL HAMILTON" <MAL@g3kev.freeserve.co.uk>
To: "rsgb" <rsgb_lf_group@blacksheep.org>
Subject: LF: keep cool
Date: Sat, 2 Dec 2000 17:16:18 -0000
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With the advent of large LF amplifiers and proposed super large amplifiers
capable of running up to 3kw output to the antenna, there is a requirement
to keep the loading coil COOL.
Method 1
Use microbore copper tube to wind the coil. Interleave the turns with one of
the poly varities ropes to keep turns evenly spaced on coil former. If you
use ribbed former you will not need the rope. One 200 litre plastic water
tank situated near by with a central heating circulating pump feeding into
the low end of the coil tube . The top end of the coil tube is positioned
over the top of the tank to vent the hot water into it. Use plastic thermal
heating tube to connect between tank and coil at both ends.
This will keep the loading coil cool for 50% duty cycle. For very slow cw or
prolonged psk or msk use a larger tank say 600 litres or use Method 2.

Method 2

Use plastic thermal tube to connect the coil feed to your mains water supply
and vent it into a drain. The mains water pressure should be sufficient to
keep the coil cool but if not then use a high pressure pump.

Both these methods work and are required if using above 2 kw output and for
those using 3kw and up use 25 mm  copper covered thermal plastic insulated
tube for your coil.
Dont waste all those hundreds of watts heating up your coil, send it up the
antenna.

Let us all know how you get on.
73 de Mal/G3KEV