Message-ID: <2000121018451368199@zetnet.co.uk>
Date: Sun, 10 Dec 2000 18:45:13 GMT
To: rsgb_lf_group@blacksheep.org
From: "Peter Dodd" <g3ldo@zetnet.co.uk>
Subject: LF: Insulators
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Laurie said:
> I dont know how to calculate the voltage at the end of a top loading =
> wire,but I use two ribbed ceramic insulators with a peice of terelene =
> rope (5mm) between.The rope has burnt through!!!

Ceramic insulators should not be a problem. However my Admiralty 
Handbook of Wireless Telegraphy (1925) has this to say:
"Loss by Leakage over Insulators
..........................It is, therefore, the duty of the wireless 
staff to keep these (insulators) scrupulously clean, especially after 
high speed steaming, heavy rain or bad weather, since under these 
conditions the insulators will probably be covered with a 
semi-conducting layer of 'stokers dirt' and dried salt".

I don't know about 'high speed steaming' but the lake around my shack 
is now large enough for me to sign Maritime Mobile.

I find that ribbed insulators are worse for collecting dirt, which 
gets down in between the ridges. The long PA0SE ceramic insulators 
are best although the tooth brush handles should be OK. I think that 
a method of lowering the antenna for maintenance is a necessary 
design feature, especially in coastal areas.

-- 
Regards, Peter, G3LDO

<g3ldo@zetnet.co.uk>