Date: Tue, 30 Mar 2010 08:52:53 +0200
To: "rsgb_lf_group@blacksheep.org" <rsgb_lf_group@blacksheep.org>
From: Rik Strobbe <rik.strobbe@fys.kuleuven.be>
In-Reply-To: <MFEJIKCLCMPDFHOKMANAMEAFOFAA.paulc@snet.net>
References: <0F2B77385FC04A07A080811EE2E61079@JimPC>
 <MFEJIKCLCMPDFHOKMANAMEAFOFAA.paulc@snet.net>
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Message-Id: <20100330065247.BC15A31E703@smtps01.kuleuven.be>
Subject: Re: LF: RE: Re: PF per Meter  dependant on wire size?
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Hello Paul,

multiple (parallel) topload wires have been used by various stations.
Depending on the number of parallel wires and their distance values 
up to 15pF/m have been reached, 55m thus could be good  for up to 825pF.
You can find some information on my website: 
http://www.strobbe.eu/on7yd/136ant/#CapTop

73, Rik  ON7YD - OR7T

At 00:36 30/03/2010, you wrote:
>Hi Jim
>
>Thank you for the formula for calculating "C" of a wire.
>Also the information about adding additional wires is valuable.
>
>There are 2 methods I could try with my 55 meters of wire.
>With the use of fiberglass spreaders, multiple wires could be spread apart
>at the top of the tower forming a fan of the wires.
>With a single point on the shack end where the wires would all would
>combine.
>
>Probably better would be to support 4 wires equally spaced on a fiber glass
>poles 9 meters long on both the tower end and the shack end.
>
>This seems too easy Jim, there must be a point of diminishing returns.
>
>Knowing that the wire is 55 meters long, and 1 wire measures at 340 pf would
>you hazard a guess as to 4 wires 1 meter apart each the value of "C"
>
>Do you think 700 pf is achievable?
>
>Thank you for reading
>
>PaulC
>W1VLF
>
>
>
>
>-----Original Message-----
>From: owner-rsgb_lf_group@blacksheep.org
>[mailto:owner-rsgb_lf_group@blacksheep.org]On Behalf Of James Moritz
>Sent: Sunday, March 28, 2010 4:09 PM
>To: rsgb_lf_group@blacksheep.org
>Subject: LF: Re: PF per Meter dependant on wire size?
>
>
>Dear Paul, LF Group,
>
>One formula for C per unit length:
>
>C = 24/Log(4H/d) picofarads/m , H= height, m, d = diameter, m
>
>So the capacitance depends on the logarithm of the ratio of height over wire
>diameter, which only varies a little for a large change in diameter, e.g for
>1mm wire at 10m high = 5.2pF/m, 10mm diameter wire at 10m high 6.7pF/m.
>Actually this formula only applies to an infinitely long, uniform,
>horizontal, straight wire. In practice, the presence of ends, downleads,
>things on the ground, insulation on the wire, etc. etc. will all have an
>effect, and are difficult to calculate, so 6pF/m is usually as good an
>estimate as you are likely to get.
>
>Adding multiple wires will increase capacitance. If the wires are many
>metres apart (spacing large compared to height), you can multiply the
>capacitance by the number of wires. But usually, the wires are more closely
>spaced, and there is less increase in capacitance. The figures I have to
>hand are for two 1mm wires 100mm apart, C is higher by 39% compared to a
>single wire, 1m apart and C is 68% higher.
>
>Cheers, Jim Moritz
>73 de M0BMU
>
>----- Original Message -----
>From: "Paul A. Cianciolo" <paulc@snet.net>
>To: <rsgb_lf_group@blacksheep.org>
>Sent: Sunday, March 28, 2010 8:24 PM
>Subject: LF: PF per Meter dependant on wire size?
>
>
> > Hello,
> >
> > I see from previous posts that a number of  aprox 6 PF what size wire is
> > this for?
> >
> > Increasing wire size should in "C"  as should several conductors in
> > parallel
> > spaced a few feet apart.
> >
> > PauLC
> >
> > W1VLF
> >
> >
> >
> >