[TowerTalk] Cable on a reel using a formula?

[Matt Patterson]

Isn't the formula pi * radius(squared) * the number of turns what you need?

Been a long time since I did any geometry...


Matt




----- Original Message ----- 
From: "Pat Barthelow" <aa6eg at hotmail.com>
To: <dolanmorrison at tiscali.co.uk>; <towertalk at contesting.com>
Sent: Thursday, October 06, 2005 12:22 PM
Subject: Re: [TowerTalk] Cable on a reel using a formula?


>
>>How
>>to calculate the amount of cable on a reel using a formula?
>>Anybody know this formula.
>>GM0LZE
>
> I used to have an Allied Electronics reference guide from the 60s
> That had a formula for big audio inductors where the bobbin
> dimensions(diameter and spool length)
> the wire diameter were entered and it could calculate inductance,
> resistance....
>
> Hmmm...mebbe a better way...er two better ways...if the cable is newly
> manufactured, it often
> has foot or metre markers with  numbers marked on the jacket every
> foot..look at both ends and subtract...but that  would be too easy.. so
> probably not an option in your case...
> If Coax, and very long, take a good hi res ohmmeter, short one end, and
> measure the
> loop resistance and look up the factory loop resistance figures for that
> kind of cable..so
>
> Maybe some old solenoid design engineering formulas can be had to do the
> trick....
>
> Or, Get an MFJ 259B, and connectorize the free spool end, and use the 
> legth
> function of the 259B to calculate the length to the end...
>
> 73, DX Pat AA6EG  aa6eg at hotmail.com
>
>
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