Re: fFINAL REPORT Cu COIL vs Al COIL (fwd)

["Tesla list" <tesla@xxxxxxxxxx>]

---------- Forwarded message ----------
Date: Tue, 9 Oct 2007 03:30:39 -0700 (PDT)
From: Yurtle Turtle <yurtle_t@xxxxxxxxx>
To: Tesla list <tesla@xxxxxxxxxx>
Subject: Re: fFINAL REPORT Cu COIL vs Al COIL (fwd)

I forgot, (and am too lazy to go searching through the
hundreds of posts on this subject) are the two coils
wound with the same diameter, wire gauge, and turns?
When you say "the coils are as close to the same as I
could wind them" are you referring to physical or DC
electrically?

thanks
Adam

--- Tesla list <tesla@xxxxxxxxxx> wrote:

> 
> ---------- Forwarded message ----------
> Date: Mon, 08 Oct 2007 17:18:01 -0700
> From: Ed Phillips <evp@xxxxxxxxxxx>
> To: tesla@xxxxxxxxxx
> Subject: fFINAL REPORT Cu COIL vs Al COIL
> 
>     Here is a final report on the experiment I ran
> to compare aluminum
> and copper conductors at RF.  The coils were as
> close to the same as I
> could wind them without going to the trouble of
> putting them on a form. 
> Just air core with masking tape to hold them in
> shape, hardly an optimum
> design but good enough for these measurements. 
> Table looks OK here and
> hope it comes through.  If not will resend IF anyone
> is interested.  I've
> had my fun so the effort is not in vain.
> 
>                             Al                      
>     Cu
>             _______________     ______________     
>    f         Q        C        Leff     Q        C  
>      Leff    Q
> (Cu/Al)
> 5000    565    103.5    9.78    655    102.2    9.91
>    1.16
> 4500    547    129       9.69    625    129      
> 9.70    1.14
> 4000    515    164       9.65    600    163      
> 9.71    1.17
> 3500    505    214       9.66    565    211      
> 9.80    1.12
> 3000    479    293.5    9.59    535    291.5    9.66
>    1.12
> 2500    438    428       9.47    495    423.5   
> 9.57    1.13
> 2400    425    463       9.50    490    460      
> 9.56    1.16
>       0      0                                0
> 
> Frequencies in kHz, capacitance in uufd         
>                                
> Data            Al           Cu                     
>  
> WIRE        0.125"    #12               
> Rdc mW    12.3        17.3               
> 
>     Bottom line is that the Q of the copper coil was
> close to 15% higher
> than that of the aluminum coil wound with a larger
> conductor.  The
> inductance of the copper coil was about 1%  higher
> so, assuming the AC
> resistance of the wire was independent of turn
> spacing, for the same
> inductance its Q would be 1% lower and the ratio of
> Q's would be about
> 14%. 
> 
>     Here's some tortured reasoning saying this
> difference is reasonable
> and about what be expected.  Per simple theory the
> ratio of the AC
> resistance of wires of the same size should vary
> inversely as the square
> root of the resistivities and should scale with wire
> size as the inverse
> of the diameter.  Based on this I think it's safe to
> say that,
> independent of wire diameter, the ratio of AC
> resistance to DC resistance
> should scale inversely as the square root of the DC
> resistance.  This is
> certainly comparable to the observed 14% and
> probably not coincidental.
> 
>     I should mention that these data were measured
> with a 50 year old [at
> least] Boonton 160A Q meter with "swap meet"
> calibration.  All of the Q's
> were high enough that I had to use the X2.5 setting
> on the drive meter
> and it was mighty difficult to make sure the
> adjustment was the same each
> time.
> 
> Ed
> 
> 
> 
> 



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