RE: AW: [TCML] COUNTERPOISE

["Lau, Gary" <Gary.Lau@xxxxxx>]

Hi Matt,

Is it certain that eddy current losses would result if a solid counterpoise is used, or is it merely adequate to use spokes rather than a solid sheet?  I ask because I once did an experiment to gauge eddy current losses by measuring the ringdown time of an uncoupled primary coil (no secondary present).  The presence of a big NST more than about a foot below the primary had a negligible impact, so the magnetic field diminishes very quickly with distance.  I didn't try a large sheet so it may indeed have a loss, don't know for sure.

Regards, Gary Lau
MA, USA

> -----Original Message-----
> From: tesla-bounces@xxxxxxxxxx [mailto:tesla-bounces@xxxxxxxxxx] On
> Behalf Of Mddeming@xxxxxxx
> Sent: Wednesday, July 23, 2008 7:08 PM
> To: tesla@xxxxxxxxxx
> Subject: Re: AW: [TCML] COUNTERPOISE
>
> Hi Fritz,
>
> I've only built one, so I can't tell you the optimal number of wires. I  used
> 12 bare copper wires across the diameter, tied and soldered in the middle
> with another loop of wire for the secondary connection, and spread at 15 degree
> intervals. One could use 18 wires at 10 degrees. I don't know if you should
> go  with less than 12 wires (24 spokes) because it should "look" dense to the
> RF.
>
> Matt D.
>
>
> In a message dated 7/23/2008 5:41:20 P.M. Eastern Daylight Time,
> fritz@xxxxxxxxxxxxxx writes:
>
> Thank  you very much Gary, Matt, All,
>
> The "Wheel spoke" layout of the  counterpoise (radially layed out wires on
> the floor) is interesting, I  "feel" this must be the most efficient, short
> path directly back to the  base center of the coil, for all them electrons
> that shot out from the  toroid to the surounding ...?!
>
> However, I wounder, why the "Backflow"  throu a foil (or a sheetmetal?)
> counterpoise is less  efficient?
>
> "Wheel spoke" layout, how many "spokes" are succested to  your experiance? 4?
> 8? 10? more?
>
> Thank you again for your estimated  information, Fritz
>
>
> Re: [TCML] COUNTERPOISE
>
> Abends  Fritz,
>
> I only see a few possible problems with a   long cable to ground:
>
> 1. A long cable will tend to induce RF currents  into any wire it  passes
> parallel to.
> 2. A long cable might act as  a "bias resistor" to keep the base of the coil
>
> at several thousand  volts above ground potential. This is especially bad if
>
> you have one  side of the primary connected to the base of the secondary.  If
> the
> primary is "floating" then it is not so bad.
> 3. Streamers will  tend to "target" this cable for ground strikes.
> 4. With a well-designed  counterpoise, it isn't necessary.
>
> In terms of eddy currents, the least  efficient counterpoise is a foil disk,
>
> next best is a wire mesh disk,  and best is a large number of wires  laid out
>
> in a "wagon-wheel"  pattern with the coil at the hub.
>
> Matt D.
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