RE: RF Ground Connections - Wire Type

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Malcolm Watts by way of Terry Fritz <twftesla-at-qwest-dot-net>" <m.j.watts-at-massey.ac.nz>

Hi Dan,

> Original poster: "Mccauley, Daniel H by way of Terry Fritz
<twftesla-at-qwest-dot-net>" <daniel.h.mccauley-at-lmco-dot-com>
> 
> 
> 	I'm going to have to disagree with your assessment.  For high
> voltage transients, stranded or braided wire outperforms solid wire in all
> instances.  This is the primary reason you use braided wire for lightning
> protection in house security systems etc...  Another example is the use of
> stranded wire vs. solid in audio applications.  
> 
> 	Dan

A few years ago I did a set of measurements using a variety of 
conductors as 17' leads from the base of a secondary coil to a ground 
path and the findings agreed with Gary's. Braid in particular was a 
terrible performer and to prove the point, I included a foot of it in 
TC primary to check the temperature rise which was substantial. I 
would be interested to see some measurements which show otherwise.

     I would not expect the differences to be notable at audio 
frequencies where skin depths are comparable with overall conductor 
diameter. Stranded wire is most often used where mechanical 
flexibility is required.

Regards,
malcolm
 
> 
> 
> > My recent measurements of conductor AC resistance confirm that stranded
> > wire is a POOR choice.  While one should strive for a high surface area,
> > this only applies to solid conductors.  RF currents want to travel only on
> > the outermost surface - they will not travel on strands inside the bundle.
> > When a strand goes from the surface of the bundle to inside the bundle,
> > the
> > current will try to hop to an outer strand, through whatever surface
> > oxides
> > might be in its path.  I did not compare finely stranded conductors with
> > coarsely stranded conductors, but I would speculate that a coarsely
> > stranded conductor might have a lower AC resistance, as it's a closer
> > approximation to a solid conductor.
> > 
> > Steel cable, solid or otherwise, would be a very poor conductor due to the
> > inherently higher resistance of steel compared to copper.
> > 
> > Since heavy gauge solid wire is inflexible and not practical for a cable,
> > I
> > would recommend a copper ribbon for the best possible conductor.  Home
> > Depot sells copper roof flashing by the foot, you would have to cut it
> > into
> > strips and solder them together.
> > 
> > Now to the practical aspects.  An RF ground, good or bad, will have
> > virtually no effect on the coil's performance.  Several list members have
> > accidentally forgotten to connect their secondary base to a ground of any
> > sort, and there was NO impact on performance!  The real reason for using a
> > ground has more to do with preventing RF interference and HV RF nasties
> > from entering your house wiring.
> > 
> > Gary Lau
> > MA, USA
> > .  
> > 
> >  -----Original Message-----
> > From: 	Tesla list [mailto:tesla-at-pupman-dot-com] 
> > Sent:	Tuesday, July 16, 2002 10:09 AM
> > To:	tesla-at-pupman-dot-com
> > Subject:	RF Ground Connections - Wire Type
> > 
> > Original poster: "Mccauley, Daniel H by way of Terry Fritz
> > <twftesla-at-qwest-dot-net>" <daniel.h.mccauley-at-lmco-dot-com>
> > 
> > 
> > 
> > 	Do you think steel braided cable (kind used in ground discharge
> > sticks, winches, etc...) would be a good connection.  Theres a lot of
> > surface area there, its cheap, but not sure on the material.
> > 
> > 	Thanks
> > 	Dan
> > 
> > 
> > 
> > 
> > 
> > > Use a proper copper ground rod available at almost any electric supply
> > > shop
> > > or hardware store.
> > > 
> > > Do not use a galvanized pipe.  Use copper.  You want the best possible
> > > ground you can get.  Also for lead wire use 2 to 4 gauge fine stranded
> > > welding cable.
msnip...