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Braided or Smooth Strap?

Quoting Doug:

> I'm nearing the completion of constructing my first coil 
> system, and have been assuming that I could use a large 
> diameter hose clamp (metal) to secure the ground strap braid to
> the base of the secondary coil's tube.  

Quoting Malcolm:

 > , throw the braid away and use pipe, copper strap, v. thick    
 > wire, *anything but*.

Quoting Robert W. Stephens <rwstephens-at-ptbo.igs-dot-net>:

> Wassamatta you don't like braid?  I'm starting to use it a lot
> now that I have some in stock.  Picked up a beautiful roll of 
> 1.5 inch wide, tinned copper braid at the last hamfest.  I like
> it partly because you can squish it into a large crimp 
> connector at the end (I always solder after crimping as a 
> matter of good practice). Are you poo-pooing it because of 
> something you have been told, or do you have actual pulse 
> propogation test results in a research paper. If the latter
> is true I'd love to get a copy of it.

No, I agree with Malcolm on this, and we have both measured this
effect: Braided strap has a markedly higher RF impedance than
smooth strap (like strips of metal flashing). As Malcolm states, 
even a length of #14 solid copper wire has better RF qualities
than a 1/2" wide braid strap. 

I have seen a braided groundstrap raise the dip of a coil on the
scope, a measurable decrease in coil Q that can easily be
reversed by swapping over to a smooth groundstrap.

I still use braided groundstrap, because like you, I found a deal
and stocked up (before I discovered how lousy it is for Tesla
coiling); but I only use it on the 60 cycle side of my RF ground
(pathing the transformer cores, cases, safety gap, etc., to the
RF ground). The coil and all of the strike shielding is pathed
with wide, smooth, flat, and cheap AL flashing to the RF ground.

**********IMPORTED**POST*****************************************

>From MALCOLM-at-directorate.wnp.ac.nzThu Nov 14 21:55:51 1996
Date: Fri, 15 Nov 1996 08:30:11 +1200
From: Malcolm Watts <MALCOLM-at-directorate.wnp.ac.nz>
To: tesla-at-pupman-dot-com
Subject: myfiles

Hello all,
           My post on the braid was questioned (and reasonably so). 
Here is a post I sent to the list late last year that might help
explain my stance on this one.


 ------- Forwarded Message Follows -------

PERFORMANCE OF WIRE
     The following is a summary of a brief investigation into wire
performance at low radio frequencies.
     Six wires of various types were tested. Copper strap was not
<SNIP>
solid section wires performed well in small diameters. Departure from
this was noted as significant for a thickness of 0.063mm (c.f. skin depth
of 0.15mm at the test frequency).
    Personally, I'll never use braid again in an RF application!! Imagine
how a few feet of this detracts from primary performance if it is included
within the tank circuit.

**********END**OF**IMPORTED**POST***************************************


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