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*To*: tesla@xxxxxxxxxx*Subject*: RE: twin coil transmission lines (fwd)*From*: "Tesla list" <tesla@xxxxxxxxxx>*Date*: Thu, 31 May 2007 08:20:38 -0600 (MDT)*Delivered-to*: testla@xxxxxxxxxx*Delivered-to*: tesla@xxxxxxxxxxxxxxxx*Old-return-path*: <mod1@xxxxxxxxxx>*Resent-date*: Thu, 31 May 2007 08:20:38 -0600 (MDT)*Resent-from*: tesla@xxxxxxxxxx*Resent-message-id*: <ldiR56G6gWI.A.vRE.2mtXGB@chip1>*Resent-sender*: tesla-request@xxxxxxxxxx

Original poster: List moderator <mod1@xxxxxxxxxx> ---------- Forwarded message ---------- Date: Wed, 30 May 2007 21:06:13 -0700 From: Jim Lux <jimlux@xxxxxxxxxxxxx> To: Tesla list <tesla@xxxxxxxxxx> Subject: RE: twin coil transmission lines (fwd) At 03:38 PM 5/30/2007, you wrote: >Original poster: List moderator <mod1@xxxxxxxxxx> > > > >---------- Forwarded message ---------- >Date: Wed, 30 May 2007 17:44:13 -0400 >From: "Lau, Gary" <Gary.Lau@xxxxxx> >To: Tesla list <tesla@xxxxxxxxxx> >Subject: RE: twin coil transmission lines (fwd) > >Hi Jim: > >Is it really correct to compare the skin-effect resistive losses of the >transmission line, to the primary reactance, to reach an incremental >loss percentage? The primary reactance isn't a loss at all. No, but I was attempting to find if the loss in the transmission line is a significant fraction of the overall impedance.. For example in a classic LC tuned circuit, if the Q is 100, you lose 1% of the energy in every cycle, and the X/R ratio is 100. I think other losses in the system will dominate.. the 50-100 ft of tubing in the primary, for instance, or, more likely the gap. >In contrast, the AC resistance of various primary coils that I tested >(http://www.laushaus.com/tesla/primary_resistance.htm) were 0.18 to 0.39 >Ohms for a 67uH primary at 100KHz. So if the transmission line really >did add 2 Ohms, I believe that would be significant. My calculation of AC resistance must be way off, then.. Your measurement of the 1/4" tubing coil (4" id, 10.5" od 13 turns should be about 7.75*2*pi*13 52.7 ft... 16 meters.. I would assume that if you had 5 meters of transmission line 2.5 out and 2.5 back, and it was 1/4" tubing, the Rac would be a third what you measured (0.21/3 or 0.07 ohms). I must have massively miscalculated... it's probably something like 0.02 ohms instead of 2 ohms (since my tube is 3 times the size of yours) Probably a centimeter/meter thing. Makes the transmission line and primary R losses even less of an issue.... I think gap losses are your big loss (and, of course, coupling to the secondary and power dissipated in the sparks)... A couple hundred volts drop across the gap wouldn't surprise me, and the rms gap current is probably in the tens of amps during the bang. >Regards, Gary Lau >MA, USA > > > > Date: Wed, 30 May 2007 14:16:00 -0700 > > From: Jim Lux <jimlux@xxxxxxxxxxxxx> > > To: Tesla list <tesla@xxxxxxxxxx> > > Subject: Re: twin coil transmission lines (fwd) > > > > ADate: Wed, 30 May 2007 14:54:42 +0000 > > >From: David Rieben <drieben@xxxxxxxxxxx> > > >To: tesla@xxxxxxxxxx > > >Cc: drieben@xxxxxxxxxxx > > >Subject: twin coil transmission lines > > > > > >Hi all, > > > > > >I have a question regarding the transmission lines between large > > >twin coil systems that's been bugging me for a while now. I have > > >never seriously considered building a large twin coil or magnifier > > >system, mainly due to the large space that one of these systems > > >eats up when assembled. However, I know that there's also > > >considerable line losses in the transmission lines that carry the RF > > >currents from the SG and capacitor to the primary coil(s) and that's > > >the reason that we usually try to keep the tank circuit wiring > > >between the SG/capacitor to the primary coil as short as possible > > >in a basic 2-coil SG system. > > > > Maybe the losses aren't all that huge, in comparison to other > > losses... Let's gedanken this a bit... > > > > Say you're running at 100kHz, and you're using 2cm diameter copper > > tubing as your conductor. Skin depth is 200 microns or there abouts, > > and the tube is "large" compared to the skin depth, so we can treat > > it as a sheet 6.28 cm wide and 200 microns thick, 0.126 square cm > > cross sectional area. > > > > Let's further assume you've got 5 meters of line (2.5 out and 2.5 > > back). So, the resistance is > > 1.673 micro ohm cm * 500 cm/0.126 cm^2 = about 2 ohms... > > > > Is 2 ohms important, loss wise? > > > > Using CV^2 = LI^2 and some plausible numbers, I get a few hundred > > amps as the peak current. > > > > Perhaps a better way to look at it is to compare the 2 ohms to the > > reactance of the primary at the resonant frequency = L*2*pi*f = 104 >ohms... > > > > This implies a loss of a few percent. > > > > > > > > > >

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