Re: PC board primaries

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

Original poster: "R Heidlebaugh by way of Terry Fritz <twftesla-at-qwest-dot-net>" <rheidlebaugh-at-zialink-dot-com>

on 12/11/01 5:37 PM, Tesla list at tesla-at-pupman-dot-com wrote:

> Original poster: "Malcolm Watts by way of Terry Fritz <twftesla-at-qwest-dot-net>"
> <m.j.watts-at-massey.ac.nz>
> 
> Hi Robert,
> I see where you are coming from now. I too have used
> striplines and agree about the characteristics of PCB tracks. Have
> you any quantitative data to show that such a coil causes any more
> radiated wideband hash than an air insulated spiral of roughly the
> same dimensions when used as part of a TC? As we all know, TCs are
> notorious emitters of high frequencies mainly due to step functions
> associated with the primary gap and output discharges and parasitic
> radiators coupled to these components by varying degrees.
> The matter of capacitance between tracks place atop one another
> on opposite sides of the board may or may not much difference to the
> fundamental primary frequency depending on the size of the coil wrt
> the value of primary capacitance.
> 
> Regards,
> malcolm
> 
> On 10 Dec 2001, at 21:41, Tesla list wrote:
> 
>> Original poster: "R Heidlebaugh by way of Terry Fritz
> <twftesla-at-qwest-dot-net>" <rheidlebaugh-at-zialink-dot-com>
>> A circuit board acts as a strip-line circuit which can and will produce
>> harmonics easly over 2 GHz. Low value ceramic or mica capacitors at the
>> terminal points of the copper runs will prevent self oscilation of the runs.
>> High value resistors will also reduce the circuit Q and stop oscilation. A
>> wire coil has a large wind to wind capacitance that dampens oscilations
>> along the turn to turn length of the winding preventing standing wave high
>> frequency oscilations. A circuit board has nearly no winding to winding
>> capacitance, but has high inductance and no resistance to dampin the Q along
>> the runs so standing wave oscilations pop up along the runs. THE LACK OF
>> turn to turn capacitance makes the resinant frequency of the natural coil
>> high. When a two sided board coil is used just the opposite happens. The
>> capacitance through the board is very high, much higher than air between
>> coil windings of an ordinary coil so the natural double coil frequency is
>> much lower than a free air coil. The results is much lower external
>> capacitance is neaded.I hope this helps. I have used PC board coils and
>> strip line resonant circuits. The trial and error time is fun, but quite
>> rewarding when you are done. I use copper tape to make my lay-out board and
>> do my testing before I etch my final board. This saves a lot of trial and
>> error cost. Copper tape is available at glass shops and larger hobby shops
>> that cater to stained glass hobbyists.
>> Robert  H 
>> 
>> 
>> 
>> 
> 
> 
> 
> 
I have a slight problem with hard data. My house/library was burned dowm by
a badge waring gurglar. In general, at any sharp bend or corner a standing
wave will tend to form.The frequency will tend to be 85% of  the free air
wave length of the run. Propigation is slower on a PC run. Any sudden
current change produces standing wave harmonics. The nature of the TC is to
use sudden high current (spark gap) pulses to produce high voltage pulses in
the output. This is a natutal place for TVI. Rounded corners reduce
problems, but dont stop all problems
   Robert   H