Re: PC board primaries

["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 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 
> 
> 
> 
>