AW: [TCML] Toroid Problems / Tank wiring

["Fritz W. Egli" <fritz@xxxxxxxxxxxxxx>]

Dear All,
To the thema tank wiring I respectfully report the following fact:
Small coil, 6/30 powered, produced after carefull tuning 36 to 37cm sparks.
Following the advice of a experianced coiler I relocated tank components for
shortest possible wiring and used for wiring insted of previous 1mm
conductor diam. wires, 3mm cond. diam. wires. All connections bolted, ring
connectors. Nothing else changed exept slightly prim. tap point readjusted.
Result: sparks 39 to 40cm. Happy smile. So I believe the advice given to
Nicholas is of good basic value, even if there is no obvious, direct
arithmetic proove??
Mit freundlichen Grüssen, Fritz

A few arithmetic errors, corrected below..
jimlux wrote:
> Quarkster wrote:
>> Nicholas -
>>
>> A few areas of concern are revealed by your photos:
>>
>> 1. It looks like your tank wiring to the MMC and spark gap is
>> extremely small gage stranded wire (#16 AWG?). All the interconnects
>> between primary coil, spark gap, and tank capacitor need to be fairly
>> heavy gage (I recommend no smaller than #12 AWG for a small NST
>> powered coil). The peak current in the tank circuit can be hundreds
>> of amps when the spark gap fires and the tank capacitor dumps all of
>> its energy, and #16 AWG is not adequate.
>
> This is just not true.  The peak current may be relatively high, but
> even so, the losses just aren't that high, compared to the losses in the
> gap itself.  Consider that the difference in diameter between AWG 12 and
> 16 is about a factor of 1.4.  Therefore, the loss goes as the same ratio.
>

This assumes that for RF, the AC resistance runs roughly as the
circumference of the conductor. For DC, where the entire cross sectional
area is used, the resistance ratio will be more like 2:1.. (a bit more..
3 gauges is twice/half the resistance)


> Let's assume for a moment that you have AWG 10 wire (just because it's
> easy to remember the resistance.. 1 mOhm/ft).. Say you have 2 feet..
> that's 2 mOhm total.  Also assume that the peak current is 1000 Amps (
> if Cpri is 0.1 uF and Lpri is 30 uH, 15kV turns into 866A, assuming NO
> losses anywhere else)
>
> So the voltage drop across that couple feet of wire is 2V.. compare that
> to the 100V or so across the gap.
>
> Now, go to AWG 16, which will have twice the resistance (at DC).. Now
> the drop in the wire is 4V.. Overall the loss has increased by 2/104, or
> about 2%...

Here, I used the DC resistance, which is inconsistent with my assertion
above that one should use the AC resistance, which in turn is
proportional to circumference.  So, AWG16 is 1/4 the circumference of
AWG10.. so 8V drip vs 2V, for a 4% total loss.



Sorry, all..
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