RE: Al duct vs Chicken Wire

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: "Qndre Qndre" <qndre_encrypt@xxxxxxxxxxx>

Hey Gary,

I do not fully agree with you. The topload is part of the resonant 
circuit so you will have to take some things into account. It's not 
that a bigger capacitance will give better results. It has advantages 
to use bigger toploads as well as it has advantages to use smaller toploads.

1. Since the output voltage is equal to the breakdown voltage of the 
spark gap (which is usually close to the output voltage of the power 
supply) multiplied by the ratio of primary capacitor to secondary 
capacitor smaller toploads will give you higher output voltages.

2. Since the topload is the capacitor in the resonant circuit 
together with the secondary coil you will get higher frequencies by 
using one with a lower capacitance as well. Higher frequencies AND 
higher voltages seem to be twice a good deal so using a rather small 
topload seems to me like a good way of doing it.

3. There is however one drawback: You do reduce your output current 
this way (since I = P / U) so your streamers won't get that hot and 
bright any more. However, if you have decided on how much voltage and 
how much current you want to get out of your secondary and into the 
air you can calculate the right topload capacitance to use.

4. If you have to use a given secondary inductance you can also 
calculate the topload capacitance required for the output frequency 
you want to have (the desired frequency will probably be around 200 kiloHertz).

5. If you have a too big topload, you may get no streamers into the 
air at all since the voltage is too low to make the large curvature break down.

So let's summarise things a bit...


Small Topload cap:

+ Higher output voltage
+ Higher resonant frequency
+ Lower breakdown voltage
+ High streamer count
+ Relatively quiet operation
- Lower output current
- Cooler streamers
- Streamers don't have much brightness


Large Topload cap:

+ Higher output current
+ Hotter streamers
+ Brighter streamers
- Lower output voltage
- Lower resonant frequency
- Higher breakdown voltage
- Low streamer count
- Ear-defeaning operation


Regards, Q.

----Original Message Follows----
From: "Tesla list" <tesla@xxxxxxxxxx>
To: tesla@xxxxxxxxxx
Subject: RE: Al duct vs Chicken Wire
Date: Mon, 09 Jan 2006 19:14:59 -0700


Original poster: "Lau, Gary" <Gary.Lau@xxxxxx>

It is true that to achieve a single long streamer one must minimize
surface irregularities, but even more important, the toroid must be the
correct size.  And the only way to know what size that is is to make an
educated guess, based on the experience of others, build it, and see how
it performs.  If it's smooth and you still get multiple streamers, you
need a bigger top load.  Luckily one can stack multiple toroids.

Regards, Gary Lau
MA, USA

> Original poster: Just Justin <rocketfuel@xxxxxxxxxxxxx>
>
> I'll probably build a chicken wire toroid anyway,
> but I wanted to ask for opinions on the performance
> of a chicken wire-based topload vs Aluminum ducting.
>
> I currently have a 4" inner diameter Al duct as my
> topload and I get about streamers breaking out of
> about 5-6 places simultaneously.  Is is true that
> with a perfectly smooth toroid there tends to be
> one large streamer instead of many smaller ones?
>
> Thanks!
>
> Justin in Austin
>