Re: secondary frequency problem (fwd)

["Tesla list" <tesla@xxxxxxxxxx>]

---------- Forwarded message ----------
Date: Fri, 21 Sep 2007 10:15:46 +0100
From: Chris Swinson <list@xxxxxxxxxxxxxxxxxxxxxxxxx>
To: Tesla list <tesla@xxxxxxxxxx>
Subject: Re: secondary frequency problem (fwd)

Hi Bart,

> When your measuring frequency, drive the bottom of the coil with your
> generator. Place a 5" wire in the scope probe and place it about a coils
> length from the coil in mid air. Because you don't have a topload
> installed, you may have to move it a little closer, but try to keep it
> as far from the coil as possible. The ground side of the generator
> should go to an artificial ground plane placed under the coil (I've even
> used aluminum foil up until I found something better). Connect the scope
> ground to the same place. And do it outdoors away from stuff.


Wil give it a try! Though I can't do it outdoors unfortunatly :-(

> You might need to do some research to find a generator chip for the
> frequency you want. The old ICL8038 won't do it. There might be
> something newer out there these days?


The 8038 was a great IC, hard to find now, and expensive, I did look a while 
ago, did not find anything much at all :-(

>In the end, you might find it
> easier to grab a signal generator capable of say 3MHz on eBay. That's
> probably the easiest route.

Yeah could be good to find one, though I have zero cash which is always the 
deciding factor on what can be done.




>
> Regarding the frequency; Javatc will likely pull out a 2.6MHz range
> after all is said and done. This would put the 3rd harmonic near 860kHz
> which is roughly what you thought. You should also see the 2nd lower
> harmonic at 1.2 or 1.3 MHz.
>


I get 1.8mhz though it is in the bedroom so its close to a lot of things. I 
have problems finding the other harmonics, looks around 1.5mhz. 1.8mhz is 
the only real frequency I need anyway, though could be a lot higher when 
outdoors so will have to take that into acount when designing the 
electronics.




> For measuring Q you will need to provide a low impedance source (your
> generator alone is too high). Terry Fritz designed and documented an
> excellent low-z amp for just this purpose. I built one using his circuit
> and use it for all my Q measurements. But don't cross that bridge until
> needed. When your ready for the circuit just ask and I'll dig up the
> files. The low-z amp will simply take the generator signal and convert
> it to a low impedance output. There are a few various ways to do this,
> but Terry's circuit is excellent and robust for this purpose.

Sounds interesting, though like you say, probable that do not really need to 
know the Q, its out of interest more than anything.

> Not sure what happened but I expect a browser quirk. I opened the chart
> and copied the web address then pasted into the email. I have no clue
> how the odd link came up. Here is the correct link:
>
> http://www.classictesla.com/temp/Rac_Q_Chart.gif
>

Seems at some points its almost spot on , then others its way off. My coil 
could be 50% + or - in JavaTC ?

Cheers,
Chris