Re: crystal oscillator

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

Original poster: "Terry Fritz" <twftesla-at-qwest-dot-net>

Hi Billy,

He must have had a tube type coil.  However, these are usually tuned
naturally by the circuit component values.  It would be hard to make one
crystal controlled.  My CW coil is, but that is very very rare:

http://hot-streamer-dot-com/TeslaCoils/MyCoils/CWCoil/

I guess they had TV 50 years ago ;-)  But I am not sure you would notice
interference along with all the other interference back then :-))  Today so
much is cable TV...  I assume this new "digital cable" TV is even more
immune to RFI?  I have never heard of cell phone or any modern radio stuff
being affected seriously by a Tesla coil unless it was "too close".

However, if you properly ground any Tesla coil and make good tight short
connections, the emitted RFI will not travel very far.  Fairly unlikely to
bother the neighbors (the sound may...)  We are still pondering the
wonderful spectrum graphs Finn sent, but coil RFI is rarely a real problem.

Most coils are in the 50kHz to 500kHz frequency which does not get close to
TV and radio aside from the higher frequency noise from the spark gap.
Tube coils should be much quieter in that respect.  Avoid the AM radio band
540 to 1700 kHz.  If any receiver is very close, RFI may overwhelm the
input section of the receiver and be heard but it would have to be very
close (like 20 feet).

There are some real industrial frequencies (13.56 MHz comes to "my" mind
:-)) but in the 50 - 500 kHz range we usually just hit the frequency we hit
and try no to bother anyone.  99% of the time, all is well.

There has been much discussion of all this in the past, but the "real"
problems are very few as long as your coil is grounded and the wiring is
not too horrible...  Those few that do have a problem can ask here and we
can usually get it solved.

Cheers,

	Terry


>At 08:23 PM 10/20/2001 -0700, you wrote: 
>Hello all,
>I had a quick conversation with an old timer the other day.(He built a TC 
>"maybe 50 years ago".He was pretty concerned with the coil interfering with 
>the neighbors reception etc.Anyway, he said to wind it to an industrial 
>frequency and use a crystal oscillator with a clean class AB linear power 
>amp to drive it.Could someone explain this setup to me? I think I read once 
>that the amps were inefficient for this use.
>Thanks
>Billy Mck.
>