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Re: CW coil top terminals?



Original poster: "Jim Lux by way of Terry Fritz <twftesla-at-uswest-dot-net>" <jimlux-at-earthlink-dot-net>



Tesla list wrote:
> 
> Original poster: "David Trimmell by way of Terry Fritz
<twftesla-at-uswest-dot-net>" <davidt-at-pond-dot-net>
> 
> Hello Dunckx,
> 
> Actually I was serious, as Audio Modulation has been one of my favorite
> effects that I have created with CW VTTC's. See:
> http://www.chaoticuniverse-dot-com/webdoc2.htg/Tubez.htm for details of my
> designs. They need a great deal of work, but I can get decent Audio Output
> from the spark. The weak link is the Audio coupling transformer... One day
> I will perfect this, as it does make a very "ear/eye" catching demo.
> 

What you need is a "plate modulation transformer" for an AM transmitter,
which was designed just for what you are doing. They typically are
insulated for several kV (whatever the plate voltage is in the
transmitter), and have a suitable turns ratio to get the P-P output voltage
swing equal to the plate voltage (assuming 100% modulation).  You probably
don't need the voltage, since you are grid modulating, but what you DO need
is the audio bandwidth.  Typical transformers would be used up to 5-10 kHz,
making them quite different from a power transformer optimized for 60 Hz
would be.

Another possibility is the output transformer from a Tube audio amp.  They
run at several hundred volts at several K ohms on the high impedance side,
and 8 or 16 ohms and a few tens of volts on the speaker side.

Finally, you could always string together a bunch of 70.7 V line
transformers, although, I'll bet that would be an expensive way to go.

One source for this sort of thing is Peter W. Dahl Company
http://www.pwdahl-dot-com/... Don't tell them it is for a tesla coil, though,
because they've had problems with coilers in the past.

They have a variety.. For instance, a DX-100 modulation transformer has
primary Z = 8K, 845VCT, secondary 500/2800 ohms -at- 250 mA