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Re: Post from newbie



Original poster: "Steven Ward by way of Terry Fritz <teslalist-at-qwest-dot-net>" <srward16-at-hotmail-dot-com>

Hi Jerry,

well you are a quite experienced newbie i must say!  I have built several 
tube coils so far, and all of them seem to meet or exceed the output of 
other similar coils.  But since i started with absolutley NO experience 
with tubes, i needed to work my way up.  But i did have a good amount of 
spark gap coil experience.  If you havent seen my site yet, it may be quite 
helpful:

http://hot-streamer-dot-com/srward16/

Look at my designs and power used in them.  I also have some theory and 
math pages on there that should help.  Basically, with the AC you should be 
able to overdrive the tube quite a bit, especially voltage wise.  I have 
worked with about 5KV with good results on the 4kv rated 833As.  You may 
also want to consider the staccato circuit (via John Freau;)) on my 
site.  Its very neat, and probably easy enough for you to build.

Basically, if you are going to use more power, you will need to scale 
things up in order to keep the efficiency higher. Also, you will want a 
larger coil to be in the 100-150khz area but not much higher.  Basically, 
you will need to design to your needs (what capacitors are available, size 
of coils, power, etc..).  So you should find the VTTC Math page and VTTC 
notes page very helpful.  You will also need to balance your losses by 
selecting a proper Q value of the tank circuit.  But this is discussed more 
on my website.  The design for the Tetrode will be basically the same as a 
triode, except that you may need to tweak somethings on the grid 
circuit.  Also, as for grid turns, you will just have to experiment and 
find out what you need.  You could measure it, but i never really needed to 
(and never did).  I dont have the equipment.  My highest tech tool i have 
is a 10 or so year old Kikusui 60mhz o-scope, and i didnt use it at all on 
these tube coils.  So you should have a good advantage over me!

Good luck! and please email me with any questions!  I may be able to help.

Steve Ward.





>From: "Tesla list" <tesla-at-pupman-dot-com>
>To: tesla-at-pupman-dot-com
>Subject: Post from newbie
>Date: Mon, 24 Feb 2003 07:50:10 -0700
>
>Original poster: "JERRY ASHLEY by way of Terry Fritz 
><teslalist-at-qwest-dot-net>" <jerryla-at-ix-dot-netcom-dot-com>
>
>Hi,
>
>My name is Jerry.  I have been a ham radio operator for the past 50
>years but I am new to tesla coils.  I just retired and have more time to
>build "stuff".  I have worked as an electronic tech for most of my life
>and have built a lot of ham gear, including transmitters, receivers and
>antennas from the HF bands up through 432 MHz.  Power levels up to 1000
>watts.
>
>I have been reading the mail for about six months but I have not seen
>much info on tetrode tube coils.
>
>I have a 4-1000A tube and would like to try my hand at building a VTTC.
>I plan to use six MOTs wired in series/parallel to give twice the
>voltage and three times the current of a single transformer.  This
>should supply 4 to 5 KV at about 700 mA, close to the specs of the
>tube.  I plan to connect the raw AC directly to the plate tank of the
>tube.  I am going to use the tube in a triode configuration by
>connecting a 10K resistor between the control and screen grid and feed
>the input signal to the screen.
>
>I would appreciate any comments on this design.
>
>Would I need PFC caps on the MOTs?
>
>I have some questions concerning the design of the primary and secondary
>coils.  A ballpark design in this area would help me a lot.
>
>Primary diameter?
>Primary wire size?
>Number of turns?
>
>Secondary diameter?
>Secondary wire size?
>Number of turns?
>
>Number of turns on the grid coil?
>
>Size of grid leak components?
>
>I have some large mica transmitting caps to use in the grid leak and
>primary tank.
>
>Thanks,  Jerry  -  W8UJX
>