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On 9/4/15 12:10 PM, Matthew Sweeney wrote:
So after all these years of static generators I've decided to build a
really decent coil. I know some electronics but not much high power RF so
probably a spark gap. I've looked online in my various books and find a lot
is disagreement about primary tank arrangement, use of inductors and
'squenched spark gaps'.
I don't need and entire plan but I'd be delighted for some simple tips for
my design:
Easy enough.
How big a coil? NST powered? MOT? Pig?
Sparkgap or Solid state.
I'm going to assume sparkgap
* what type of secondary wire where to buy
eBay or Amazon
I find that AWG30 is way too small, AWG16 is probably too big..
Somewhere in the middle is easy to wind. AWG24 is a convenient size.
Look up in a wire table how many feet per pound you get, and you can
order 1 pound or 5.
A motor rewinding shop will often sell you wire by the pound, if you
want to do it retail.
* ideal secondary form material (I used pvc in the past).
PVC is good
* good place for decent HV caps for the long series/parralel type (do I
need resistors for these).
The usual mail order places, mouser, digikey, allied, etc.. The prices
and availability change on a day to day/week to week basis. I've
noticed serious price anomalies where stringing 1.6kV units was actually
cheaper than 2kV units.
* primary winding material/type I've used copper tube inclined out I see a
lot of recent coils just wind straight up with thick solid insulate wire?
I like flat primaries: easy and gives good field control. Cylindrical
primaries tend to have too high coupling which gives you a racing spark
problem. Cones aren't worth it, IMNSHO
You can prototype with AWG 12 house wire and then change to copper
tubing when you get it working.
* best design for primary tank like arrangement of gap/caps.
I like spark gap shunt across transformer, single C in series with
primary L.
* feedback prevention.
* where to find a decent affordable variac. I've seen people using light
dimmer switch this seems insane!
Why not? If it works.
* I have 12k,12k,15k 30ma old francefoormers.
You can gang them up in parallel.
* I do have a scope but no frequncy generator. Could I literally use my
computer/phone with a simple unamplified sine generator.
You can tune by running the apps to get close, and then basically do the
traditional "tune for maximum length".
* rotary slark gap? Is it worth it, what troubles does it bring?
I've always used static and/or triggered gaps. I'll let others comment.
For a NST, a static gap is easy. Make it something that is easy to cool.
Thank you so much for any info as noted I'm checking online too but this
group seem to have major experience.