[NLRS] Need air variable cap

[Dr. Gerald N. Johnson]

How much voltage does it need to handle? That makes a big effect on 
choices. Then there is no possiblility of 0 to 75 pf. A 75 pf variable 
will be at least 4 pf minimum, more likely as much as 15 pf. The E.F. 
Johnson type S 148-5 is 3.9 to 75 pf with 29 plates about 3/4" wide is 
rated for 850 volts peak with a .013" plate spacing. The type K 158-4 is 
5.5 to 75 pf with 20 plates about 15/116" plates (20 total) with .015" 
spacing . Type S and K are screwdriver adjust only, no shaft for a knob. 
The type R with shaft and 1.5" plates has 17 plates for 8 to 80 pf and 
voltage rating of the standard part of 1200 volts peak. A type D 153-16 
with 0.25" spacing is 25 to 73 pf  with 14 plates over 3" across and the 
capacitor is 6-11/16 long with a 9000 peak volts rating. A type E 
154-13 with 17 plates at 1/8" spacing is  13 to 74 pf at 4500 peak 
volts.  4" long. Plates about 2-1/2 inches across.

If you find a capacitor with a bit too much capacitance you can always 
remove stator plates to lower the capacitance.

73, Jerry, K0CQ

On 9/15/2016 9:15 AM, Art Howard wrote:
>
>
> Still looking for around a 0 to 75pf air variable capacitor.
>    Would like plates to be maybe 1 to 2" wide.
> Thanks
> Art
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