[AMPS] E F Johnson Roller

[km1h@juno.com]

On Thu, 07 Jan 1999 21:41:04 -0800 Arne Gjerning <gjerning@flash.net>
writes:
>
>I had a caliper and Johnson model 226-1 handy. The ribbon coil is .125 
>x 
>.250 silver plated copper. This model has 5 turns wide spaced and the 
>
>remainder close spaced. Johnson made other models besides this one.
>
>I was asked at one time why an amp using a roller coil arced. If 
>unused 
>turns are not shorted out a transformer is created. Depending on where 
>
>the coil is tapped the open end can develope a rather large voltage 
>(rf) 
>and really play havoc inside an amp. ALWAYS SHORT OUT UNUSED TURNS OF 
>A 
>TANK COIL, whether a roller or switched circuit.


Unshorted turns can result in a Tesla coil effect...lots of arcs!  But
shorted turns can result in a closed loop resonant tank circuit and also
arcs.

So where do you draw the design line?

Several have suggested BIG components. Several manufacturers have had
reliable products with either switch configuration.

73  Carl  KM1H





>
>Many roller coils by numerous manufacturers are made differently. I 
>have 
>about 4 differnet types of large roller coils, most use ribbon and 
>several use wire (round). BTW, NOT FOR SALE. Will be using several.
>
>73 de Arne N7KA
>
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>

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