The National Cap

Unfortunately this cap is not the right cap for a SML because it uses a wiper contact, a f$T2eC16ZHJHUFFf(uEbsyBRr+qqG6ow~~60_57act I did not pick up on.  The other problem is that it is impossible to tune easily.  At 14070 mhz for example, the angular rotation is in th hundreds of khz per degree so the 10 khz resolution required is an imperceptible change.

The first cannot be fixed, so the cap is going to be lossy.  I’m thinking this could be OK for receiving but for operations…. I guess we’ll see.  The MFJ cap may or may not ship, (they have $100 of my money),  A gear reduction drive should fix the second problem.  Using an RC car gearbox, I may be able to get 14:1 wchich translates roughly into 8khz per degree of ratation of the pinion gear … this may be sufficient resulution …. but it shows the importance of a gear train for capacitors.


If the stator was cut in half, the cap becomes two variables in series … hmmm.  Makes more sense to find another high V cap to place in series with this one …

~ by marksun on July 30, 2013.

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