Oscillators

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Re: Oscillators

Post by Admin on Sun Dec 25, 2016 12:20 pm

Hi Jalex2
Funny you should mention this, but I tried making some loooong air-spaced coils, and then measuring the inductance/length. It did not seem linear. If you use the same coil with a tap then the % tapping is not the percentage of the complete coil you think it is, since the mutual coupling between turns is not a constant.

I also had a similar experience when trying to match an HF antennausing tapped coil/capacitance.

My conclusion is that coils should be relatively short, relative to the Diameter, especially for single-layer coils.

Anyway, Merry Christmas to you.
BR Harry
EA/SM0VPO

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Oscillators

Post by Jalex2 on Sat Sep 10, 2016 5:12 pm

Hi Ivan
Are you sill here?
I haven't been here for a long time as I have been busy.
How have you been?
I was just wondering something.
I built Harry's Simple RF oscillator using all the parts as he specified and it didn't run.
I wound the coil  on a toroid from a fluorescent light bulb and it measured 200uh.
I think those are high perm. 
Any way I put the same configuration on a CD4011 inverter and it worked fine
at about 2 mhz.
 There seems to be a lot of difference between air wound coils and toroid wound coils
when it comes to oscillators. Can you explain a little about this?

Jalex2

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