Follow along with the video below to see how to install our site as a web app on your home screen.
Note: This feature may not be available in some browsers.
Hi,
I know you talk about the core..
But coating plastics have big influence on temperature stability.
Two component plastics are worse.
--> try to use coils without coating.
Klaus
For a very stable VFO you need a ceramic former with the coil turns sintered on to it. This is so the turns cannot move because they are "stuck" to the former. As copper expands with rising temperature, the whole coil "grows" as the temperature increases. Plastics exhibit a terrible temperature coefficient. You could look up to see what glass is like and wind you coil on a glass tube.
FWIW The VFO had a mechanical digital counter as the digital display. This was so that you could freely tune like a conventional receiver, then transfer the mechanical reading to the digital knobs and switch to digital and the station would still be there+- 20HZ.
Frank
- - - Updated - - -
Just been thinking, if you physically match the diameter against the length. You should be able to get the temperature coefficient to be zero. if the coil is short and fat, the increase in diameter will increase the inductance as the temperature rises, if its long and narrow the inductance will decrease as the coil gets longer. From the depths of my memory, I think it might be about 5:1 (length to diam).
Frank
Hi,
Is an air coil better in terms of temperature stability, as compared to a ferrite or powdered toroid?