22-08-2013, 12:20 AM
Yes, Lawrence, an interesting read, even if it is a bit heavy. 
I've never heard of Lampkin, let alone an oscillator named after him.
As regards frequency stability of variable frequency LC oscillators, in Amateur Radio circles the traditional approach was - and I think still is - to take appropriate measures to prevent changes only to the inductance of the coil, this one single component contributing the greatest effect on frequency stability compared to all the other components comprising the whole LC oscillator. Usual approaches were akin to a traditional crystal oven, but instead of a crystal within that temperature-controlled chamber, the coil was thus situated.
Having said that, one novel attempt to compensate for frequency change with temperature became available to Radio Amateurs back in the '70's. I do recall Oxley Developments manufactured a device called a 'tempratrimmer', which, if memory serves me correctly, was an adjustable capacitor whose rate of change of capacitance with temperature could be manually adjusted. I suspect that Oxley have long since finished trading and that device has gone with them. Should anyone know otherwise, I'm sure that they'll let me know - and if so, is that device still available?
Al. / Aug. 21, 2013 //
I've never heard of Lampkin, let alone an oscillator named after him.As regards frequency stability of variable frequency LC oscillators, in Amateur Radio circles the traditional approach was - and I think still is - to take appropriate measures to prevent changes only to the inductance of the coil, this one single component contributing the greatest effect on frequency stability compared to all the other components comprising the whole LC oscillator. Usual approaches were akin to a traditional crystal oven, but instead of a crystal within that temperature-controlled chamber, the coil was thus situated.
Having said that, one novel attempt to compensate for frequency change with temperature became available to Radio Amateurs back in the '70's. I do recall Oxley Developments manufactured a device called a 'tempratrimmer', which, if memory serves me correctly, was an adjustable capacitor whose rate of change of capacitance with temperature could be manually adjusted. I suspect that Oxley have long since finished trading and that device has gone with them. Should anyone know otherwise, I'm sure that they'll let me know - and if so, is that device still available?
Al. / Aug. 21, 2013 //
