UK Vintage Radio Repair and Restoration Discussion Forum - View Single Post - Ge or Si transistors - any stability-difference if used in a VFO?

G6Tanuki · 14th Mar 2019, 3:31 pm

I'm looking at building a 'classic' Vackar-style transistor VFO that will be operating around 3MHz and be powered from a 12V supply (suitably stabilised).

The circuits I've seen in 1960s RSGB and ARRL books - some use Ge transistors, some Si.

I've got both (no, whiskery AF11x-series are not included!) - are there likely to be any stability-benefits/disbenefits in going for Si over Ge? Or will any difference be more down to the physical characteristics of the particular transistor's encapsulation? I'm thinking of clamping the transistor-case to the case of the VFO-box to provide a smidgin of thermal-inertia.

14th Mar 2019, 3:31 pm	#1
G6Tanuki Dekatron Join Date: Apr 2012 Location: Wiltshire, UK. Posts: 14,007	Ge or Si transistors - any stability-difference if used in a VFO? I'm looking at building a 'classic' Vackar-style transistor VFO that will be operating around 3MHz and be powered from a 12V supply (suitably stabilised). The circuits I've seen in 1960s RSGB and ARRL books - some use Ge transistors, some Si. I've got both (no, whiskery AF11x-series are not included!) - are there likely to be any stability-benefits/disbenefits in going for Si over Ge? Or will any difference be more down to the physical characteristics of the particular transistor's encapsulation? I'm thinking of clamping the transistor-case to the case of the VFO-box to provide a smidgin of thermal-inertia.