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Bazz4CQJ · 13th Aug 2019, 1:17 am

For some reason, the design of this GDO is something that I come back to at periodic intervals. It was made in the early 60's, used a tunnel diode (TD) with no useful ID as the oscillator and 3 Ge transistors as a meter amp, all running from single AA battery.

Although TD's went out production a long time ago in the West, there are lots of Russian TD's for sale on line. Most of these are described as 'switching" diodes, a few as 'amplifier' diodes and just a small number are described as 'oscillator' diodes. I'm unsure as what significance to put on these designations; what would be the major difference between them?

One parameter that would come in to play in an oscillator circuit would be the capacitance of the diode and quoted values of 10-20pF seem common. That value will obviously limit the upper frequency limit.

Anyone got any insights on this?

B

13th Aug 2019, 1:17 am	#1
Bazz4CQJ Dekatron Join Date: Apr 2009 Location: Oxfordshire, UK. Posts: 4,934	Heathkit GDO using a Tunnel Diode For some reason, the design of this GDO is something that I come back to at periodic intervals. It was made in the early 60's, used a tunnel diode (TD) with no useful ID as the oscillator and 3 Ge transistors as a meter amp, all running from single AA battery. Although TD's went out production a long time ago in the West, there are lots of Russian TD's for sale on line. Most of these are described as 'switching" diodes, a few as 'amplifier' diodes and just a small number are described as 'oscillator' diodes. I'm unsure as what significance to put on these designations; what would be the major difference between them? One parameter that would come in to play in an oscillator circuit would be the capacitance of the diode and quoted values of 10-20pF seem common. That value will obviously limit the upper frequency limit. Anyone got any insights on this? B __________________ Saturn V had 6 million pounds of fuel. It would take thirty thousand strong men to lift it an inch.