UK Vintage Radio Repair and Restoration Discussion Forum - View Single Post

G8HQP Dave · 2nd Jul 2019, 2:39 pm

The EF92 is not a vari-mu version of EF91; it has much lower transconductance for a start. The two valves are not really related at all. The EF92 could be considered as being either
1. a miniature version of some octal RF pentodes such as 6K7
2. an EBF80 with no diodes

I suspect that the EF92 was developed when someone realised that there is more to valve and circuit design than raw gain, and that the requirements of an RF/IF pentode for AM and other narrow-band systems can be quite different from wideband systems like TV, FM and radar.

2nd Jul 2019, 2:39 pm	#19
G8HQP Dave Rest in Peace Join Date: Sep 2008 Location: Solihull, West Midlands, UK. Posts: 4,872	Re: EF91 to EF80 The EF92 is not a vari-mu version of EF91; it has much lower transconductance for a start. The two valves are not really related at all. The EF92 could be considered as being either 1. a miniature version of some octal RF pentodes such as 6K7 2. an EBF80 with no diodes I suspect that the EF92 was developed when someone realised that there is more to valve and circuit design than raw gain, and that the requirements of an RF/IF pentode for AM and other narrow-band systems can be quite different from wideband systems like TV, FM and radar.