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G6Tanuki · 24th Oct 2019, 7:48 pm

On the EF91 vs EF80 game, yes I can see the benefits that accrued from going to the B9A base (more cathode-connections/better cathode-decoupling) which would become really rather more-important a few years later when we got the high-slope "Frame Grid" EF183/EF184 - hich gave more-than-enough gain at TV-IF frequencies that you could happily cut down the number of valves used in the IF-strip.

In the context of 'consumer vs industrial' range kit, I remember the likes of the 1950s Burndept BE201 transceiver - covering 100-156MHz (AM) which used EF91 in the front-end, and also a number of fixed-tuned military 121.5MHz 'watch' receivers from the same era that used the 6AK5 for the RF-amp and mixer. The EF91s used were generic Mullard ones with the blue coating on the inside of the envelope, whereas the 6AK5s were US-sourced from Tung-Sol or National.

24th Oct 2019, 7:48 pm	#67
G6Tanuki Dekatron Join Date: Apr 2012 Location: Wiltshire, UK. Posts: 13,998	Re: EF91 to EF80 On the EF91 vs EF80 game, yes I can see the benefits that accrued from going to the B9A base (more cathode-connections/better cathode-decoupling) which would become really rather more-important a few years later when we got the high-slope "Frame Grid" EF183/EF184 - hich gave more-than-enough gain at TV-IF frequencies that you could happily cut down the number of valves used in the IF-strip. In the context of 'consumer vs industrial' range kit, I remember the likes of the 1950s Burndept BE201 transceiver - covering 100-156MHz (AM) which used EF91 in the front-end, and also a number of fixed-tuned military 121.5MHz 'watch' receivers from the same era that used the 6AK5 for the RF-amp and mixer. The EF91s used were generic Mullard ones with the blue coating on the inside of the envelope, whereas the 6AK5s were US-sourced from Tung-Sol or National.