The Minimalist Superhet Radio project.

[Geordie McBoyne]

Hi Trevor,
The simple superhet built on the Premier Radio chassis proved to be very disappointing, perhaps the 6SH7 pentode wasn't up to the job as the anode bend detector. However, the other simple superhet I constructed some time ago was truly excellent. Valves were: UCH42 as FC. 10F1 as the anode bend detector. UL84 output and UY85 HT rectifier. Expect even better performance from an UCH81 frequency changer. 10F1 as detector was OK and the UF80 could also be considered. I'll keep faith with that design and as you state the 4 + 1 superhet doesn't actually qualify for the title of a minimalist superhet receiver.
As an anode bend detector the high slope pentode EF184 should receive serious consideration.
Worth bearing in mind that the earliest Philips Superinductance TRF receivers employed an anode bend detector, a Mullard 994V in UK made sets. 994V is a very high mu triode. If the given figures are correct and the ra is 35K and the gm is 3.6ma/V then the mu is 126, better than an ECC83.

Geordie McBoyne.

[Murphyv310]

At present mine uses an EF91 for anode bend detector. What I'll do is make up a B9A socket to B7G plug adaptor and give the EF184 a try, if successful I'll fit a B9A base as a permanent fitment.

[Murphyv310]

Hi.
As posted on the Radio Caroline thread an EF184 as the anode bend detector has been fitted. This valve has to be the best for the purpose, massive increase in gain. The set works far better than any other short superhet that I've come across.

[Geordie McBoyne]

Hi Trevor,
Do the anode and screen resistors remain at 1 and 3.3Megohms?

Geordie McBoyne.

[Murphyv310]

Hi.
I have 470k on the anode and 2.2m on the screen.

[Murphyv310]

Hi.
Well mine is just about complete. I've fitted a new volume and on off switch, added a 2.2nf cap directly to the IF HT supply pin for improved de coupling, also de coupled the heater supply on the EF184 at the pin, also a little tone correction on the audio output transformer primary. The instability on long wave is cleared and results are really good. All I have to is cut the control spindles and make a simple dial. Only took about four years. All the circuits and original stuff was on VRAT but its strangely all been delete.