[ARC5] Quick sensistivity comparison

[Geoff]

> RF gain max. AF gain low. Radio Shack CB speaker with 500:8 ohm 
> transformer. Audio
> impedances are not properly matched, but there is still ample audio.
>
> 12SH7: AM 0.3 microvolt modulated 400 Hz at 30% clearly heard.
>             CW 0.1 microvolt clearly heard.
>
>
> 12SK7: AM 1 microvolt, same conditions as above, heard mixed with noise
>             CW 0.3 microvolt, heard, mixed with noise
>
> Signal generator: HP-8640B fed to receiver through a 50 ohm terminator.
>
> I must admit to being surprised.
>
> Ken W7EKB


No surprise at all when you compare a low performance remote cutoff pentode 
with a sharp cutoff tube with 2X+ the transconductance.

If you want an apples to apples comparison then use a  12SG7 making socket 
changes as/if needed for the.

I suspect there are other issues involved with that radio if you can hear a 
difference on an antenna that isnt a low noise type.

Carl