[R-390] Nuvistaplug? Other possible tubes.

[Kenneth G. Gordon]

Mark Huss wrote:

> The installation manual and schematic is here: 
>
> http://www.mines.uidaho.edu/~glowbugs/receivers.htm 
>
> see item number 7.
> I figure you can either use it unmodified (will have to substitute 
> 6CW4's for the 6DS4's, because the 6DS4's won't handle the higher B+ 
> voltage) and sacrifice AGC control of the first RF Amp, or you can 
> rewire pin 8 of the first 6DS4/6CW4 to connect to the unused pin 2 of 
> the seven-pin plug to restore some AGC operation.
>  In 2004, W3CRR was going to build one, and wondered if there was any 
> interest in copies.
> Now, the 6CW4 has a higher noise than the 6DS4, but the 6DS4 is rated 
> for only 135VDC plate voltage.  Can any tube gurus out there tell us if 
> using a 6DS4 as the first tube and a 6CW4 as the second would be safe?  
> This might give a better noise figure than two 6CW4's.
> Further thought tells me that most receiver locations would have an 
> ambient noise at their location to make this no real improvement except 
> above 20 MHz.

I am thinking that a better, much lower-noise, Nuvistaplug could be 
made using a single 7963 submini dual triode instead of the Nuvistors.

The 7963 has far higher transconductance, 13000, than either of the 
two Nuvistors mentioned. However, its maximum rated plate voltage is 
only 100 VDC, so allowances would have to be made for that.

Go here:

http://pw2.netcom.com/~wa2ise/radios/penciltubes.html

for details on submini tubes.

And thanks for the plug to the Glowbugs web site. I administer that.

Ken Gordon W7EKB