SB-401 VFO Tube

[Kenneth G. Gordon]

On 10 Apr 2010 at 7:36, Jim Schnurr wrote:

> I have two SB-401 transmitters I am working on. They both had a 6CB6A
> tube in the LMO unit. The book calls for a 6BZ6 .  The first one which
> I now have working I  replaced the  6CB6A with the 6BZ6 and it is
> doing fine. Any reason for using the substitute tube 6CB6A as I have
> both  on hand to utilize. ?

Simply use what ever is available.

The 6CB6A is a sharp-cutoff pentode, while the 6BZ6 is a remote-cutoff 
pentode. The 6BZ6 is a "preferred substitute" for the 6CB6A.

Both have identical basings, and their internal capacitances are very 
similar.

Listed transconductances are identical.

The 6BZ6 was used by Collins and Hallicrafters, at least, as a receiver 
RF amplifier tube as it proved to have lower noise and more resistance 
to overload than the 6CB6A.

The 6BZ6 was also designed much later (as I understand it), and 
therefore, in my opinion, would be the preferable tube as it would 
probably be more reliable.

Ya pays yer money and ya takes yer choice.

BTW, I think the SB-401 is an excellent transmitter.

Ken Gordon W7EKB

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