[ARC5] BC-453 drift test

[Kenneth G. Gordon]

On 11 Jan 2018 at 9:38, DSP3 wrote:

> I certainly concur.  I run 4 receivers and use a nominal B+ of about 
> 160v.  Current measures about 40ma, max.  There is no measurable 
> drop in anything except perhaps total audio output power, certainly 
> not sensitivity or BFO operation.  The R-25A is used as a tunable IF 
> for the ARC-2 and, as performed by others, find drift after a nominal 
> worm-up time to be very, very low.  Granted, digital usage is not a 
> consideration at this QTH.  That said, I also run B+ on BC-348 
> receivers, et al, at about 180v with, again, no degradation. 
> Jeep - K3HVG

As I have mentioned more than once here, I have found, after much experimentation, that 
our receivers seem to work best at a voltage of about 180 VDC.

However, I also found that moving the screen voltage lead from the junction of the two big 
black resistors in the rear to the "hot" end made a significant improvement in sensistivity 
without degrading drift.

Looking at the specs for the 6/12SK7 tubes, we find that 180 V is "about right" for those 
tubes' screen voltage. Typical specs are 100 V, but that would require changing resistor 
values, and I believe in the KISS principle.

Ken W7EKB

---
This email has been checked for viruses by Avast antivirus software.
https://www.avast.com/antivirus