[ARC5] BC453 on 24V - screen voltage

[Bill Cromwell]

Hi Dennis,

I use the 9-volt battery stacks with mine and the gel cells for heaters 
the same way. There is enough band noise that maximum possible 
sensitivity isn't all that important. Going too low may affect overload 
susceptibility. I run my B+ at 90 volts and have no problems. I started 
doing that in an attempt to reduce noise conducted from the power lines 
through a power supply into the receiver. It made a worthwhile 
improvement. The rest of the benefits are just gravy:)

I may try disconnecting that screen bias ground lug, too.

73,

Bill  KU8H


On 12/10/19 12:51 PM, Dennis Monticelli wrote:
> Actually, floating the ground lug leaves the screens hard connected to 
> B+ via the top resistor in the divider.  That's OK.
> 
> I will add here that a string of 9V batteries works well for reduced B+ 
> operation and has the added advantage of less supply coupled noise.  If 
> for example a string of 7 nine volt alkaline batteries are used, the net 
> B+ current is only 5mA (with the bottom lug of the screen divider 
> lifted) , which translates into 100 hrs of operations.  I have run my 
> BC-453 this way and even taken it into the field (gel cells for the 
> heaters).
> 
> As for the minimum practical B+ voltage, I have found that the first 
> circuit to collapse is the LO.  Sometimes running down to 28V kills that 
> oscillator, sometimes it doesn't.  Obviously the gain will be way down.  
> I have found that around 60V gives decent operation.  More of course 
> would be better for gain reasons but S/N doesn't improve much further, 
> which is what we mostly care about.
> 
> Dennis AE6C
> 

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