[R-390] QSK; standby reduced fil. voltage; separate B+ on/off

[Roy Morgan]

On Oct 18, 2009, at 6:36 AM, Henry Meils wrote:

> Hi
>
> 1. Does anyone have experience with an alternative idea for full QSK  
> R-390A operation; ie. to avoid the clacking relay noise.

Henry,

If you have an adjustable negative supply you can switch that onto the  
AGC line at the rear of the radio and it will quiet the receiver to  
the degree you want during your CW characters.

> 2. Was thinking of running  always-on reduced standby filament  
> voltage, especially on VFO -

Do you mean during the times you are not using the receiver at all?   
(not reducing the filament voltage during on and off transmitter  
keying.)  I would say that large transmitting tubes, at $1000 to  
$15000 each are very different things than your receiving tubes.   
There is a phenomenon called "cathode interface" that occurs in tubes  
that stay in cutoff condition for long periods of time.  "Computer  
rated" tubes such as the 5963 (like the 12AU7) were developed with  
special cathode coating composition to reduce this effect.  I an not  
sure if low filament voltage would cause this difficulty or not, BUT:   
I ran my Novice days ARC-5 receiver for some years on about half  
filament voltage all the time when it was not running.  The radio came  
alive quite quickly when I turned it on, but I could not see any glow  
in the one tube that was glass.  There seemed to be no harm.

If you run your radio a lot (such as 3-4 hours each day) you may be  
better off running it all the time.

If you run it only some times, I suggest you put in inrush current  
limiters, and use a bucking transformer to get 115 (or 230) volts.

> vy 73s, Henry, OZ1UF-Copen.

I was in Copenhagen a *long* time ago, and had a fine time!

Roy

Roy Morgan
k1lky at earthlink.net
529 Cobb St.
Groton NY, 13073
Home: 607-898-3607
Cell: 301-928-7794