[TenTec] Re(Ten Tec) In praise of older technology

[Rick - DJ0IP / NJ0IP]

Jim,

When you say back off the plate current... I hope you mean back it off by
applying less drive.
Backing it off using the load control would be wrong, and cause splatter.

Also, I have been tuning my AL-80A for peak for 30+ years and the power has
dropped from a little over 900w out down to about 800w out. Still the
original tube. 

The easiest way to avoid expensive tube replacement is to buy an amp with a
tube or tubes which are forgiving when you make a mistake.  The glass tubes
all were, the ceramic tubes mostly are not.

AND always monitor grid current on the glass tubes.
As long as you do not exceed Ig maximum rating, you will probably never blow
the tube(s).

73 - Rick, DJ0IP
(Nr. Frankfurt am Main)


-----Original Message-----
From: TenTec [mailto:tentec-bounces at contesting.com] On Behalf Of JAMES
HANLON
Sent: Sunday, March 02, 2014 6:38 PM
To: tentec
Subject: [TenTec] Re(Ten Tec) In praise of older technology

On the question of tuning for Dip versus tuning for maximum output, let me
offer a few words of, I hope, wisdom.
 
First, the additional amount of power output that might be obtained by
operating the rig "off dip" is so little that it will make absolutely no
difference at the receiving end.
 
Second, you are very likely increasing the total amount of power dissipated
in the final amplifier tubes by operating "off dip," and you are pulling
more current from the tube cathodes as well.  Both will contribute to
degrading the amplifier tubes' life.  Considering what replacement tubes
cost these days, you probably don't want to shorten the life of your
existing tubes in order to get a few watts more output from them. 
 
You would probably be better advised to run the amplifier at somewhat less
than full, ICAS class C ratings, that is to back off the fully loaded plate
current a bit.  You would lose at most one or two dB on the other fellow's
S-meter, and you would add considerably to the life of your tubes.    
 
Jim Hanlon, W8KGI
 		 	   		  
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