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[Amps] 4cx350f/j's

To: <amps@contesting.com>
Subject: [Amps] 4cx350f/j's
From: 2@vc.net (Rich)
Date: Sun, 17 Nov 2002 07:36:47 -0800
The only diffference is the resistance of the heater,  The W is the same.
Military aircraft and motor vehicles often use 24 - 28V electric systems. 
 

4, 4cx350_s can make 1500W in AB1.  The input circuitry is simpler than 
g-g.   The screen can be supplied from the LV end of the HV bleeder.  
Screen V can be regulated and safely current-limited with a 400V shunt 
zener string.  //  
Since the 350's grid-V is only c.30v, for use with a 200W-max radio, I 
would use a 5.5-ohm grid terminating resistor fed from a 50-ohm in, 9 to 
1 stepdown toroid transformer.   Such a resistor can be made from 18, 
100-ohm, 3W-rated  Matsushita resistors in parallel. (note -- these 
resistors will dissipate 12W each intermittently and they have c. 11nH of 
inductance)  For other than QRPP enthusiasts, anode supply potential 
should be 2500VDC under load for CW/RTTY/FM/AØ -- and it could be a bit 
more for SSB.  Anode-current for 4-tubes should not exceed 1.2A - except 
for those who have more money than brains.  A transformerless grid bias 
supply can be made by half-wave rectifying one side of the mains and 
resistive-dividing the resultant -160VDC down to c. -30V on TX and c. 
-60V on RX.  This does not need to be regulated since there is zero 
current consumed.

>Any of you fellas ever apply these to a project for amateur amplification? 
>Is 
>there any disadvantage to the 26.5 volts on the heater, or does it just heat 
>quicker? Not much info on Rell's page via Richardson's Electronics. Let me 
>know.
>Paul..



-  Rich..., 805.386.3734, www.vcnet.com/measures.  


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