[AMPS] Re:Question: input Z on class AB gnd grid pair 4-400 ??

[measures]

>
>Jan.E.Holm@telia.se wrote:
>> 
>> With 100W drive and 3kV on a pair of 4-400īs it might
>> be a problem to get 1500 out, better run 4 kV on plates.
>> I have a 3 tube 4-400 amp 10 - 160m and it runs excelent.
>> After 20 years of service it still runs full output and
>> the tubes wasnīt even new back then, I run slightly less
>> then 4kV on them and they are GG. If you have the hardware
>> for a 3 tuber thatīs the way to go.
>> 
>> 73, Jim SM2EKM
>> 
>> PS: You can use the same tuned input as a SB-220 (or similar)
>>     uses and just tweak it.
>
>Hi Jim,
>
>Thanks for the reply.  Your idea of a 3 holer sounds neat.  I wasn't
>expecting to get more than 1200 watts out from a pair of gg 4-400's.  I
>think that's about all you can do assuming 60% efficiency in class AB
>without exceeding their plate dissipation.
>
>I'm curious what values you used in your tank circuit.  The problem that
>I see with 3 tubes is the increased Cout (plate to gnd) that the pi-L
>network will see.  It's probably not a problem on 160 through 40, but
>the Q of the network must be pretty high on 10m.

€  With three tubes vs. one tube on 10m, you need three times as much 
C-tune to establish the desired Q.    Another old wives' tale of amateur 
radio bites the dust.    
>
>BTW, the bottles that I will be using are the pulse rated version of the
>4-400, the 4PR400A (8188).  I have 5 of them.
>
€  I would not hesitate to run up to 5kV on SSB, Charlie    Output should 
be about 1100w per each, pep.  Dissipation would be about 650w.  Key-down 
tuneup would, of course, be nutz.  // .  The SB-220 clearly has The 
cooling system that produced the lowest envelope temperature.  

good luck.  

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


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