[AMPS] Re: [DX] 3CX3000F1

Rich Measures measures@vc.net
Sun, 28 Sep 97 12:31:59 -0800


>At 11:22 AM 9/28/97 -0500, you wrote:
>>On Sun, 28 Sep 1997 18:39:45, Nick, VK9LX wrote:
>>
>>>My apologies for  being  off the topic...
>>>Can any one tell me please what is the difference between
>>>3CX3000F1 and 3CX3000F7?
>>>I would like to hear from someone who has used this or similar
>>>tube in hf pa.
>>>Is there any 'reflector' devoted to hf amplifiers on the Internet?
>>>Nick

 __________________________________________________________________
>>I am also interested in the same answer!  Rich, Tom, Carl?

-   I did not receive the original post.  //  As far as I know, the 
[AMPS] mailing-list seems the best such thing going on the Internet.  
Linear amplifiers are also discussed on rec.radio.amateur.homebrew 
Newsgroup.  However, the problem with Newsgroup discussions is that they 
move along slowly.  An example is Phase 1 of the vhf parasitics debate -- 
which moved at a snail's pace between the end of last October and the 
beginning of last March..  However, Phase 2 of the debate took place at a 
delightfully faster pace on the [AMPS] mailing-list.
-  Edtorial Opinion: ....  The potential fly in the ointment with a 
mailing-list is a moderator with an agenda, or a moderator who listens to 
cry-babies whose favorite guru is getting himself into deep feculence.    
 
-   The A/F1 is designed for grid-driven linear amplifier service.  The 
A/F7 is designed for cathode-driven linear amplifier service.  Although 
the F7 and A7 work well in cathode-driven HF linear service, the F1 and 
A1 are somewhat impractical for use in grid-driven HF linear service.  
The problem is that over 1000v is needed to drive the grid.  Up to a few 
hundred kHz, such driving potentials are not impractical.  At HF, they 
are.  ....... I have never heard of an HF linear amplifier that uses the 
3CX3000A1 or F1.  So why not select the 3CX3000A3 instead, so that less 
driving potential would be needed? - - - Because the only triodes that 
are usuable in Class AB1 grid-driven linear service have a Mu of 5 or 
less.  Why?  Because only the low Mu variety is capable of producing the 
required high, peak anode current at the required maximum of zero grid 
volts.  //  Similarly, only high Mu triodes are suitable for 
cathode-driven linear service.  Low and medium Mu triodes would work, but 
the driving volts and watts needed is not practical.  How many people 
would be interested in building a linear amplifier with extra low gain?   
>
>From the Varian Power Grid Tube Catalog:
>
>                        3CX3000A1/8238       3CX3000A7
>                        3CX3000F1/8239       3CX3000F7/8162
>
>Plate Dissipation:                4000                 4000
>Grid Dissipation:                   50                  225
>Filament            Thoriated Tungsten   Thoriated Tungsten
>   Voltage                         7.5                  7.5
>   Current                        51.5            51.5/50.5
>Amplification                        5                  160
>Transconductance                11,000
>Max ratings
>   Plate Volts                    6000                 5000
>   Plate current                   2.5                  2.5
>
>Typical Operation      AB1 Grid driven               AB2 GG
>   Plate Volts                    5500*                4800
>   Plate Current                   2.2*                 2.0
>   Drive Power                       0                  410
>   Power Output                   8250*                7260
>
>                            * two tubes
>
>Note: The A1/F1 versions are coaxial base tubes 
>      The A7/F7 versions have filament and grid leads
>
According to Eimac, the A1 and A7 do not have wire leads on the coaxial 
base.  The F1 and F7 have wire leads attached to the coaxial base.  
>
>73, 
>
>   ... Joe Subich, W8IK  ex-AD8I
>       <w8ik@ibm.net>
......................

Rich---


R. L. Measures, 805-386-3734, AG6K   


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