[Amps] 1 tube or two ??

TexasRF at aol.com TexasRF at aol.com
Sun Feb 11 15:08:16 EST 2007






Jim, by all means there is an advantage of running a single tube over two  
tubes; in fact there are several in your case:
1> less filament power/lower electric bill
2> no losses in getting drive power split and output power combined  
properly. While these losses are small, they are present.
3> You do not have to own two tubes to operate; sell one on ebay and  pocket 
the $$
4> no worries about matching tube characteristics. Not a real issue in  
practice, but is a consideration when running well used tubes.
5> no worries about balancing cooling air flow. Not a big deal, but is  a 
consideration.
6>linearity is influenced to a degree by the idling plate current. Two  tubes 
will consume 2X idling current and power,  increasing your electric  bill. 

One other respondent mentioned 3 dB  more output power for two tubes but in 
your case, this is not correct. The  amplifier will have essentially the same 
gain in dB for one vs two tubes. This  happens because the drive power is 
divided between the two tubes, losing 3 dB  and the output powers are combined, 
gaining 3 dB. Net power is the same less any  divider and/or combiner losses. 

 
73,
Gerald, K5GW
 
 
 
In a message dated 2/11/2007 1:16:45 P.M. Central Standard Time,  
jim.isbell at gmail.com writes:


It  seems no one really read my question.

"Is there an advantage of one  over the other if both are run at the
limit for the Ham Bands?"

I  clearly stated "at the limit for Ham Bands."  Therefore two  tubes
does not have an advantage in power.  Both circuits can run at  maximum
legal limit without strain.

Now is there an answer to the  original question???


On 2/11/07, kenw2dtc  <kenw2dtc at comcast.net> wrote:
> "running at full tilt, the  two-tuber would have a whopping(!) 3 db.
> advantage over the single  4-1000A!
>  That's a full half S-unit difference"
>
>  That's  a true statement.  Interesting that in today's world of  inflated
> S-meter readings with circa 2004-2007 receivers it may  be  impossible to
> double the power and get just a half an  S-unit meter change.
>
> 73,
> Ken  W2DTC
>
>
>


-- 
Jim Isbell
"If you are  not living on the edge, well then,
you are just taking up too much  space."
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