[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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