It will depend on whether those final amplifier tubes are running in Class
AB1, AB2, or B.  This depends on the idling plate current vs. the key-down
plate current.  Higher efficiency (lower idling current, operating the tubes
closer to cut-off) increases the distortion of your signal, which is
unimportant for CW but quite important for SSB.  I would guess that you are
talking 50 percent efficiency (ratio of power output to power input).  Not
all of the enpower is lost in the tubes, though.  A little of it is also
lost in the pi network output circuit.  I would probably adjust the plate
tuning and loading controls for maximum power output and leave it at that.
I assume you're not trying to run this station remotely.

Lloyd Rasmussen, Kensington, Maryland
Home:  http://lras.home.sprynet.com
Work:  http://www.loc.gov/nls
 
> -----Original Message-----
> From: For blind ham radio operators [mailto:[log in to unmask]]
> On Behalf Of Michael Ryan
> Sent: Wednesday, June 06, 2012 6:44 AM
> To: [log in to unmask]
> Subject: Plate dissipation VS output power
> 
> Hi all:
> 
> Is a rule of thumb to compare plate dissipation to actual output power?
> IE: My FT-102's 3 6146s can safely dissipate 105W between the 3, 200w out
> on SSB and 160 CW. So if I'm running my max CW, whats the plate
> dissipation of the tubes?
> 
> TNX & 73:
> Michael De VO1AX
> 
> Sent from my iPhone