[AMRadio] Tube Plate Dissipation Ratings

John Coleman wa5bxo at pctechref.com
Thu Oct 7 12:58:02 EDT 2004

Plate Dissipation is the energy loss in heat to the plate of a tube.  If Ep
= 1000V and Ip = 100 ma = then the total plate input power is 100 watts.  If
the tube is not doing any output but yet drawing the current then the input
power is all dissipated in heat = 100 watts.  On the other hand if the tube
is delivering 60 watts of carrier to a load or antenna, while consuming the
100 watts input, then the tube is dissipating 40 watts in heat = 60%
efficiency.  Special Class C circuits can reach 90% efficiency.

John, WA5BXO

-----Original Message-----
From: amradio-bounces at mailman.qth.net
[mailto:amradio-bounces at mailman.qth.net] On Behalf Of Tom Elmore
Sent: Thursday, October 07, 2004 11:28 AM
To: amradio at mailman.qth.net
Subject: [AMRadio] Tube Plate Dissipation Ratings 

     Can someone please clarify for me the plate dissipation ratings on
vacuum tubes.  I am in the process of restoring a Stancor 60N  that uses a
HK24 tube and the dissipation rating is about 25 watts.  Isn't the 25 watt
rating  Ep*Ip and is this a maximum value that should never be exceeded?  I
believe this transmitter will put out 30 to 40 watts of carrier and if it
were say 60 efficient wouldn't that bump up the plate dissipation to around
65 watts exceeding the dissipation ratings.

Thank You
Tom Elmore  KA1NVZ
Anchorage  Alaska

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