John L Stewart wrote:
'Alejandro Lieber[_3_ Wrote:
;963267']I am thinking in building an AM transmitter for 7.1 Mhz (40
meters) using a
EL34 in class C as final.
The idea is to modulate it by varying the negative polarity of the
suppressor grid (g3).
Suppose I load the EL34 plate with 500 volts DC and a current of 150 ma
with
0 volts suppressor, does anyone have any idea what negative voltage in
g3 is
needed to reduce the anode current by half, needed for screen AM
modulation ?.
Alejandro Lieber LU1FCR
Rosario Argentina
Real-Time F2-Layer Critical Frequency Map:
http://1fcr.com.ar
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As the G3 voltage is biased negative the G2 current will increase in
proportion to the decrease in anode current. That can result in a
dangerous increase in screen dissapation. To prevent that, the screen
needs to be supplied thru a limiting resistance. Refer to the attachment
lifted from FE Terman.
I have discovered that the 2E22 like the 803. both built for suppressor
modulation, are capable of very high screen dissipation, as very high screen
current appear when the suppressor is very negative polarizes.
--
Alejandro Lieber LU1FCR
Rosario Argentina
Real-Time F2-Layer Critical Frequency Map:
http://1fcr.com.ar
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news://freenews.netfront.net/ - complaints:
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