Bill, this is a wild guess on my part and assuming a linear class of
operation:
Bias voltage for triodes is much lower typically than a similar power
tetrode. To achieve a decent power output level, there is going to be quite a
bit
of grid current. As Rich has pointed out many times, grid current is usually
accompanied by rf "feculence".
On the other hand, grounded grid operation automatically provides a large
amount of negative feedback that will mitigate the "feculence" to a large
degree.
When a typical tetrode is operated in a passive circuit, there is usually
zero grid current and the "feculence" is avoided.
Tetrodes operated as grounded grid will benefit from the negative feedback
and grid current can be drawn as a result.
Grid current is related to rf drive power and plate current is increased in
the process. Higher plate current will generate more power output. More output
power is nice only if the signal stays clean. Grounded grid operation helps
with this because of the negative feedback.
73,
Gerald K5GW
In a message dated 2/17/2006 12:35:52 P.M. Central Standard Time,
dezrat1242@ispwest.com writes:
I don't recall seeing any passive grid triode circuits and I'm
wondering why. They always seem to be tetrodes. Is it a neutralization issue?
73, Bill W6WRT
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