>
>First, RF bias switching does not cause problems when properly
>implemented. So that is a non-issue.
>
? I continue to hear amplifiers with the problem, Tom. When can proper
implementation be explected?
>Second, while Rich focuses on the electronic bias with empirical
>conclusions many rigs have horrid leading edge distortion.
? Leading edge distortion occurs during ALC attack. Leading edge
distortion can be considerable if the operator insists on running the
microphone-gain control at levels that produce high ALC readings.
However, if microphone-gain is reduced to a level that produces little
ALC indication, overshoot is minimal.
>
>..........
>The key to successful auto-bias is NOT pulling the tubes up into
>cutoff, but letting them rest at low dissipation on the class AB side
>of B.
>
>The second key is a bias switch that actuates at milliwatt power
>levels, and that has a response time many times faster than the
>rate of the fastest envelope rise time permitted.
>
? Does it make good engineering sense to wait for RF to start arriving
at the amplifier before beginning the switch to linear-bias? By
syncronizing the EBS with the relays, linear-bias is applied several
milliseconds before RF-arrival. . This is how the high speed switching
circuit in Fig. 7 works. (Fig. 7 is on my Web site)
- later
Rich...
R. L. Measures, 805-386-3734, AG6K, www.vcnet.com/measures
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