Peter - -
>Rich says:
>
>>? The weaknesses in the transceiver's ALC are automatically taken into
>>account by adjusting E-grid so that virtually zero current flows when
>>max. drive is applied. I contend that it is important Not to
>>subsequently change the E-grid adjustment for any other purpose.
>
>
>Hmmm. I guess that firstly, we need to define our aim.
>
>I think that Rich is saying that we mustn't draw grid current,
? indeed
>and to that
>end, the bias and input swamp resistor must be set correctly, and the screen
>voltage set for the standing current.
? yes
>On the other hand, I'm saying that the
>voltages should be set correctly and the drive set such as not to draw grid
>current.
? The sticky wicket is a means of thwarting transceiver overshoot. With
my method, the extant overshoot is taken into account by firstly setting
E-grid so that virtually no grid current flows.
>
>I suspect that unless you are prepared to take some care, Rich's answer may
>be more practical if you are pushing up to the maximum output that the tube
>is capable of.
? Why pay good money for a tube and not utilize it's emissive capability?
However, one should not use more power than is necessary to
communicate. Power adjustment can be easily achieved by adjusting the
microphone gain control. My guess is that fewer than 0.001% of CBers and
fewer than 2% of hams would even consider deliberately turning down
microphone gain.
>
>However, if you can start the ALC a long way before the tube even considers
>drawing grid current, then ALC will do the trick - provided that the open
>loop gain is not too high, so that you are winding the exciter gain back by
>say 3 or 4dB, no more.
? good luck.
>Or that you keep an eye on the drive level - y'know,
>actually know what you're doing.
>
>The old Marconi autotune tx's switched in an attenuator in 1dB steps, and
>used a servo motor driven attenuator to interpolate: it tuned up on carrier
>to PEP, adjusted the drive level with the servo motor and relays, and that
>was that. No ALC.
? However, then one needs two more high-speed relays to switch said attn
in and out between RX and TX.
>...
- cheers, Peter.
Rich...
R. L. Measures, 805-386-3734, AG6K, www.vcnet.com/measures
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