[Elecraft] What happened to ALC?

[Walter Underwood]

I expect that ALC is being used for two different parts of the transmission chain.

Audio ALC would reduce the dynamic range of the audio. That automatically reduces the microphone gain to maintain a consistent level of modulation. That would be inside the audio part of transmitter, before the modulator. No external connector involved.

ALC between a transmitter and amplifier does use an external connector. That kind of ALC reduces the transmitter power to try and avoid overdriving the amplifier. It can cause overdriving and splatter.

Unlike the audio version, in amp ALC  the two parts of the control loop (sensor and gain control) are in different boxes, maybe made by different manufacturers. Because the response time and sensitivity of the transmitter gain control are unknown, the system relies on luck to have a stable control loop that doesn’t oscillate. The way to avoid oscillation is to have a slow time constant on the sensor. That means that it just cannot respond quickly, so overshoot will happen and will cause splatter. With audio ALC, the control loop is an integrated whole and can be designed to be quick and stable.

wunder
K6WRU
Walter Underwood
CM87wj
http://observer.wunderwood.org/ (my blog)

> On Jan 30, 2022, at 1:10 PM, Fred Jensen <k6dgwnv at gmail.com> wrote:
> 
> I can remember, shortly after SSB appeared on the ham bands that "ALC" showed up and was immediately inducted into that top category of things like canned beer and sliced bread.  It would reduce the dynamic range of your signal and fill out your RF envelope with DX inducing energy.  It didn't matter if you preferred the James Earl Jones sound by close talking your microphone, or the Storm Drain sound with the gain up and speaking from across the room.  Not to worry, ALC will take care of it for you and you will fully pack your RF envelope.
> 
> Tomorrow is the first day of February 2022 and ALC occupies a less than coveted spot in the same category that also contains last night's broccoli casserole.  One wonders why manufacturers even put connectors and meters labeled "ALC" on their radios.  "Four solid bars, and the fifth barely flashing because the fifth bar is where ALC starts.  Just barely flashing ... you DO NOT want to engage the ALC!"
> 
> I realize that while we believe that the rules of electricity don't change and none of us ever inspect our electricity very closely ... if we did we'd find the power company is selling us used electricity as if it was new ... what changed?  If ALC was slicker than snot back then, why isn't it now?
> 
> 73,
> 
> Fred ["Skip"] K6DGW
> Sparks NV DM09dn
> Washoe County
> 
> 
> 
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