[Elecraft] What happened to ALC?
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 -- This email has been checked for viruses by AVG. https://www.avg.com __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to arch...@mail-archive.com
[Elecraft] What happened to ALC?
I'll show my age by doing this, but lets revert mentally back to the Collins S Line. The transceiver, using a pair of 6146's in the PA, was most efficient and linear when properly tuned and loaded. It produced about 120 to 140 watts of PEP output. And there was NO Power control or method to reduce the power as we know it today. Introduce the 30L1 linear amplifier, being 4 x 811's, which required about 60 to 80 watts of drive to reach maximum rated output. So the issue now is, how do we get the properly tuned and loaded transceiver down to the correct drive level for the 30L1? ALC is the Collins answer. Thus the voltage determined by the amplifier grid current was fed back to the inter-stage of the driving transmitter to effectively reduce the output while still retaining the correct tuning and loading of the transceiver PA. Today it seems that the designers have monkeyed around with the time constants in the ALC algorithm to improve certain aspects of the signal, thus reducing key clicks and overshoot, but seemingly at the sacrifice of certain other areas of the signal. Thus we find that ALC is not to be used to control power or raise the average power but designed to prevent over drive of any stage. Correctly, Speech Processing is deemed much more effectively used and with less undesired effects on speech than ALC. In fact, one amp manufacturer says "run the transmitter at full power and let the Smart ALC in the amplifier adjust the required drive accordingly via the ALC signal". Oh wow! Certainly asking for trouble in my thinking. In my world of audio, ALC is much like limiting with an input to output ratio of 20:1. This says a 20 dB increase on the input causes only a 1 dB change in output. Now enter compression, where the input to output ratio is anywhere from 1:3 to about 10:3. Again a 10 dB input change yields a 3 dB output. Of course there are different attack times and release times applied to both limiting and compression. Newer technology systems have the ability to analyze the various components of the input signal and adjust the attack and release times quite effectively. Many Speech Processing algorithms have the same ability. Thus they are better suited for raising average PEP output. A second factor existing is the issue where hams like to see their power meter indicate the rated transceiver power. With some of the electronic power measuring devices that may work OK. However, with mechanical power indicating devices, the ballistics of the meter movement, meaning the slow response and overshoot damping, will not allow a mechanical meter to correctly show the energy level of ones SSB voice signal. The typical mechanical movement shows about -6 dB less or 25 watts for a 100 watt PEP signal. Of course speech processing will raise the average PEP level, but again the true PEP remains at 100 watts. And as Paul Harvey would say; "and now you know the rest of the story". 73 Bob, K4TAX On 1/31/2022 9:01 PM, elecraft-requ...@mailman.qth.net wrote: On Jan 30, 2022, at 1:10 PM, Fred Jensen 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 __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to arch...@mail-archive.com
Re: [Elecraft] What happened to ALC?
-Original Message- From: elecraft-boun...@mailman.qth.net On Behalf Of Fred Jensen Sent: Sunday, January 30, 2022 4:10 PM To: Elecraft Reflector Subject: [Elecraft] What happened to ALC? 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... >>> Maybe I'm not well-versed in today's whiz-bang technology, but to this old sound engineer this sounds suspiciously like compression. Jim - WS6X __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to arch...@mail-archive.com
Re: [Elecraft] What happened to ALC?
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 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 > > > > -- > This email has been checked for viruses by AVG. > https://www.avg.com > __ > Elecraft mailing list > Home: http://mailman.qth.net/mailman/listinfo/elecraft > Help: http://mailman.qth.net/mmfaq.htm > Post: mailto:Elecraft@mailman.qth.net > > This list hosted by: http://www.qsl.net > Please help support this email list: http://www.qsl.net/donate.html > Message delivered to wun...@wunderwood.org __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to arch...@mail-archive.com
Re: [Elecraft] What happened to ALC?
I agree. From one old sound engineer to another... I see this as audio compression. Bob, WG9L On 1/30/2022 6:17 PM, ws6x@gmail.com wrote: -Original Message- From: elecraft-boun...@mailman.qth.net On Behalf Of Fred Jensen Sent: Sunday, January 30, 2022 4:10 PM To: Elecraft Reflector Subject: [Elecraft] What happened to ALC? 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... Maybe I'm not well-versed in today's whiz-bang technology, but to this old sound engineer this sounds suspiciously like compression. Jim - WS6X __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to w...@comcast.net __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to arch...@mail-archive.com
Re: [Elecraft] What happened to ALC?
It sure does. > -Original Message- > From: elecraft-boun...@mailman.qth.net On Behalf Of Fred Jensen > Sent: Sunday, January 30, 2022 4:10 PM > To: Elecraft Reflector > Subject: [Elecraft] What happened to ALC? > > 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... >>>> > Maybe I'm not well-versed in today's whiz-bang technology, but to this old > sound engineer this sounds suspiciously like compression. > Jim - WS6X > > __ > Elecraft mailing list > Home: http://mailman.qth.net/mailman/listinfo/elecraft > Help: http://mailman.qth.net/mmfaq.htm > Post: mailto:Elecraft@mailman.qth.net > > This list hosted by: http://www.qsl.net > Please help support this email list: http://www.qsl.net/donate.html > Message delivered to g...@seanet.com > __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to arch...@mail-archive.com
Re: [Elecraft] What happened to ALC?
ALC is supposed to be linear, non-distorting. Change the level without changing the waveform. Compression is non-linear and changes (distorts) the waveform. I’ve read that the K3 uses RF limiting at the first IF for compression. If so, the ALC would be before the modulator and compression after it. wunder K6WRU Walter Underwood CM87wj http://observer.wunderwood.org/ (my blog) > On Jan 31, 2022, at 5:32 AM, Bob Schwerdlin wrote: > > I agree. From one old sound engineer to another... I see this as audio > compression. > > Bob, WG9L > > On 1/30/2022 6:17 PM, ws6x@gmail.com wrote: >> -Original Message- >> From: elecraft-boun...@mailman.qth.net On Behalf Of Fred Jensen >> Sent: Sunday, January 30, 2022 4:10 PM >> To: Elecraft Reflector >> Subject: [Elecraft] What happened to ALC? >> >> 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... >> Maybe I'm not well-versed in today's whiz-bang technology, but to this old >> sound engineer this sounds suspiciously like compression. >> Jim - WS6X >> >> __ >> Elecraft mailing list >> Home: http://mailman.qth.net/mailman/listinfo/elecraft >> Help: http://mailman.qth.net/mmfaq.htm >> Post: mailto:Elecraft@mailman.qth.net >> >> This list hosted by: http://www.qsl.net >> Please help support this email list: http://www.qsl.net/donate.html >> Message delivered to w...@comcast.net > > __ > Elecraft mailing list > Home: http://mailman.qth.net/mailman/listinfo/elecraft > Help: http://mailman.qth.net/mmfaq.htm > Post: mailto:Elecraft@mailman.qth.net > > This list hosted by: http://www.qsl.net > Please help support this email list: http://www.qsl.net/donate.html > Message delivered to wun...@wunderwood.org __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to arch...@mail-archive.com
Re: [Elecraft] What happened to ALC?
"If so, the ALC would be before the modulator and compression after it." I remember modulators but there isn't one in my TS-590. I doubt there is one in any modern rig. In the TS-590 architecture compression is done in DSP (Digital Signal Processing) and ALC is applied way down path at a TX IF amplifier. ALC gets a bad rap but it is alive and well in Kenwood rigs. It works without introducing signal distortion or harmonics. Having said that, I do not use external ALC with my KPA500. Andy, k3wyc __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to arch...@mail-archive.com
Re: [Elecraft] What happened to ALC?
“The modulator” means “the modulator code in the DSP” of course. If the compression is done by RF limiting, I expect that is also done in the DSP. The ALC you are describing is transmitter gain ALC. That is different from audio gain ALC. wunder K6WRU Walter Underwood CM87wj http://observer.wunderwood.org/ (my blog) > On Jan 31, 2022, at 12:07 PM, Andy Durbin wrote: > > "If so, the ALC would be before the modulator and compression after it." > > I remember modulators but there isn't one in my TS-590. I doubt there is > one in any modern rig. In the TS-590 architecture compression is done in DSP > (Digital Signal Processing) and ALC is applied way down path at a TX IF > amplifier. > > ALC gets a bad rap but it is alive and well in Kenwood rigs. It works > without introducing signal distortion or harmonics. Having said that, I do > not use external ALC with my KPA500. > > Andy, k3wyc > __ > Elecraft mailing list > Home: http://mailman.qth.net/mailman/listinfo/elecraft > Help: http://mailman.qth.net/mmfaq.htm > Post: mailto:Elecraft@mailman.qth.net > > This list hosted by: http://www.qsl.net > Please help support this email list: http://www.qsl.net/donate.html > Message delivered to wun...@wunderwood.org __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to arch...@mail-archive.com
Re: [Elecraft] What happened to ALC?
Not sure I see the difference. AVC [now called AGC aka audio compression], at it's simplest rectifies the audio from the detector and uses it as variable bias on one or more of the IF stages such that the IF gain is inversely proportional to the audio level. The original goal was to provide a constant volume in the presence of a fading RF signal. The K3 takes that concept to exceptional heights of course with multiple attack times, thresholds, slopes, and release times, maybe a tad too many for folks like me. ALC, at its simplest rectifies the RF at the input to the PA and feeds the variable DC back into the transmit chain to control the power applied to the PA with the goal of preventing PA saturation. Both introduce distortion by the very fact that they modify the waveform of the original signal. Both reduce the dynamic range of the transmitted signal, that is, both increase the average energy in the RF envelope. The original question however was simply, "If ALC was so great at reducing the effects of PA saturation in the early days of SSB, why isn't it that great now?" Granted, one manufacturer's amplifier may not feed back the correct varying DC levels to another manufacturer's transceiver, but that's just adjustment. Around the time SSB was being born, most [or maybe nearly all] AM broadcast stations ran at least two audio limiters in the chain to the transmitter. The first had a fairly short time constant and sort of shaved off the peaks. The second ["Sta-Level"] had a much longer time constant and responded to the average audio level. The result was modulation that hung around 100% all the time. AM broadcast has changed a lot since then and I don't know for sure if they are as heavily limited, but listening to several local ones, they sure sound like they have almost zero dynamic range. 73, Fred ["Skip"] K6DGW Sparks NV DM09dn Washoe County Walter Underwood wrote on 1/30/2022 5:07 PM: 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) -- This email has been checked for viruses by AVG. https://www.avg.com __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to arch...@mail-archive.com
